Cross-Referenced Linux and Device Driver Code

   /*
    *  linux/kernel/signal.c
    *
    *  Copyright (C) 1991, 1992  Linus Torvalds
    *
    *  1997-11-02  Modified for POSIX.1b signals by Richard Henderson
    *
    *  2003-06-02  Jim Houston - Concurrent Computer Corp.
    *              Changes to use preallocated sigqueue structures
   *              to allow signals to be sent reliably.
   */
  
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/sched.h>
  #include <linux/fs.h>
  #include <linux/tty.h>
  #include <linux/binfmts.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/ptrace.h>
  #include <linux/signal.h>
  #include <linux/signalfd.h>
  #include <linux/capability.h>
  #include <linux/freezer.h>
  #include <linux/pid_namespace.h>
  #include <linux/nsproxy.h>
  
  #include <asm/param.h>
  #include <asm/uaccess.h>
  #include <asm/unistd.h>
  #include <asm/siginfo.h>
  #include "audit.h"      /* audit_signal_info() */
  
  /*
   * SLAB caches for signal bits.
   */
  
  static struct kmem_cache *sigqueue_cachep;
  
  
  static int sig_ignored(struct task_struct *t, int sig)
  {
          void __user * handler;
  
          /*
           * Tracers always want to know about signals..
           */
          if (t->ptrace & PT_PTRACED)
                  return 0;
  
          /*
           * Blocked signals are never ignored, since the
           * signal handler may change by the time it is
           * unblocked.
           */
          if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
                  return 0;
  
          /* Is it explicitly or implicitly ignored? */
          handler = t->sighand->action[sig-1].sa.sa_handler;
          return   handler == SIG_IGN ||
                  (handler == SIG_DFL && sig_kernel_ignore(sig));
  }
  
  /*
   * Re-calculate pending state from the set of locally pending
   * signals, globally pending signals, and blocked signals.
   */
  static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
  {
          unsigned long ready;
          long i;
  
          switch (_NSIG_WORDS) {
          default:
                  for (i = _NSIG_WORDS, ready = 0; --i >= 0 ;)
                          ready |= signal->sig[i] &~ blocked->sig[i];
                  break;
  
          case 4: ready  = signal->sig[3] &~ blocked->sig[3];
                  ready |= signal->sig[2] &~ blocked->sig[2];
                  ready |= signal->sig[1] &~ blocked->sig[1];
                  ready |= signal->sig[0] &~ blocked->sig[0];
                  break;
  
          case 2: ready  = signal->sig[1] &~ blocked->sig[1];
                  ready |= signal->sig[0] &~ blocked->sig[0];
                  break;
  
          case 1: ready  = signal->sig[0] &~ blocked->sig[0];
          }
          return ready != 0;
  }
  
  #define PENDING(p,b) has_pending_signals(&(p)->signal, (b))
  
  static int recalc_sigpending_tsk(struct task_struct *t)
 {
         if (t->signal->group_stop_count > 0 ||
             PENDING(&t->pending, &t->blocked) ||
             PENDING(&t->signal->shared_pending, &t->blocked)) {
                 set_tsk_thread_flag(t, TIF_SIGPENDING);
                 return 1;
         }
         /*
          * We must never clear the flag in another thread, or in current
          * when it's possible the current syscall is returning -ERESTART*.
          * So we don't clear it here, and only callers who know they should do.
          */
         return 0;
 }
 
 /*
  * After recalculating TIF_SIGPENDING, we need to make sure the task wakes up.
  * This is superfluous when called on current, the wakeup is a harmless no-op.
  */
 void recalc_sigpending_and_wake(struct task_struct *t)
 {
         if (recalc_sigpending_tsk(t))
                 signal_wake_up(t, 0);
 }
 
 void recalc_sigpending(void)
 {
         if (!recalc_sigpending_tsk(current) && !freezing(current))
                 clear_thread_flag(TIF_SIGPENDING);
 
 }
 
 /* Given the mask, find the first available signal that should be serviced. */
 
 int next_signal(struct sigpending *pending, sigset_t *mask)
 {
         unsigned long i, *s, *m, x;
         int sig = 0;
         
         s = pending->signal.sig;
         m = mask->sig;
         switch (_NSIG_WORDS) {
         default:
                 for (i = 0; i < _NSIG_WORDS; ++i, ++s, ++m)
                         if ((x = *s &~ *m) != 0) {
                                 sig = ffz(~x) + i*_NSIG_BPW + 1;
                                 break;
                         }
                 break;
 
         case 2: if ((x = s[0] &~ m[0]) != 0)
                         sig = 1;
                 else if ((x = s[1] &~ m[1]) != 0)
                         sig = _NSIG_BPW + 1;
                 else
                         break;
                 sig += ffz(~x);
                 break;
 
         case 1: if ((x = *s &~ *m) != 0)
                         sig = ffz(~x) + 1;
                 break;
         }
         
         return sig;
 }
 
 static struct sigqueue *__sigqueue_alloc(struct task_struct *t, gfp_t flags,
                                          int override_rlimit)
 {
         struct sigqueue *q = NULL;
         struct user_struct *user;
 
         /*
          * In order to avoid problems with "switch_user()", we want to make
          * sure that the compiler doesn't re-load "t->user"
          */
         user = t->user;
         barrier();
         atomic_inc(&user->sigpending);
         if (override_rlimit ||
             atomic_read(&user->sigpending) <=
                         t->signal->rlim[RLIMIT_SIGPENDING].rlim_cur)
                 q = kmem_cache_alloc(sigqueue_cachep, flags);
         if (unlikely(q == NULL)) {
                 atomic_dec(&user->sigpending);
         } else {
                 INIT_LIST_HEAD(&q->list);
                 q->flags = 0;
                 q->user = get_uid(user);
         }
         return(q);
 }
 
 static void __sigqueue_free(struct sigqueue *q)
 {
         if (q->flags & SIGQUEUE_PREALLOC)
                 return;
         atomic_dec(&q->user->sigpending);
         free_uid(q->user);
         kmem_cache_free(sigqueue_cachep, q);
 }
 
 void flush_sigqueue(struct sigpending *queue)
 {
         struct sigqueue *q;
 
         sigemptyset(&queue->signal);
         while (!list_empty(&queue->list)) {
                 q = list_entry(queue->list.next, struct sigqueue , list);
                 list_del_init(&q->list);
                 __sigqueue_free(q);
         }
 }
 
 /*
  * Flush all pending signals for a task.
  */
 void flush_signals(struct task_struct *t)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&t->sighand->siglock, flags);
         clear_tsk_thread_flag(t,TIF_SIGPENDING);
         flush_sigqueue(&t->pending);
         flush_sigqueue(&t->signal->shared_pending);
         spin_unlock_irqrestore(&t->sighand->siglock, flags);
 }
 
 void ignore_signals(struct task_struct *t)
 {
         int i;
 
         for (i = 0; i < _NSIG; ++i)
                 t->sighand->action[i].sa.sa_handler = SIG_IGN;
 
         flush_signals(t);
 }
 
 /*
  * Flush all handlers for a task.
  */
 
 void
 flush_signal_handlers(struct task_struct *t, int force_default)
 {
         int i;
         struct k_sigaction *ka = &t->sighand->action[0];
         for (i = _NSIG ; i != 0 ; i--) {
                 if (force_default || ka->sa.sa_handler != SIG_IGN)
                         ka->sa.sa_handler = SIG_DFL;
                 ka->sa.sa_flags = 0;
                 sigemptyset(&ka->sa.sa_mask);
                 ka++;
         }
 }
 
 int unhandled_signal(struct task_struct *tsk, int sig)
 {
         if (is_global_init(tsk))
                 return 1;
         if (tsk->ptrace & PT_PTRACED)
                 return 0;
         return (tsk->sighand->action[sig-1].sa.sa_handler == SIG_IGN) ||
                 (tsk->sighand->action[sig-1].sa.sa_handler == SIG_DFL);
 }
 
 
 /* Notify the system that a driver wants to block all signals for this
  * process, and wants to be notified if any signals at all were to be
  * sent/acted upon.  If the notifier routine returns non-zero, then the
  * signal will be acted upon after all.  If the notifier routine returns 0,
  * then then signal will be blocked.  Only one block per process is
  * allowed.  priv is a pointer to private data that the notifier routine
  * can use to determine if the signal should be blocked or not.  */
 
 void
 block_all_signals(int (*notifier)(void *priv), void *priv, sigset_t *mask)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&current->sighand->siglock, flags);
         current->notifier_mask = mask;
         current->notifier_data = priv;
         current->notifier = notifier;
         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 }
 
 /* Notify the system that blocking has ended. */
 
 void
 unblock_all_signals(void)
 {
         unsigned long flags;
 
         spin_lock_irqsave(&current->sighand->siglock, flags);
         current->notifier = NULL;
         current->notifier_data = NULL;
         recalc_sigpending();
         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 }
 
 static int collect_signal(int sig, struct sigpending *list, siginfo_t *info)
 {
         struct sigqueue *q, *first = NULL;
         int still_pending = 0;
 
         if (unlikely(!sigismember(&list->signal, sig)))
                 return 0;
 
         /*
          * Collect the siginfo appropriate to this signal.  Check if
          * there is another siginfo for the same signal.
         */
         list_for_each_entry(q, &list->list, list) {
                 if (q->info.si_signo == sig) {
                         if (first) {
                                 still_pending = 1;
                                 break;
                         }
                         first = q;
                 }
         }
         if (first) {
                 list_del_init(&first->list);
                 copy_siginfo(info, &first->info);
                 __sigqueue_free(first);
                 if (!still_pending)
                         sigdelset(&list->signal, sig);
         } else {
 
