Merge 'Linux v3.0' into Litmus

Some notes:
* Litmus^RT scheduling class is the topmost scheduling class
  (above stop_sched_class).
* scheduler_ipi() function (e.g., in smp_reschedule_interrupt())
  may increase IPI latencies.
* Added path into schedule() to quickly re-evaluate scheduling
  decision without becoming preemptive again. This used to be
  a standard path before the removal of BKL.

Conflicts:
	Makefile
	arch/arm/kernel/calls.S
	arch/arm/kernel/smp.c
	arch/x86/include/asm/unistd_32.h
	arch/x86/kernel/smp.c
	arch/x86/kernel/syscall_table_32.S
	include/linux/hrtimer.h
	kernel/printk.c
	kernel/sched.c
	kernel/sched_fair.c

1 files changed, 612 insertions, 281 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 919562c3d6b7..415d85d6f6c6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -124,7 +124,7 @@ static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
 
 static int recalc_sigpending_tsk(struct task_struct *t)
 {
-        if (t->signal->group_stop_count > 0 ||
+        if ((t->group_stop & GROUP_STOP_PENDING) ||
             PENDING(&t->pending, &t->blocked) ||
             PENDING(&t->signal->shared_pending, &t->blocked)) {
                 set_tsk_thread_flag(t, TIF_SIGPENDING);
@@ -223,10 +223,87 @@ static inline void print_dropped_signal(int sig)
                                 current->comm, current->pid, sig);
 }
 
+/**
+ * task_clear_group_stop_trapping - clear group stop trapping bit
+ * @task: target task
+ *
+ * If GROUP_STOP_TRAPPING is set, a ptracer is waiting for us.  Clear it
+ * and wake up the ptracer.  Note that we don't need any further locking.
+ * @task->siglock guarantees that @task->parent points to the ptracer.
+ *
+ * CONTEXT:
+ * Must be called with @task->sighand->siglock held.
+ */
+static void task_clear_group_stop_trapping(struct task_struct *task)
+{
+        if (unlikely(task->group_stop & GROUP_STOP_TRAPPING)) {
+                task->group_stop &= ~GROUP_STOP_TRAPPING;
+                __wake_up_sync_key(&task->parent->signal->wait_chldexit,
+                                   TASK_UNINTERRUPTIBLE, 1, task);
+        }
+}
+
+/**
+ * task_clear_group_stop_pending - clear pending group stop
+ * @task: target task
+ *
+ * Clear group stop states for @task.
+ *
+ * CONTEXT:
+ * Must be called with @task->sighand->siglock held.
+ */
+void task_clear_group_stop_pending(struct task_struct *task)
+{
+        task->group_stop &= ~(GROUP_STOP_PENDING | GROUP_STOP_CONSUME |
+                              GROUP_STOP_DEQUEUED);
+}
+
+/**
+ * task_participate_group_stop - participate in a group stop
+ * @task: task participating in a group stop
+ *
+ * @task has GROUP_STOP_PENDING set and is participating in a group stop.
+ * Group stop states are cleared and the group stop count is consumed if
+ * %GROUP_STOP_CONSUME was set.  If the consumption completes the group
+ * stop, the appropriate %SIGNAL_* flags are set.
+ *
+ * CONTEXT:
+ * Must be called with @task->sighand->siglock held.
+ *
+ * RETURNS:
+ * %true if group stop completion should be notified to the parent, %false
+ * otherwise.
+ */
+static bool task_participate_group_stop(struct task_struct *task)
+{
+        struct signal_struct *sig = task->signal;
+        bool consume = task->group_stop & GROUP_STOP_CONSUME;
+
+        WARN_ON_ONCE(!(task->group_stop & GROUP_STOP_PENDING));
+
+        task_clear_group_stop_pending(task);
+
+        if (!consume)
+                return false;
+
+        if (!WARN_ON_ONCE(sig->group_stop_count == 0))
+                sig->group_stop_count--;
+
+        /*
+         * Tell the caller to notify completion iff we are entering into a
+         * fresh group stop.  Read comment in do_signal_stop() for details.
+         */
+        if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
+                sig->flags = SIGNAL_STOP_STOPPED;
+                return true;
+        }
+        return false;
+}
+
 /*
  * allocate a new signal queue record
  * - this may be called without locks if and only if t == current, otherwise an
- *   appopriate lock must be held to stop the target task from exiting
+ *   appropriate lock must be held to stop the target task from exiting
  */
 static struct sigqueue *
 __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimit)
@@ -375,15 +452,15 @@ int unhandled_signal(struct task_struct *tsk, int sig)
         return !tracehook_consider_fatal_signal(tsk, sig);
 }
 
-
-/* Notify the system that a driver wants to block all signals for this
+/*
+ * 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.  */
-
+ * 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)
 {
@@ -434,9 +511,10 @@ still_pending:
                 copy_siginfo(info, &first->info);
                 __sigqueue_free(first);
         } 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.
+                /*
+                 * 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.
                  */
                 info->si_signo = sig;
                 info->si_errno = 0;
@@ -468,7 +546,7 @@ static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
 }
 