                 /* Ok, it wasn't in the queue.  This must be
                    a fast-pathed signal or we must have been
                    out of queue space.  So zero out the info.
                  */
                 sigdelset(&list->signal, sig);
                 info->si_signo = sig;
                 info->si_errno = 0;
                 info->si_code = 0;
                 info->si_pid = 0;
                 info->si_uid = 0;
         }
         return 1;
 }
 
 static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
                         siginfo_t *info)
 {
         int sig = next_signal(pending, mask);
 
         if (sig) {
                 if (current->notifier) {
                         if (sigismember(current->notifier_mask, sig)) {
                                 if (!(current->notifier)(current->notifier_data)) {
                                         clear_thread_flag(TIF_SIGPENDING);
                                         return 0;
                                 }
                         }
                 }
 
                 if (!collect_signal(sig, pending, info))
                         sig = 0;
         }
 
         return sig;
 }
 
 /*
  * Dequeue a signal and return the element to the caller, which is 
  * expected to free it.
  *
  * All callers have to hold the siglock.
  */
 int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
 {
         int signr = 0;
 
         /* We only dequeue private signals from ourselves, we don't let
          * signalfd steal them
          */
         signr = __dequeue_signal(&tsk->pending, mask, info);
         if (!signr) {
                 signr = __dequeue_signal(&tsk->signal->shared_pending,
                                          mask, info);
                 /*
                  * itimer signal ?
                  *
                  * itimers are process shared and we restart periodic
                  * itimers in the signal delivery path to prevent DoS
                  * attacks in the high resolution timer case. This is
                  * compliant with the old way of self restarting
                  * itimers, as the SIGALRM is a legacy signal and only
                  * queued once. Changing the restart behaviour to
                  * restart the timer in the signal dequeue path is
                  * reducing the timer noise on heavy loaded !highres
                  * systems too.
                  */
                 if (unlikely(signr == SIGALRM)) {
                         struct hrtimer *tmr = &tsk->signal->real_timer;
 
                         if (!hrtimer_is_queued(tmr) &&
                             tsk->signal->it_real_incr.tv64 != 0) {
                                 hrtimer_forward(tmr, tmr->base->get_time(),
                                                 tsk->signal->it_real_incr);
                                 hrtimer_restart(tmr);
                         }
                 }
         }
         recalc_sigpending();
         if (signr && unlikely(sig_kernel_stop(signr))) {
                 /*
                  * Set a marker that we have dequeued a stop signal.  Our
                  * caller might release the siglock and then the pending
                  * stop signal it is about to process is no longer in the
                  * pending bitmasks, but must still be cleared by a SIGCONT
                  * (and overruled by a SIGKILL).  So those cases clear this
                  * shared flag after we've set it.  Note that this flag may
                  * remain set after the signal we return is ignored or
                  * handled.  That doesn't matter because its only purpose
                  * is to alert stop-signal processing code when another
                  * processor has come along and cleared the flag.
                  */
                 if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT))
                         tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
         }
         if (signr &&
              ((info->si_code & __SI_MASK) == __SI_TIMER) &&
              info->si_sys_private){
                 /*
                  * Release the siglock to ensure proper locking order
                  * of timer locks outside of siglocks.  Note, we leave
                  * irqs disabled here, since the posix-timers code is
                  * about to disable them again anyway.
                  */
                 spin_unlock(&tsk->sighand->siglock);
                 do_schedule_next_timer(info);
                 spin_lock(&tsk->sighand->siglock);
         }
         return signr;
 }
 
 /*
  * Tell a process that it has a new active signal..
  *
  * NOTE! we rely on the previous spin_lock to
  * lock interrupts for us! We can only be called with
  * "siglock" held, and the local interrupt must
  * have been disabled when that got acquired!
  *
  * No need to set need_resched since signal event passing
  * goes through ->blocked
  */
 void signal_wake_up(struct task_struct *t, int resume)
 {
         unsigned int mask;
 
         set_tsk_thread_flag(t, TIF_SIGPENDING);
 
         /*
          * For SIGKILL, we want to wake it up in the stopped/traced/killable
          * case. We don't check t->state here because there is a race with it
          * executing another processor and just now entering stopped state.
          * By using wake_up_state, we ensure the process will wake up and
          * handle its death signal.
          */
         mask = TASK_INTERRUPTIBLE;
         if (resume)
                 mask |= TASK_WAKEKILL;
         if (!wake_up_state(t, mask))
                 kick_process(t);
 }
 
 /*
  * Remove signals in mask from the pending set and queue.
  * Returns 1 if any signals were found.
  *
  * All callers must be holding the siglock.
  *
  * This version takes a sigset mask and looks at all signals,
  * not just those in the first mask word.
  */
 static int rm_from_queue_full(sigset_t *mask, struct sigpending *s)
 {
         struct sigqueue *q, *n;
         sigset_t m;
 
         sigandsets(&m, mask, &s->signal);
         if (sigisemptyset(&m))
                 return 0;
 
         signandsets(&s->signal, &s->signal, mask);
         list_for_each_entry_safe(q, n, &s->list, list) {
                 if (sigismember(mask, q->info.si_signo)) {
                         list_del_init(&q->list);
                         __sigqueue_free(q);
                 }
         }
         return 1;
 }
 /*
  * Remove signals in mask from the pending set and queue.
  * Returns 1 if any signals were found.
  *
  * All callers must be holding the siglock.
  */
 static int rm_from_queue(unsigned long mask, struct sigpending *s)
 {
         struct sigqueue *q, *n;
 
         if (!sigtestsetmask(&s->signal, mask))
                 return 0;
 
         sigdelsetmask(&s->signal, mask);
         list_for_each_entry_safe(q, n, &s->list, list) {
                 if (q->info.si_signo < SIGRTMIN &&
                     (mask & sigmask(q->info.si_signo))) {
                         list_del_init(&q->list);
                         __sigqueue_free(q);
                 }
         }
         return 1;
 }
 
 /*
  * Bad permissions for sending the signal
  */
 static int check_kill_permission(int sig, struct siginfo *info,
                                  struct task_struct *t)
 {
         int error = -EINVAL;
         if (!valid_signal(sig))
                 return error;
 
         if (info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info))) {
                 error = audit_signal_info(sig, t); /* Let audit system see the signal */
                 if (error)
                         return error;
                 error = -EPERM;
                 if (((sig != SIGCONT) ||
                         (task_session_nr(current) != task_session_nr(t)))
                     && (current->euid ^ t->suid) && (current->euid ^ t->uid)
                     && (current->uid ^ t->suid) && (current->uid ^ t->uid)
                     && !capable(CAP_KILL))
                 return error;
         }
 
         return security_task_kill(t, info, sig, 0);
 }
 
 /* forward decl */
 static void do_notify_parent_cldstop(struct task_struct *tsk, int why);
 
 /*
  * Handle magic process-wide effects of stop/continue signals.
  * Unlike the signal actions, these happen immediately at signal-generation
  * time regardless of blocking, ignoring, or handling.  This does the
  * actual continuing for SIGCONT, but not the actual stopping for stop
  * signals.  The process stop is done as a signal action for SIG_DFL.
  */
 static void handle_stop_signal(int sig, struct task_struct *p)
 {
         struct task_struct *t;
 
         if (p->signal->flags & SIGNAL_GROUP_EXIT)
                 /*
                  * The process is in the middle of dying already.
                  */
                 return;
 
         if (sig_kernel_stop(sig)) {
                 /*
                  * This is a stop signal.  Remove SIGCONT from all queues.
                  */
                 rm_from_queue(sigmask(SIGCONT), &p->signal->shared_pending);
                 t = p;
                 do {
                         rm_from_queue(sigmask(SIGCONT), &t->pending);
                         t = next_thread(t);
                 } while (t != p);
         } else if (sig == SIGCONT) {
                 /*
                  * Remove all stop signals from all queues,
                  * and wake all threads.
                  */
                 if (unlikely(p->signal->group_stop_count > 0)) {
                         /*
                          * There was a group stop in progress.  We'll
                          * pretend it finished before we got here.  We are
                          * obliged to report it to the parent: if the
                          * SIGSTOP happened "after" this SIGCONT, then it
                          * would have cleared this pending SIGCONT.  If it
                          * happened "before" this SIGCONT, then the parent
                          * got the SIGCHLD about the stop finishing before
                          * the continue happened.  We do the notification
                          * now, and it's as if the stop had finished and
                          * the SIGCHLD was pending on entry to this kill.
                          */
                         p->signal->group_stop_count = 0;
                         p->signal->flags = SIGNAL_STOP_CONTINUED;
                         spin_unlock(&p->sighand->siglock);
                         do_notify_parent_cldstop(p, CLD_STOPPED);
                         spin_lock(&p->sighand->siglock);
                 }
                 rm_from_queue(SIG_KERNEL_STOP_MASK, &p->signal->shared_pending);
                 t = p;
                 do {
                         unsigned int state;
                         rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
                         
                         /*
                          * If there is a handler for SIGCONT, we must make
                          * sure that no thread returns to user mode before
                          * we post the signal, in case it was the only
                          * thread eligible to run the signal handler--then
                          * it must not do anything between resuming and
                          * running the handler.  With the TIF_SIGPENDING
                          * flag set, the thread will pause and acquire the
                          * siglock that we hold now and until we've queued
                          * the pending signal. 
                          *
                          * Wake up the stopped thread _after_ setting
                          * TIF_SIGPENDING
                          */
                         state = __TASK_STOPPED;
                         if (sig_user_defined(t, SIGCONT) && !sigismember(&t->blocked, SIGCONT)) {
                                 set_tsk_thread_flag(t, TIF_SIGPENDING);
                                 state |= TASK_INTERRUPTIBLE;
                         }
                         wake_up_state(t, state);
 
                         t = next_thread(t);
                 } while (t != p);
 
                 if (p->signal->flags & SIGNAL_STOP_STOPPED) {
                         /*
                          * We were in fact stopped, and are now continued.
                          * Notify the parent with CLD_CONTINUED.
                          */
                         p->signal->flags = SIGNAL_STOP_CONTINUED;
                         p->signal->group_exit_code = 0;
                         spin_unlock(&p->sighand->siglock);
                         do_notify_parent_cldstop(p, CLD_CONTINUED);
                         spin_lock(&p->sighand->siglock);
                 } else {
                         /*
                          * We are not stopped, but there could be a stop
                          * signal in the middle of being processed after
                          * being removed from the queue.  Clear that too.
                          */
                         p->signal->flags = 0;
                 }
         } else if (sig == SIGKILL) {
                 /*
                  * Make sure that any pending stop signal already dequeued
                  * is undone by the wakeup for SIGKILL.
                  */
                 p->signal->flags = 0;
         }
 }
 
 static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
                         struct sigpending *signals)
 {
         struct sigqueue * q = NULL;
         int ret = 0;
 
         /*
          * Deliver the signal to listening signalfds. This must be called
          * with the sighand lock held.
          */
         signalfd_notify(t, sig);
 
         /*
          * fast-pathed signals for kernel-internal things like SIGSTOP
          * or SIGKILL.
          */
         if (info == SEND_SIG_FORCED)
                 goto out_set;
 
         /* Real-time signals must be queued if sent by sigqueue, or
            some other real-time mechanism.  It is implementation
            defined whether kill() does so.  We attempt to do so, on
            the principle of least surprise, but since kill is not
            allowed to fail with EAGAIN when low on memory we just
            make sure at least one signal gets delivered and don't
            pass on the info struct.  */
 
         q = __sigqueue_alloc(t, GFP_ATOMIC, (sig < SIGRTMIN &&
                                              (is_si_special(info) ||
                                               info->si_code >= 0)));
         if (q) {
                 list_add_tail(&q->list, &signals->list);
                 switch ((unsigned long) info) {
                 case (unsigned long) SEND_SIG_NOINFO:
                         q->info.si_signo = sig;
                         q->info.si_errno = 0;
                         q->info.si_code = SI_USER;
                         q->info.si_pid = task_pid_vnr(current);
                         q->info.si_uid = current->uid;
                         break;
                 case (unsigned long) SEND_SIG_PRIV:
                         q->info.si_signo = sig;
                         q->info.si_errno = 0;
                         q->info.si_code = SI_KERNEL;
                         q->info.si_pid = 0;
                         q->info.si_uid = 0;
                         break;
                 default:
                         copy_siginfo(&q->info, info);
                         break;
                 }
         } else if (!is_si_special(info)) {
                 if (sig >= SIGRTMIN && info->si_code != SI_USER)
                 /*
                  * Queue overflow, abort.  We may abort if the signal was rt
                  * and sent by user using something other than kill().
                  */
                         return -EAGAIN;
         }
 
 out_set:
         sigaddset(&signals->signal, sig);
         return ret;
 }
 
 #define LEGACY_QUEUE(sigptr, sig) \
         (((sig) < SIGRTMIN) && sigismember(&(sigptr)->signal, (sig)))
 
 int print_fatal_signals;
 
 static void print_fatal_signal(struct pt_regs *regs, int signr)
 {
         printk("%s/%d: potentially unexpected fatal signal %d.\n",
                 current->comm, task_pid_nr(current), signr);
 
 #if defined(__i386__) && !defined(__arch_um__)
         printk("code at %08lx: ", regs->ip);
         {
                 int i;
                 for (i = 0; i < 16; i++) {
                         unsigned char insn;
 
                         __get_user(insn, (unsigned char *)(regs->ip + i));
                         printk("%02x ", insn);
                 }
         }
 #endif
         printk("\n");
         show_regs(regs);
 }
 
 static int __init setup_print_fatal_signals(char *str)
 {
         get_option (&str, &print_fatal_signals);
 
         return 1;
 }
 
 __setup("print-fatal-signals=", setup_print_fatal_signals);
 
 static int
 specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
 {
         int ret = 0;
 
         BUG_ON_NONRT(!irqs_disabled());
 #ifdef CONFIG_SMP
         assert_spin_locked(&t->sighand->siglock);
 #endif
 
         /* Short-circuit ignored signals.  */
         if (sig_ignored(t, sig))
                 goto out;
 
         /* Support queueing exactly one non-rt signal, so that we
            can get more detailed information about the cause of
            the signal. */
         if (LEGACY_QUEUE(&t->pending, sig))
                 goto out;
 
         ret = send_signal(sig, info, t, &t->pending);
         if (!ret && !sigismember(&t->blocked, sig))
                 signal_wake_up(t, sig == SIGKILL);
 out:
         return ret;
 }
 
 /*
  * Force a signal that the process can't ignore: if necessary
  * we unblock the signal and change any SIG_IGN to SIG_DFL.
  *
  * Note: If we unblock the signal, we always reset it to SIG_DFL,
  * since we do not want to have a signal handler that was blocked
  * be invoked when user space had explicitly blocked it.
  *
  * We don't want to have recursive SIGSEGV's etc, for example.
  */
 int
 force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
 {
         unsigned long int flags;
         int ret, blocked, ignored;
         struct k_sigaction *action;
 
         spin_lock_irqsave(&t->sighand->siglock, flags);
         action = &t->sighand->action[sig-1];
         ignored = action->sa.sa_handler == SIG_IGN;
         blocked = sigismember(&t->blocked, sig);
         if (blocked || ignored) {
                 action->sa.sa_handler = SIG_DFL;
                 if (blocked) {
                         sigdelset(&t->blocked, sig);
                         recalc_sigpending_and_wake(t);
                 }
         }
         ret = specific_send_sig_info(sig, info, t);
         spin_unlock_irqrestore(&t->sighand->siglock, flags);
 
         return ret;
 }
 
 void
 force_sig_specific(int sig, struct task_struct *t)
 {
         force_sig_info(sig, SEND_SIG_FORCED, t);
 }
 
 /*
  * Test if P wants to take SIG.  After we've checked all threads with this,
  * it's equivalent to finding no threads not blocking SIG.  Any threads not
  * blocking SIG were ruled out because they are not running and already
  * have pending signals.  Such threads will dequeue from the shared queue
  * as soon as they're available, so putting the signal on the shared queue
  * will be equivalent to sending it to one such thread.
  */
 static inline int wants_signal(int sig, struct task_struct *p)
 {
         if (sigismember(&p->blocked, sig))
                 return 0;
         if (p->flags & PF_EXITING)
                 return 0;
         if (sig == SIGKILL)
                 return 1;
         if (task_is_stopped_or_traced(p))
                 return 0;
         return task_curr(p) || !signal_pending(p);
 }
 
 static void
 __group_complete_signal(int sig, struct task_struct *p)
 {
         struct task_struct *t;
 
         /*
          * Now find a thread we can wake up to take the signal off the queue.
          *
          * If the main thread wants the signal, it gets first crack.
          * Probably the least surprising to the average bear.
          */
         if (wants_signal(sig, p))
                 t = p;
         else if (thread_group_empty(p))
                 /*
                  * There is just one thread and it does not need to be woken.
                  * It will dequeue unblocked signals before it runs again.
                  */
                 return;
         else {
                 /*
                  * Otherwise try to find a suitable thread.
                  */
                 t = p->signal->curr_target;
                 if (t == NULL)
                         /* restart balancing at this thread */
                         t = p->signal->curr_target = p;
 
                 while (!wants_signal(sig, t)) {
                         t = next_thread(t);
                         if (t == p->signal->curr_target)
                                 /*
                                  * No thread needs to be woken.
                                  * Any eligible threads will see
                                  * the signal in the queue soon.
                                  */
                                 return;
                 }
                 p->signal->curr_target = t;
         }
 
         /*
          * Found a killable thread.  If the signal will be fatal,
          * then start taking the whole group down immediately.
          */
         if (sig_fatal(p, sig) && !(p->signal->flags & SIGNAL_GROUP_EXIT) &&
             !sigismember(&t->real_blocked, sig) &&
             (sig == SIGKILL || !(t->ptrace & PT_PTRACED))) {
                 /*
                  * This signal will be fatal to the whole group.
                  */
                 if (!sig_kernel_coredump(sig)) {
                         /*
                          * Start a group exit and wake everybody up.
                          * This way we don't have other threads
                          * running and doing things after a slower
                          * thread has the fatal signal pending.
                          */
                         p->signal->flags = SIGNAL_GROUP_EXIT;
                         p->signal->group_exit_code = sig;
                         p->signal->group_stop_count = 0;
                         t = p;
                         do {
                                 sigaddset(&t->pending.signal, SIGKILL);
                                 signal_wake_up(t, 1);
                         } while_each_thread(p, t);
                         return;
                 }
         }
 
         /*
          * The signal is already in the shared-pending queue.
          * Tell the chosen thread to wake up and dequeue it.
          */
         signal_wake_up(t, sig == SIGKILL);
         return;
 }
 
 int
 __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
         int ret = 0;
 
         assert_spin_locked(&p->sighand->siglock);
         handle_stop_signal(sig, p);
 
         /* Short-circuit ignored signals.  */
         if (sig_ignored(p, sig))
                 return ret;
 
         if (LEGACY_QUEUE(&p->signal->shared_pending, sig))
                 /* This is a non-RT signal and we already have one queued.  */
                 return ret;
 
         /*
          * Put this signal on the shared-pending queue, or fail with EAGAIN.
          * We always use the shared queue for process-wide signals,
          * to avoid several races.
          */
         ret = send_signal(sig, info, p, &p->signal->shared_pending);
         if (unlikely(ret))
                 return ret;
 
         __group_complete_signal(sig, p);
         return 0;
 }
 
 /*
  * Nuke all other threads in the group.
  */
 void zap_other_threads(struct task_struct *p)
 {
         struct task_struct *t;
 
         p->signal->group_stop_count = 0;
 
         for (t = next_thread(p); t != p; t = next_thread(t)) {
                 /*
                  * Don't bother with already dead threads
                  */
                 if (t->exit_state)
                         continue;
 
                 /* SIGKILL will be handled before any pending SIGSTOP */
                 sigaddset(&t->pending.signal, SIGKILL);
                 signal_wake_up(t, 1);
         }
 }
 
 int __fatal_signal_pending(struct task_struct *tsk)
 {
         return sigismember(&tsk->pending.signal, SIGKILL);
 }
 EXPORT_SYMBOL(__fatal_signal_pending);
 
 /*
  * Must be called under rcu_read_lock() or with tasklist_lock read-held.
  */
 struct sighand_struct *lock_task_sighand(struct task_struct *tsk, unsigned long *flags)
 {
         struct sighand_struct *sighand;
 
         for (;;) {
                 sighand = rcu_dereference(tsk->sighand);
                 if (unlikely(sighand == NULL))
                         break;
 
                 spin_lock_irqsave(&sighand->siglock, *flags);
                 if (likely(sighand == tsk->sighand))
                         break;
                 spin_unlock_irqrestore(&sighand->siglock, *flags);
         }
 
         return sighand;
 }
 
 int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
         unsigned long flags;
         int ret;
 
         ret = check_kill_permission(sig, info, p);
 
         if (!ret && sig) {
                 ret = -ESRCH;
                 if (lock_task_sighand(p, &flags)) {
                         ret = __group_send_sig_info(sig, info, p);
                         unlock_task_sighand(p, &flags);
                 }
         }
 
         return ret;
 }
 
 /*
  * __kill_pgrp_info() sends a signal to a process group: this is what the tty
  * control characters do (^C, ^Z etc)
  */
 
 int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp)
 {
         struct task_struct *p = NULL;
         int retval, success;
 
         success = 0;
         retval = -ESRCH;
         do_each_pid_task(pgrp, PIDTYPE_PGID, p) {
                 int err = group_send_sig_info(sig, info, p);
                 success |= !err;
                 retval = err;
         } while_each_pid_task(pgrp, PIDTYPE_PGID, p);
         return success ? 0 : retval;
 }
 
 int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
 {
         int error = -ESRCH;
         struct task_struct *p;
 
         rcu_read_lock();
         if (unlikely(sig_needs_tasklist(sig)))
                 read_lock(&tasklist_lock);
 
 retry:
         p = pid_task(pid, PIDTYPE_PID);
         if (p) {
                 error = group_send_sig_info(sig, info, p);
                 if (unlikely(error == -ESRCH))
                         /*
                          * The task was unhashed in between, try again.
                          * If it is dead, pid_task() will return NULL,
                          * if we race with de_thread() it will find the
                          * new leader.
                          */
                         goto retry;
         }
 
         if (unlikely(sig_needs_tasklist(sig)))
                 read_unlock(&tasklist_lock);
         rcu_read_unlock();
         return error;
 }
 
 int
 kill_proc_info(int sig, struct siginfo *info, pid_t pid)
 {
         int error;
         rcu_read_lock();
         error = kill_pid_info(sig, info, find_vpid(pid));
         rcu_read_unlock();
         return error;
 }
 
 /* like kill_pid_info(), but doesn't use uid/euid of "current" */
 int kill_pid_info_as_uid(int sig, struct siginfo *info, struct pid *pid,
                       uid_t uid, uid_t euid, u32 secid)
 {
         int ret = -EINVAL;
         struct task_struct *p;
 
         if (!valid_signal(sig))
                 return ret;
 
         read_lock(&tasklist_lock);
         p = pid_task(pid, PIDTYPE_PID);
         if (!p) {
                 ret = -ESRCH;
                 goto out_unlock;
         }
         if ((info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info)))
             && (euid != p->suid) && (euid != p->uid)
             && (uid != p->suid) && (uid != p->uid)) {
                 ret = -EPERM;
                 goto out_unlock;
         }
         ret = security_task_kill(p, info, sig, secid);
         if (ret)
                 goto out_unlock;
         if (sig && p->sighand) {
                 unsigned long flags;
                 spin_lock_irqsave(&p->sighand->siglock, flags);
                 ret = __group_send_sig_info(sig, info, p);
                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
         }
 out_unlock:
         read_unlock(&tasklist_lock);
         return ret;
 }
 EXPORT_SYMBOL_GPL(kill_pid_info_as_uid);
 
 /*
  * kill_something_info() interprets pid in interesting ways just like kill(2).
  *
  * POSIX specifies that kill(-1,sig) is unspecified, but what we have
  * is probably wrong.  Should make it like BSD or SYSV.
  */
 
 static int kill_something_info(int sig, struct siginfo *info, int pid)
 {
         int ret;
 
         if (pid > 0) {
                 rcu_read_lock();
                 ret = kill_pid_info(sig, info, find_vpid(pid));
                 rcu_read_unlock();
                 return ret;
         }
 
         read_lock(&tasklist_lock);
         if (pid != -1) {
                 ret = __kill_pgrp_info(sig, info,
                                 pid ? find_vpid(-pid) : task_pgrp(current));
         } else {
                 int retval = 0, count = 0;
                 struct task_struct * p;
 
                 for_each_process(p) {
                         if (p->pid > 1 && !same_thread_group(p, current)) {
                                 int err = group_send_sig_info(sig, info, p);
                                 ++count;
                                 if (err != -EPERM)
                                         retval = err;
                         }
                 }
                 ret = count ? retval : -ESRCH;
         }
         read_unlock(&tasklist_lock);
 
         return ret;
 }
 
 /*
  * These are for backward compatibility with the rest of the kernel source.
  */
 
 /*
  * These two are the most common entry points.  They send a signal
  * just to the specific thread.
  */
 int
 send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
         int ret;
         unsigned long flags;
 
         /*
          * Make sure legacy kernel users don't send in bad values
          * (normal paths check this in check_kill_permission).
          */
         if (!valid_signal(sig))
                 return -EINVAL;
 
         /*
          * We need the tasklist lock even for the specific
          * thread case (when we don't need to follow the group
          * lists) in order to avoid races with "p->sighand"
          * going away or changing from under us.
          */
         read_lock(&tasklist_lock);  
         spin_lock_irqsave(&p->sighand->siglock, flags);
         ret = specific_send_sig_info(sig, info, p);
         spin_unlock_irqrestore(&p->sighand->siglock, flags);
         read_unlock(&tasklist_lock);
         return ret;
 }
 
 #define __si_special(priv) \
         ((priv) ? SEND_SIG_PRIV : SEND_SIG_NOINFO)
 
 int
 send_sig(int sig, struct task_struct *p, int priv)
 {
         return send_sig_info(sig, __si_special(priv), p);
 }
 
 void
 force_sig(int sig, struct task_struct *p)
 {
         force_sig_info(sig, SEND_SIG_PRIV, p);
 }
 
 /*
  * When things go south during signal handling, we
  * will force a SIGSEGV. And if the signal that caused
  * the problem was already a SIGSEGV, we'll want to
  * make sure we don't even try to deliver the signal..
  */
 int
 force_sigsegv(int sig, struct task_struct *p)
 {
         if (sig == SIGSEGV) {
                 unsigned long flags;
                 spin_lock_irqsave(&p->sighand->siglock, flags);
                 p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
                 spin_unlock_irqrestore(&p->sighand->siglock, flags);
         }
         force_sig(SIGSEGV, p);
         return 0;
 }
 
 int kill_pgrp(struct pid *pid, int sig, int priv)
 {
         int ret;
 
         read_lock(&tasklist_lock);
         ret = __kill_pgrp_info(sig, __si_special(priv), pid);
         read_unlock(&tasklist_lock);
 
         return ret;
 }
 EXPORT_SYMBOL(kill_pgrp);
 
 int kill_pid(struct pid *pid, int sig, int priv)
 {
         return kill_pid_info(sig, __si_special(priv), pid);
 }
 EXPORT_SYMBOL(kill_pid);
 
 int
 kill_proc(pid_t pid, int sig, int priv)
 {
         int ret;
 
         rcu_read_lock();
         ret = kill_pid_info(sig, __si_special(priv), find_pid(pid));
         rcu_read_unlock();
         return ret;
 }
 
 /*
  * These functions support sending signals using preallocated sigqueue
  * structures.  This is needed "because realtime applications cannot
  * afford to lose notifications of asynchronous events, like timer
  * expirations or I/O completions".  In the case of Posix Timers 
  * we allocate the sigqueue structure from the timer_create.  If this
  * allocation fails we are able to report the failure to the application
  * with an EAGAIN error.
  */
  
 struct sigqueue *sigqueue_alloc(void)
 {
         struct sigqueue *q;
 
         if ((q = __sigqueue_alloc(current, GFP_KERNEL, 0)))
                 q->flags |= SIGQUEUE_PREALLOC;
         return(q);
 }
 
 void sigqueue_free(struct sigqueue *q)
 {
         unsigned long flags;
         spinlock_t *lock = &current->sighand->siglock;
 
         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
         /*
          * If the signal is still pending remove it from the
          * pending queue. We must hold ->siglock while testing
          * q->list to serialize with collect_signal().
          */
         spin_lock_irqsave(lock, flags);
         if (!list_empty(&q->list))
                 list_del_init(&q->list);
         spin_unlock_irqrestore(lock, flags);
 
         q->flags &= ~SIGQUEUE_PREALLOC;
         __sigqueue_free(q);
 }
 
 int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
 {
         unsigned long flags;
         int ret = 0;
 
         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
 
         /*
          * The rcu based delayed sighand destroy makes it possible to
          * run this without tasklist lock held. The task struct itself
          * cannot go away as create_timer did get_task_struct().
          *
          * We return -1, when the task is marked exiting, so
          * posix_timer_event can redirect it to the group leader
          */
         rcu_read_lock();
 
         if (!likely(lock_task_sighand(p, &flags))) {
                 ret = -1;
                 goto out_err;
         }
 
         if (unlikely(!list_empty(&q->list))) {
                 /*
                  * If an SI_TIMER entry is already queue just increment
                  * the overrun count.
                  */
                 BUG_ON(q->info.si_code != SI_TIMER);
                 q->info.si_overrun++;
                 goto out;
         }
         /* Short-circuit ignored signals.  */
         if (sig_ignored(p, sig)) {
                 ret = 1;
                 goto out;
         }
         /*
          * Deliver the signal to listening signalfds. This must be called
          * with the sighand lock held.
          */
         signalfd_notify(p, sig);
 
         list_add_tail(&q->list, &p->pending.list);
         sigaddset(&p->pending.signal, sig);
         if (!sigismember(&p->blocked, sig))
                 signal_wake_up(p, sig == SIGKILL);
 
 out:
         unlock_task_sighand(p, &flags);
 out_err:
         rcu_read_unlock();
 
         return ret;
 }
 
 int
 send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
 {
         unsigned long flags;
         int ret = 0;
 
         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
 
         read_lock(&tasklist_lock);
         /* Since it_lock is held, p->sighand cannot be NULL. */
         spin_lock_irqsave(&p->sighand->siglock, flags);
         handle_stop_signal(sig, p);
 
         /* Short-circuit ignored signals.  */
         if (sig_ignored(p, sig)) {
                 ret = 1;
                 goto out;
         }
 
         if (unlikely(!list_empty(&q->list))) {
                 /*
                  * If an SI_TIMER entry is already queue just increment
                  * the overrun count.  Other uses should not try to
                  * send the signal multiple times.
                  */
                 BUG_ON(q->info.si_code != SI_TIMER);
                 q->info.si_overrun++;
                 goto out;
         } 
         /*
          * Deliver the signal to listening signalfds. This must be called
          * with the sighand lock held.
          */
         signalfd_notify(p, sig);
 
         /*
          * Put this signal on the shared-pending queue.
          * We always use the shared queue for process-wide signals,
          * to avoid several races.
          */
         list_add_tail(&q->list, &p->signal->shared_pending.list);
         sigaddset(&p->signal->shared_pending.signal, sig);
 
         __group_complete_signal(sig, p);
 out:
         spin_unlock_irqrestore(&p->sighand->siglock, flags);
         read_unlock(&tasklist_lock);
         return ret;
 }
 
 /*
  * Wake up any threads in the parent blocked in wait* syscalls.
  */
 static inline void __wake_up_parent(struct task_struct *p,
                                     struct task_struct *parent)
 {
         wake_up_interruptible_sync(&parent->signal->wait_chldexit);
 }
 
 /*
  * Let a parent know about the death of a child.
  * For a stopped/continued status change, use do_notify_parent_cldstop instead.
  */
 
 void do_notify_parent(struct task_struct *tsk, int sig)
 {
         struct siginfo info;
         unsigned long flags;
         struct sighand_struct *psig;
 
         BUG_ON(sig == -1);
 
         /* do_notify_parent_cldstop should have been called instead.  */
         BUG_ON(task_is_stopped_or_traced(tsk));
 
         BUG_ON(!tsk->ptrace &&
                (tsk->group_leader != tsk || !thread_group_empty(tsk)));
 
         info.si_signo = sig;
         info.si_errno = 0;
         /*
          * we are under tasklist_lock here so our parent is tied to
          * us and cannot exit and release its namespace.
          *
          * the only it can is to switch its nsproxy with sys_unshare,
          * bu uncharing pid namespaces is not allowed, so we'll always
          * see relevant namespace
          *
          * write_lock() currently calls preempt_disable() which is the
          * same as rcu_read_lock(), but according to Oleg, this is not
          * correct to rely on this
          */
         rcu_read_lock();
         info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
         rcu_read_unlock();
 
         info.si_uid = tsk->uid;
 
         /* FIXME: find out whether or not this is supposed to be c*time. */
         info.si_utime = cputime_to_jiffies(cputime_add(tsk->utime,
                                                        tsk->signal->utime));
         info.si_stime = cputime_to_jiffies(cputime_add(tsk->stime,
                                                        tsk->signal->stime));
 
         info.si_status = tsk->exit_code & 0x7f;
         if (tsk->exit_code & 0x80)
                 info.si_code = CLD_DUMPED;
         else if (tsk->exit_code & 0x7f)
                 info.si_code = CLD_KILLED;
         else {
                 info.si_code = CLD_EXITED;
                 info.si_status = tsk->exit_code >> 8;
         }
 
         psig = tsk->parent->sighand;
         spin_lock_irqsave(&psig->siglock, flags);
         if (!tsk->ptrace && sig == SIGCHLD &&
             (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
              (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
                 /*
                  * We are exiting and our parent doesn't care.  POSIX.1
                  * defines special semantics for setting SIGCHLD to SIG_IGN
                  * or setting the SA_NOCLDWAIT flag: we should be reaped
                  * automatically and not left for our parent's wait4 call.
                  * Rather than having the parent do it as a magic kind of
                  * signal handler, we just set this to tell do_exit that we
                  * can be cleaned up without becoming a zombie.  Note that
                  * we still call __wake_up_parent in this case, because a
                  * blocked sys_wait4 might now return -ECHILD.
                  *
                  * Whether we send SIGCHLD or not for SA_NOCLDWAIT
                  * is implementation-defined: we do (if you don't want
                  * it, just use SIG_IGN instead).
                  */
                 tsk->exit_signal = -1;
                 if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
                         sig = 0;
         }
         if (valid_signal(sig) && sig > 0)
                 __group_send_sig_info(sig, &info, tsk->parent);
         __wake_up_parent(tsk, tsk->parent);
         spin_unlock_irqrestore(&psig->siglock, flags);
 }
 
 static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
 {
         struct siginfo info;
         unsigned long flags;
         struct task_struct *parent;
         struct sighand_struct *sighand;
 
         if (tsk->ptrace & PT_PTRACED)
                 parent = tsk->parent;
         else {
                 tsk = tsk->group_leader;
                 parent = tsk->real_parent;
         }
 
         info.si_signo = SIGCHLD;
         info.si_errno = 0;
         /*
          * see comment in do_notify_parent() abot the following 3 lines
          */
         rcu_read_lock();
         info.si_pid = task_pid_nr_ns(tsk, tsk->parent->nsproxy->pid_ns);
         rcu_read_unlock();
 
         info.si_uid = tsk->uid;
 
         /* FIXME: find out whether or not this is supposed to be c*time. */
         info.si_utime = cputime_to_jiffies(tsk->utime);
         info.si_stime = cputime_to_jiffies(tsk->stime);
 
         info.si_code = why;
         switch (why) {
         case CLD_CONTINUED:
                 info.si_status = SIGCONT;
                 break;
         case CLD_STOPPED:
                 info.si_status = tsk->signal->group_exit_code & 0x7f;
                 break;
         case CLD_TRAPPED:
                 info.si_status = tsk->exit_code & 0x7f;
                 break;
         default:
                 BUG();
         }
 
         sighand = parent->sighand;
         spin_lock_irqsave(&sighand->siglock, flags);
         if (sighand->action[SIGCHLD-1].sa.sa_handler != SIG_IGN &&
             !(sighand->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDSTOP))
                 __group_send_sig_info(SIGCHLD, &info, parent);
         /*
          * Even if SIGCHLD is not generated, we must wake up wait4 calls.
          */
         __wake_up_parent(tsk, parent);
         spin_unlock_irqrestore(&sighand->siglock, flags);
 }
 
 static inline int may_ptrace_stop(void)
 {
         if (!likely(current->ptrace & PT_PTRACED))
                 return 0;
         /*
          * Are we in the middle of do_coredump?
          * If so and our tracer is also part of the coredump stopping
          * is a deadlock situation, and pointless because our tracer
          * is dead so don't allow us to stop.
          * If SIGKILL was already sent before the caller unlocked
          * ->siglock we must see ->core_waiters != 0. Otherwise it
          * is safe to enter schedule().
          */
         if (unlikely(current->mm->core_waiters) &&
             unlikely(current->mm == current->parent->mm))
                 return 0;
 
         return 1;
 }
 
 /*
  * Return nonzero if there is a SIGKILL that should be waking us up.
  * Called with the siglock held.
  */
 static int sigkill_pending(struct task_struct *tsk)
 {
         return ((sigismember(&tsk->pending.signal, SIGKILL) ||
                  sigismember(&tsk->signal->shared_pending.signal, SIGKILL)) &&
                 !unlikely(sigismember(&tsk->blocked, SIGKILL)));
 }
 
 /*
  * This must be called with current->sighand->siglock held.
  *
  * This should be the path for all ptrace stops.
  * We always set current->last_siginfo while stopped here.
  * That makes it a way to test a stopped process for
  * being ptrace-stopped vs being job-control-stopped.
  *
  * If we actually decide not to stop at all because the tracer
  * is gone, we keep current->exit_code unless clear_code.
  */
 static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
 {
         int killed = 0;
 
         if (arch_ptrace_stop_needed(exit_code, info)) {
                 /*
                  * The arch code has something special to do before a
                  * ptrace stop.  This is allowed to block, e.g. for faults
                  * on user stack pages.  We can't keep the siglock while
                  * calling arch_ptrace_stop, so we must release it now.
                  * To preserve proper semantics, we must do this before
                  * any signal bookkeeping like checking group_stop_count.
                  * Meanwhile, a SIGKILL could come in before we retake the
                  * siglock.  That must prevent us from sleeping in TASK_TRACED.
                  * So after regaining the lock, we must check for SIGKILL.
                  */
                 spin_unlock_irq(&current->sighand->siglock);
                 arch_ptrace_stop(exit_code, info);
                 spin_lock_irq(&current->sighand->siglock);
                 killed = sigkill_pending(current);
         }
 
         /*
          * If there is a group stop in progress,
          * we must participate in the bookkeeping.
          */
         if (current->signal->group_stop_count > 0)
                 --current->signal->group_stop_count;
 
         current->last_siginfo = info;
         current->exit_code = exit_code;
 
         /* Let the debugger run.  */
         __set_current_state(TASK_TRACED);
         spin_unlock_irq(&current->sighand->siglock);
         read_lock(&tasklist_lock);
         if (!unlikely(killed) && may_ptrace_stop()) {
                 do_notify_parent_cldstop(current, CLD_TRAPPED);
                 read_unlock(&tasklist_lock);
                 current->flags &= ~PF_NOSCHED;
                 schedule();
         } else {
                 /*
                  * By the time we got the lock, our tracer went away.
                  * Don't drop the lock yet, another tracer may come.
                  */
                 __set_current_state(TASK_RUNNING);
                 if (clear_code)
                         current->exit_code = 0;
                 read_unlock(&tasklist_lock);
         }
 
         /*
          * While in TASK_TRACED, we were considered "frozen enough".
          * Now that we woke up, it's crucial if we're supposed to be
          * frozen that we freeze now before running anything substantial.
          */
         try_to_freeze();
 
         /*
          * We are back.  Now reacquire the siglock before touching
          * last_siginfo, so that we are sure to have synchronized with
          * any signal-sending on another CPU that wants to examine it.
          */
         spin_lock_irq(&current->sighand->siglock);
         current->last_siginfo = NULL;
 
         /*
          * Queued signals ignored us while we were stopped for tracing.
          * So check for any that we should take before resuming user mode.
          * This sets TIF_SIGPENDING, but never clears it.
          */
         recalc_sigpending_tsk(current);
 }
 
 void ptrace_notify(int exit_code)
 {
         siginfo_t info;
 
         BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
 
         memset(&info, 0, sizeof info);
         info.si_signo = SIGTRAP;
         info.si_code = exit_code;
         info.si_pid = task_pid_vnr(current);
         info.si_uid = current->uid;
 
         /* Let the debugger run.  */
         spin_lock_irq(&current->sighand->siglock);
         ptrace_stop(exit_code, 1, &info);
         spin_unlock_irq(&current->sighand->siglock);
 }
 
 static void
 finish_stop(int stop_count)
 {
         /*
          * If there are no other threads in the group, or if there is
          * a group stop in progress and we are the last to stop,
          * report to the parent.  When ptraced, every thread reports itself.
          */
         if (stop_count == 0 || (current->ptrace & PT_PTRACED)) {
                 read_lock(&tasklist_lock);
                 do_notify_parent_cldstop(current, CLD_STOPPED);
                 read_unlock(&tasklist_lock);
         }
 
         do {
                 current->flags &= ~PF_NOSCHED;
                 schedule();
         } while (try_to_freeze());
         /*
          * Now we don't run again until continued.
          */
         current->exit_code = 0;
 }
 
 /*
  * This performs the stopping for SIGSTOP and other stop signals.
  * We have to stop all threads in the thread group.
  * Returns nonzero if we've actually stopped and released the siglock.
  * Returns zero if we didn't stop and still hold the siglock.
  */
 static int do_signal_stop(int signr)
 {
         struct signal_struct *sig = current->signal;
         int stop_count;
 
         if (sig->group_stop_count > 0) {
                 /*
                  * There is a group stop in progress.  We don't need to
                  * start another one.
                  */
                 stop_count = --sig->group_stop_count;
         } else {
                 struct task_struct *t;
 
                 if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
                     unlikely(sig->group_exit_task))
                         return 0;
                 /*
                  * There is no group stop already in progress.
                  * We must initiate one now.
                  */
                 sig->group_exit_code = signr;
 
                 stop_count = 0;
                 for (t = next_thread(current); t != current; t = next_thread(t))
                         /*
                          * Setting state to TASK_STOPPED for a group
                          * stop is always done with the siglock held,
                          * so this check has no races.
                          */
                         if (!(t->flags & PF_EXITING) &&
                             !task_is_stopped_or_traced(t)) {
                                 stop_count++;
                                 signal_wake_up(t, 0);
                         }
                 sig->group_stop_count = stop_count;
         }
 
         if (stop_count == 0)
                 sig->flags = SIGNAL_STOP_STOPPED;
         current->exit_code = sig->group_exit_code;
         __set_current_state(TASK_STOPPED);
 
         spin_unlock_irq(&current->sighand->siglock);
         finish_stop(stop_count);
         return 1;
 }
 
 int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
                           struct pt_regs *regs, void *cookie)
 {
         sigset_t *mask = &current->blocked;
         int signr = 0;
 
 relock:
         /*
          * We'll jump back here after any time we were stopped in TASK_STOPPED.
          * While in TASK_STOPPED, we were considered "frozen enough".
          * Now that we woke up, it's crucial if we're supposed to be
          * frozen that we freeze now before running anything substantial.
          */
         try_to_freeze();
 
 #ifdef CONFIG_PREEMPT_RT
         might_sleep();
 #endif
         spin_lock_irq(&current->sighand->siglock);
         for (;;) {
                 struct k_sigaction *ka;
 
                 if (unlikely(current->signal->group_stop_count > 0) &&
                     do_signal_stop(0))
                         goto relock;
 
                 signr = dequeue_signal(current, mask, info);
 
                 if (!signr)
                         break; /* will return 0 */
 
                 if ((current->ptrace & PT_PTRACED) && signr != SIGKILL) {
                         ptrace_signal_deliver(regs, cookie);
 
                         /* Let the debugger run.  */
                         ptrace_stop(signr, 0, info);
 
                         /* We're back.  Did the debugger cancel the sig?  */
                         signr = current->exit_code;
                         if (signr == 0)
                                 continue;
 
                         current->exit_code = 0;
 
                         /* Update the siginfo structure if the signal has
                            changed.  If the debugger wanted something
                            specific in the siginfo structure then it should
                            have updated *info via PTRACE_SETSIGINFO.  */
                         if (signr != info->si_signo) {
                                 info->si_signo = signr;
                                 info->si_errno = 0;
                                 info->si_code = SI_USER;
                                 info->si_pid = task_pid_vnr(current->parent);
                                 info->si_uid = current->parent->uid;
                         }
 
                         /* If the (new) signal is now blocked, requeue it.  */
                         if (sigismember(&current->blocked, signr)) {
                                 specific_send_sig_info(signr, info, current);
                                 continue;
                         }
                 }
 
                 ka = &current->sighand->action[signr-1];
                 if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
                         continue;
                 if (ka->sa.sa_handler != SIG_DFL) {
                         /* Run the handler.  */
                         *return_ka = *ka;
 
                         if (ka->sa.sa_flags & SA_ONESHOT)
                                 ka->sa.sa_handler = SIG_DFL;
 
                         break; /* will return non-zero "signr" value */
                 }
 
                 /*
                  * Now we are doing the default action for this signal.
                  */
                 if (sig_kernel_ignore(signr)) /* Default is nothing. */
                         continue;
 
                 /*
                  * Global init gets no signals it doesn't want.
                  */
                 if (is_global_init(current))
                         continue;
 
                 if (sig_kernel_stop(signr)) {
                         /*
                          * The default action is to stop all threads in
                          * the thread group.  The job control signals
                          * do nothing in an orphaned pgrp, but SIGSTOP
                          * always works.  Note that siglock needs to be
                          * dropped during the call to is_orphaned_pgrp()
                          * because of lock ordering with tasklist_lock.
                          * This allows an intervening SIGCONT to be posted.
                          * We need to check for that and bail out if necessary.
                          */
                         if (signr != SIGSTOP) {
                                 spin_unlock_irq(&current->sighand->siglock);
 
                                 /* signals can be posted during this window */
 
                                 if (is_current_pgrp_orphaned())
                                         goto relock;
 
                                 spin_lock_irq(&current->sighand->siglock);
                         }
 
                         if (likely(do_signal_stop(signr))) {
                                 /* It released the siglock.  */
                                 goto relock;
                         }
 
                         /*
                          * We didn't actually stop, due to a race
                          * with SIGCONT or something like that.
                          */
                         continue;
                 }
 
                 spin_unlock_irq(&current->sighand->siglock);
 
                 /*
                  * Anything else is fatal, maybe with a core dump.
                  */
                 current->flags |= PF_SIGNALED;
                 if ((signr != SIGKILL) && print_fatal_signals)
                         print_fatal_signal(regs, signr);
                 if (sig_kernel_coredump(signr)) {
                         /*
                          * If it was able to dump core, this kills all
                          * other threads in the group and synchronizes with
                          * their demise.  If we lost the race with another
                          * thread getting here, it set group_exit_code
                          * first and our do_group_exit call below will use
                          * that value and ignore the one we pass it.
                          */
                         do_coredump((long)signr, signr, regs);
                 }
 
                 /*
                  * Death signals, no core dump.
                  */
                 do_group_exit(signr);
                 /* NOTREACHED */
         }
         spin_unlock_irq(&current->sighand->siglock);
         return signr;
 }
 
 void exit_signals(struct task_struct *tsk)
 {
         int group_stop = 0;
         struct task_struct *t;
 
         if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
                 tsk->flags |= PF_EXITING;
                 return;
         }
 
         spin_lock_irq(&tsk->sighand->siglock);
         /*
          * From now this task is not visible for group-wide signals,
          * see wants_signal(), do_signal_stop().
          */
         tsk->flags |= PF_EXITING;
         if (!signal_pending(tsk))
                 goto out;
 
         /* It could be that __group_complete_signal() choose us to
          * notify about group-wide signal. Another thread should be
          * woken now to take the signal since we will not.
          */
         for (t = tsk; (t = next_thread(t)) != tsk; )
                 if (!signal_pending(t) && !(t->flags & PF_EXITING))
                         recalc_sigpending_and_wake(t);
 
         if (unlikely(tsk->signal->group_stop_count) &&
                         !--tsk->signal->group_stop_count) {
                 tsk->signal->flags = SIGNAL_STOP_STOPPED;
                 group_stop = 1;
         }
 out:
         spin_unlock_irq(&tsk->sighand->siglock);
 
         if (unlikely(group_stop)) {
                 read_lock(&tasklist_lock);
                 do_notify_parent_cldstop(tsk, CLD_STOPPED);
                 read_unlock(&tasklist_lock);
         }
 }
 
 EXPORT_SYMBOL(recalc_sigpending);
 EXPORT_SYMBOL_GPL(dequeue_signal);
 EXPORT_SYMBOL(flush_signals);
 EXPORT_SYMBOL(force_sig);
 EXPORT_SYMBOL(kill_proc);
 EXPORT_SYMBOL(ptrace_notify);
 EXPORT_SYMBOL(send_sig);
 EXPORT_SYMBOL(send_sig_info);
 EXPORT_SYMBOL(sigprocmask);
 EXPORT_SYMBOL(block_all_signals);
 EXPORT_SYMBOL(unblock_all_signals);
 
 
 /*
  * System call entry points.
  */
 
 asmlinkage long sys_restart_syscall(void)
 {
         struct restart_block *restart = &current_thread_info()->restart_block;
         return restart->fn(restart);
 }
 
 long do_no_restart_syscall(struct restart_block *param)
 {
         return -EINTR;
 }
 
 /*
  * We don't need to get the kernel lock - this is all local to this
  * particular thread.. (and that's good, because this is _heavily_
  * used by various programs)
  */
 
 /*
  * This is also useful for kernel threads that want to temporarily
  * (or permanently) block certain signals.
  *
  * NOTE! Unlike the user-mode sys_sigprocmask(), the kernel
  * interface happily blocks "unblockable" signals like SIGKILL
  * and friends.
  */
 int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
 {
         int error;
 
         spin_lock_irq(&current->sighand->siglock);
         if (oldset)
                 *oldset = current->blocked;
 
         error = 0;
         switch (how) {
         case SIG_BLOCK:
                 sigorsets(&current->blocked, &current->blocked, set);
                 break;
         case SIG_UNBLOCK:
                 signandsets(&current->blocked, &current->blocked, set);
                 break;
         case SIG_SETMASK:
                 current->blocked = *set;
                 break;
         default:
                 error = -EINVAL;
         }
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
         return error;
 }
 
 asmlinkage long
 sys_rt_sigprocmask(int how, sigset_t __user *set, sigset_t __user *oset, size_t sigsetsize)
 {
         int error = -EINVAL;
         sigset_t old_set, new_set;
 
         /* XXX: Don't preclude handling different sized sigset_t's.  */
         if (sigsetsize != sizeof(sigset_t))
                 goto out;
 
         if (set) {
                 error = -EFAULT;
                 if (copy_from_user(&new_set, set, sizeof(*set)))
                         goto out;
                 sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
 
                 error = sigprocmask(how, &new_set, &old_set);
                 if (error)
                         goto out;
                 if (oset)
                         goto set_old;
         } else if (oset) {
                 spin_lock_irq(&current->sighand->siglock);
                 old_set = current->blocked;
                 spin_unlock_irq(&current->sighand->siglock);
 
         set_old:
                 error = -EFAULT;
                 if (copy_to_user(oset, &old_set, sizeof(*oset)))
                         goto out;
         }
         error = 0;
 out:
         return error;
 }
 
 long do_sigpending(void __user *set, unsigned long sigsetsize)
 {
         long error = -EINVAL;
         sigset_t pending;
 
         if (sigsetsize > sizeof(sigset_t))
                 goto out;
 
         spin_lock_irq(&current->sighand->siglock);
         sigorsets(&pending, &current->pending.signal,
                   &current->signal->shared_pending.signal);
         spin_unlock_irq(&current->sighand->siglock);
 
         /* Outside the lock because only this thread touches it.  */
         sigandsets(&pending, &current->blocked, &pending);
 
         error = -EFAULT;
         if (!copy_to_user(set, &pending, sigsetsize))
                 error = 0;
 
 out:
         return error;
 }       
 
 asmlinkage long
 sys_rt_sigpending(sigset_t __user *set, size_t sigsetsize)
 {
         return do_sigpending(set, sigsetsize);
 }
 
 #ifndef HAVE_ARCH_COPY_SIGINFO_TO_USER
 
 int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
 {
         int err;
 
         if (!access_ok (VERIFY_WRITE, to, sizeof(siginfo_t)))
                 return -EFAULT;
         if (from->si_code < 0)
                 return __copy_to_user(to, from, sizeof(siginfo_t))
                         ? -EFAULT : 0;
         /*
          * If you change siginfo_t structure, please be sure
          * this code is fixed accordingly.
          * Please remember to update the signalfd_copyinfo() function
          * inside fs/signalfd.c too, in case siginfo_t changes.
          * It should never copy any pad contained in the structure
          * to avoid security leaks, but must copy the generic
          * 3 ints plus the relevant union member.
          */
         err = __put_user(from->si_signo, &to->si_signo);
         err |= __put_user(from->si_errno, &to->si_errno);
         err |= __put_user((short)from->si_code, &to->si_code);
         switch (from->si_code & __SI_MASK) {
         case __SI_KILL:
                 err |= __put_user(from->si_pid, &to->si_pid);
                 err |= __put_user(from->si_uid, &to->si_uid);
                 break;
         case __SI_TIMER:
                  err |= __put_user(from->si_tid, &to->si_tid);
                  err |= __put_user(from->si_overrun, &to->si_overrun);
                  err |= __put_user(from->si_ptr, &to->si_ptr);
                 break;
         case __SI_POLL:
                 err |= __put_user(from->si_band, &to->si_band);
                 err |= __put_user(from->si_fd, &to->si_fd);
                 break;
         case __SI_FAULT:
                 err |= __put_user(from->si_addr, &to->si_addr);
 #ifdef __ARCH_SI_TRAPNO
                 err |= __put_user(from->si_trapno, &to->si_trapno);
 #endif
                 break;
         case __SI_CHLD:
                 err |= __put_user(from->si_pid, &to->si_pid);
                 err |= __put_user(from->si_uid, &to->si_uid);
                 err |= __put_user(from->si_status, &to->si_status);
                 err |= __put_user(from->si_utime, &to->si_utime);
                 err |= __put_user(from->si_stime, &to->si_stime);
                 break;
         case __SI_RT: /* This is not generated by the kernel as of now. */
         case __SI_MESGQ: /* But this is */
                 err |= __put_user(from->si_pid, &to->si_pid);
                 err |= __put_user(from->si_uid, &to->si_uid);
                 err |= __put_user(from->si_ptr, &to->si_ptr);
                 break;
         default: /* this is just in case for now ... */
                 err |= __put_user(from->si_pid, &to->si_pid);
                 err |= __put_user(from->si_uid, &to->si_uid);
                 break;
         }
         return err;
 }
 
 #endif
 
 asmlinkage long
 sys_rt_sigtimedwait(const sigset_t __user *uthese,
                     siginfo_t __user *uinfo,
                     const struct timespec __user *uts,
                     size_t sigsetsize)
 {
         int ret, sig;
         sigset_t these;
         struct timespec ts;
         siginfo_t info;
         long timeout = 0;
 
         /* XXX: Don't preclude handling different sized sigset_t's.  */
         if (sigsetsize != sizeof(sigset_t))
                 return -EINVAL;
 
         if (copy_from_user(&these, uthese, sizeof(these)))
                 return -EFAULT;
                 
         /*
          * Invert the set of allowed signals to get those we
          * want to block.
          */
         sigdelsetmask(&these, sigmask(SIGKILL)|sigmask(SIGSTOP));
         signotset(&these);
 
         if (uts) {
                 if (copy_from_user(&ts, uts, sizeof(ts)))
                         return -EFAULT;
                 if (ts.tv_nsec >= 1000000000L || ts.tv_nsec < 0
                     || ts.tv_sec < 0)
                         return -EINVAL;
         }
 
         spin_lock_irq(&current->sighand->siglock);
         sig = dequeue_signal(current, &these, &info);
         if (!sig) {
                 timeout = MAX_SCHEDULE_TIMEOUT;
                 if (uts)
                         timeout = (timespec_to_jiffies(&ts)
                                    + (ts.tv_sec || ts.tv_nsec));
 
                 if (timeout) {
                         /* None ready -- temporarily unblock those we're
                          * interested while we are sleeping in so that we'll
                          * be awakened when they arrive.  */
                         current->real_blocked = current->blocked;
                         sigandsets(&current->blocked, &current->blocked, &these);
                         recalc_sigpending();
                         spin_unlock_irq(&current->sighand->siglock);
 
                         timeout = schedule_timeout_interruptible(timeout);
 
                         spin_lock_irq(&current->sighand->siglock);
                         sig = dequeue_signal(current, &these, &info);
                         current->blocked = current->real_blocked;
                         siginitset(&current->real_blocked, 0);
                         recalc_sigpending();
                 }
         }
         spin_unlock_irq(&current->sighand->siglock);
 
         if (sig) {
                 ret = sig;
                 if (uinfo) {
                         if (copy_siginfo_to_user(uinfo, &info))
                                 ret = -EFAULT;
                 }
         } else {
                 ret = -EAGAIN;
                 if (timeout)
                         ret = -EINTR;
         }
 
         return ret;
 }
 
 asmlinkage long
 sys_kill(int pid, int sig)
 {
         struct siginfo info;
 
         info.si_signo = sig;
         info.si_errno = 0;
         info.si_code = SI_USER;
         info.si_pid = task_tgid_vnr(current);
         info.si_uid = current->uid;
 
         return kill_something_info(sig, &info, pid);
 }
 
 static int do_tkill(int tgid, int pid, int sig)
 {
         int error;
         struct siginfo info;
         struct task_struct *p;
 
         error = -ESRCH;
         info.si_signo = sig;
         info.si_errno = 0;
         info.si_code = SI_TKILL;
         info.si_pid = task_tgid_vnr(current);
         info.si_uid = current->uid;
 
         read_lock(&tasklist_lock);
         p = find_task_by_vpid(pid);
         if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
                 error = check_kill_permission(sig, &info, p);
                 /*
                  * The null signal is a permissions and process existence
                  * probe.  No signal is actually delivered.
                  */
                 if (!error && sig && p->sighand) {
                         spin_lock_irq(&p->sighand->siglock);
                         handle_stop_signal(sig, p);
                         error = specific_send_sig_info(sig, &info, p);
                         spin_unlock_irq(&p->sighand->siglock);
                 }
         }
         read_unlock(&tasklist_lock);
 
         return error;
 }
 
 /**
  *  sys_tgkill - send signal to one specific thread
  *  @tgid: the thread group ID of the thread
  *  @pid: the PID of the thread
  *  @sig: signal to be sent
  *
  *  This syscall also checks the @tgid and returns -ESRCH even if the PID
  *  exists but it's not belonging to the target process anymore. This
  *  method solves the problem of threads exiting and PIDs getting reused.
  */
 asmlinkage long sys_tgkill(int tgid, int pid, int sig)
 {
         /* This is only valid for single tasks */
         if (pid <= 0 || tgid <= 0)
                 return -EINVAL;
 
         return do_tkill(tgid, pid, sig);
 }
 
 /*
  *  Send a signal to only one task, even if it's a CLONE_THREAD task.
  */
 asmlinkage long
 sys_tkill(int pid, int sig)
 {
         /* This is only valid for single tasks */
         if (pid <= 0)
                 return -EINVAL;
 
         return do_tkill(0, pid, sig);
 }
 
 asmlinkage long
 sys_rt_sigqueueinfo(int pid, int sig, siginfo_t __user *uinfo)
 {
         siginfo_t info;
 
         if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
                 return -EFAULT;
 
         /* Not even root can pretend to send signals from the kernel.
            Nor can they impersonate a kill(), which adds source info.  */
         if (info.si_code >= 0)
                 return -EPERM;
         info.si_signo = sig;
 
         /* POSIX.1b doesn't mention process groups.  */
         return kill_proc_info(sig, &info, pid);
 }
 
 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 {
         struct k_sigaction *k;
         sigset_t mask;
 
         if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
                 return -EINVAL;
 
         k = &current->sighand->action[sig-1];
 
         spin_lock_irq(&current->sighand->siglock);
         if (oact)
                 *oact = *k;
 
         if (act) {
                 sigdelsetmask(&act->sa.sa_mask,
                               sigmask(SIGKILL) | sigmask(SIGSTOP));
                 *k = *act;
                 /*
                  * POSIX 3.3.1.3:
                  *  "Setting a signal action to SIG_IGN for a signal that is
                  *   pending shall cause the pending signal to be discarded,
                  *   whether or not it is blocked."
                  *
                  *  "Setting a signal action to SIG_DFL for a signal that is
                  *   pending and whose default action is to ignore the signal
                  *   (for example, SIGCHLD), shall cause the pending signal to
                  *   be discarded, whether or not it is blocked"
                  */
                 if (act->sa.sa_handler == SIG_IGN ||
                    (act->sa.sa_handler == SIG_DFL && sig_kernel_ignore(sig))) {
                         struct task_struct *t = current;
                         sigemptyset(&mask);
                         sigaddset(&mask, sig);
                         rm_from_queue_full(&mask, &t->signal->shared_pending);
                         do {
                                 rm_from_queue_full(&mask, &t->pending);
                                 t = next_thread(t);
                         } while (t != current);
                 }
         }
 
         spin_unlock_irq(&current->sighand->siglock);
         return 0;
 }
 
 int 
 do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp)
 {
         stack_t oss;
         int error;
 
         if (uoss) {
                 oss.ss_sp = (void __user *) current->sas_ss_sp;
                 oss.ss_size = current->sas_ss_size;
                 oss.ss_flags = sas_ss_flags(sp);
         }
 
         if (uss) {
                 void __user *ss_sp;
                 size_t ss_size;
                 int ss_flags;
 
                 error = -EFAULT;
                 if (!access_ok(VERIFY_READ, uss, sizeof(*uss))
                     || __get_user(ss_sp, &uss->ss_sp)
                     || __get_user(ss_flags, &uss->ss_flags)
                     || __get_user(ss_size, &uss->ss_size))
                         goto out;
 
                 error = -EPERM;
                 if (on_sig_stack(sp))
                         goto out;
 
                 error = -EINVAL;
                 /*
                  *
                  * Note - this code used to test ss_flags incorrectly
                  *        old code may have been written using ss_flags==0
                  *        to mean ss_flags==SS_ONSTACK (as this was the only
                  *        way that worked) - this fix preserves that older
                  *        mechanism
                  */
                 if (ss_flags != SS_DISABLE && ss_flags != SS_ONSTACK && ss_flags != 0)
                         goto out;
 
                 if (ss_flags == SS_DISABLE) {
                         ss_size = 0;
                         ss_sp = NULL;
                 } else {
                         error = -ENOMEM;
                         if (ss_size < MINSIGSTKSZ)
                                 goto out;
                 }
 
                 current->sas_ss_sp = (unsigned long) ss_sp;
                 current->sas_ss_size = ss_size;
         }
 
         if (uoss) {
                 error = -EFAULT;
                 if (copy_to_user(uoss, &oss, sizeof(oss)))
                         goto out;
         }
 
         error = 0;
 out:
         return error;
 }
 
 #ifdef __ARCH_WANT_SYS_SIGPENDING
 
 asmlinkage long
 sys_sigpending(old_sigset_t __user *set)
 {
         return do_sigpending(set, sizeof(*set));
 }
 
 #endif
 
 #ifdef __ARCH_WANT_SYS_SIGPROCMASK
 /* Some platforms have their own version with special arguments others
    support only sys_rt_sigprocmask.  */
 
 asmlinkage long
 sys_sigprocmask(int how, old_sigset_t __user *set, old_sigset_t __user *oset)
 {
         int error;
         old_sigset_t old_set, new_set;
 
         if (set) {
                 error = -EFAULT;
                 if (copy_from_user(&new_set, set, sizeof(*set)))
                         goto out;
                 new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP));
 
                 spin_lock_irq(&current->sighand->siglock);
                 old_set = current->blocked.sig[0];
 
                 error = 0;
                 switch (how) {
                 default:
                         error = -EINVAL;
                         break;
                 case SIG_BLOCK:
                         sigaddsetmask(&current->blocked, new_set);
                         break;
                 case SIG_UNBLOCK:
                         sigdelsetmask(&current->blocked, new_set);
                         break;
                 case SIG_SETMASK:
                         current->blocked.sig[0] = new_set;
                         break;
                 }
 
                 recalc_sigpending();
                 spin_unlock_irq(&current->sighand->siglock);
                 if (error)
                         goto out;
                 if (oset)
                         goto set_old;
         } else if (oset) {
                 old_set = current->blocked.sig[0];
         set_old:
                 error = -EFAULT;
                 if (copy_to_user(oset, &old_set, sizeof(*oset)))
                         goto out;
         }
         error = 0;
 out:
         return error;
 }
 #endif /* __ARCH_WANT_SYS_SIGPROCMASK */
 
 #ifdef __ARCH_WANT_SYS_RT_SIGACTION
 asmlinkage long
 sys_rt_sigaction(int sig,
                  const struct sigaction __user *act,
                  struct sigaction __user *oact,
                  size_t sigsetsize)
 {
         struct k_sigaction new_sa, old_sa;
         int ret = -EINVAL;
 
         /* XXX: Don't preclude handling different sized sigset_t's.  */
         if (sigsetsize != sizeof(sigset_t))
                 goto out;
 
         if (act) {
                 if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
                         return -EFAULT;
         }
 
         ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
 
         if (!ret && oact) {
                 if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
                         return -EFAULT;
         }
 out:
         return ret;
 }
 #endif /* __ARCH_WANT_SYS_RT_SIGACTION */
 
 #ifdef __ARCH_WANT_SYS_SGETMASK
 
 /*
  * For backwards compatibility.  Functionality superseded by sigprocmask.
  */
 asmlinkage long
 sys_sgetmask(void)
 {
         /* SMP safe */
         return current->blocked.sig[0];
 }
 
 asmlinkage long
 sys_ssetmask(int newmask)
 {
         int old;
 
         spin_lock_irq(&current->sighand->siglock);
         old = current->blocked.sig[0];
 
         siginitset(&current->blocked, newmask & ~(sigmask(SIGKILL)|
                                                   sigmask(SIGSTOP)));
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
         return old;
 }
 #endif /* __ARCH_WANT_SGETMASK */
 
 #ifdef __ARCH_WANT_SYS_SIGNAL
 /*
  * For backwards compatibility.  Functionality superseded by sigaction.
  */
 asmlinkage unsigned long
 sys_signal(int sig, __sighandler_t handler)
 {
         struct k_sigaction new_sa, old_sa;
         int ret;
 
         new_sa.sa.sa_handler = handler;
         new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
         sigemptyset(&new_sa.sa.sa_mask);
 
         ret = do_sigaction(sig, &new_sa, &old_sa);
 
         return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
 }
 #endif /* __ARCH_WANT_SYS_SIGNAL */
 
 #ifdef __ARCH_WANT_SYS_PAUSE
 
 asmlinkage long
 sys_pause(void)
 {
         current->state = TASK_INTERRUPTIBLE;
         schedule();
         return -ERESTARTNOHAND;
 }
 
 #endif
 
 #ifdef __ARCH_WANT_SYS_RT_SIGSUSPEND
 asmlinkage long sys_rt_sigsuspend(sigset_t __user *unewset, size_t sigsetsize)
 {
         sigset_t newset;
 
         /* XXX: Don't preclude handling different sized sigset_t's.  */
         if (sigsetsize != sizeof(sigset_t))
                 return -EINVAL;
 
         if (copy_from_user(&newset, unewset, sizeof(newset)))
                 return -EFAULT;
         sigdelsetmask(&newset, sigmask(SIGKILL)|sigmask(SIGSTOP));
 
         spin_lock_irq(&current->sighand->siglock);
         current->saved_sigmask = current->blocked;
         current->blocked = newset;
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
         current->state = TASK_INTERRUPTIBLE;
         schedule();
         set_thread_flag(TIF_RESTORE_SIGMASK);
         return -ERESTARTNOHAND;
 }
 #endif /* __ARCH_WANT_SYS_RT_SIGSUSPEND */
 
 __attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma)
 {
         return NULL;
 }
 
 void __init signals_init(void)
 {
         sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
 }