 /*
- * Dequeue a signal and return the element to the caller, which is 
+ * Dequeue a signal and return the element to the caller, which is
  * expected to free it.
  *
  * All callers have to hold the siglock.
@@ -490,7 +568,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
                  * 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
+                 * 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
@@ -526,7 +604,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
                  * is to alert stop-signal processing code when another
                  * processor has come along and cleared the flag.
                  */
-                tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
+                current->group_stop |= GROUP_STOP_DEQUEUED;
         }
         if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) {
                 /*
@@ -591,7 +669,7 @@ static int rm_from_queue_full(sigset_t *mask, struct sigpending *s)
         if (sigisemptyset(&m))
                 return 0;
 
-        signandsets(&s->signal, &s->signal, mask);
+        sigandnsets(&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);
@@ -636,13 +714,33 @@ static inline bool si_fromuser(const struct siginfo *info)
 }
 
 /*
+ * called with RCU read lock from check_kill_permission()
+ */
+static int kill_ok_by_cred(struct task_struct *t)
+{
+        const struct cred *cred = current_cred();
+        const struct cred *tcred = __task_cred(t);
+
+        if (cred->user->user_ns == tcred->user->user_ns &&
+            (cred->euid == tcred->suid ||
+             cred->euid == tcred->uid ||
+             cred->uid  == tcred->suid ||
+             cred->uid  == tcred->uid))
+                return 1;
+
+        if (ns_capable(tcred->user->user_ns, CAP_KILL))
+                return 1;
+
+        return 0;
+}
+
+/*
  * Bad permissions for sending the signal
  * - the caller must hold the RCU read lock
  */
 static int check_kill_permission(int sig, struct siginfo *info,
                                  struct task_struct *t)
 {
-        const struct cred *cred, *tcred;
         struct pid *sid;
         int error;
 
@@ -656,14 +754,8 @@ static int check_kill_permission(int sig, struct siginfo *info,
         if (error)
                 return error;
 
-        cred = current_cred();
-        tcred = __task_cred(t);
         if (!same_thread_group(current, t) &&
-            (cred->euid ^ tcred->suid) &&
-            (cred->euid ^ tcred->uid) &&
-            (cred->uid  ^ tcred->suid) &&
-            (cred->uid  ^ tcred->uid) &&
-            !capable(CAP_KILL)) {
+            !kill_ok_by_cred(t)) {
                 switch (sig) {
                 case SIGCONT:
                         sid = task_session(t);
@@ -712,34 +804,14 @@ static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
         } else if (sig == SIGCONT) {
                 unsigned int why;
                 /*
-                 * Remove all stop signals from all queues,
-                 * and wake all threads.
+                 * Remove all stop signals from all queues, wake all threads.
                  */
                 rm_from_queue(SIG_KERNEL_STOP_MASK, &signal->shared_pending);
                 t = p;
                 do {
-                        unsigned int state;
+                        task_clear_group_stop_pending(t);
                         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);
+                        wake_up_state(t, __TASK_STOPPED);
                 } while_each_thread(p, t);
 
                 /*
@@ -765,13 +837,6 @@ static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
                         signal->flags = why | SIGNAL_STOP_CONTINUED;
                         signal->group_stop_count = 0;
                         signal->group_exit_code = 0;
-                } 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.
-                         */
-                        signal->flags &= ~SIGNAL_STOP_DEQUEUED;
                 }
         }
 
@@ -860,6 +925,7 @@ static void complete_signal(int sig, struct task_struct *p, int group)
                         signal->group_stop_count = 0;
                         t = p;
                         do {
+                                task_clear_group_stop_pending(t);
                                 sigaddset(&t->pending.signal, SIGKILL);
                                 signal_wake_up(t, 1);
                         } while_each_thread(p, t);
@@ -909,14 +975,15 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
         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.  */
-
+        /*
+         * 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.
+         */
         if (sig < SIGRTMIN)
                 override_rlimit = (is_si_special(info) || info->si_code >= 0);
         else
@@ -1093,6 +1160,7 @@ int zap_other_threads(struct task_struct *p)
         p->signal->group_stop_count = 0;
 
         while_each_thread(p, t) {
+                task_clear_group_stop_pending(t);
                 count++;
 
                 /* Don't bother with already dead threads */
@@ -1105,22 +1173,30 @@ int zap_other_threads(struct task_struct *p)
         return count;
 }
 
-struct sighand_struct *lock_task_sighand(struct task_struct *tsk, unsigned long *flags)
+struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
+                                           unsigned long *flags)
 {
         struct sighand_struct *sighand;
 
-        rcu_read_lock();
         for (;;) {
+                local_irq_save(*flags);
+                rcu_read_lock();
                 sighand = rcu_dereference(tsk->sighand);
-                if (unlikely(sighand == NULL))
+                if (unlikely(sighand == NULL)) {
+                        rcu_read_unlock();
+                        local_irq_restore(*flags);
                         break;
+                }
 
-                spin_lock_irqsave(&sighand->siglock, *flags);
-                if (likely(sighand == tsk->sighand))
+                spin_lock(&sighand->siglock);
+                if (likely(sighand == tsk->sighand)) {
+                        rcu_read_unlock();
                         break;
-                spin_unlock_irqrestore(&sighand->siglock, *flags);
+                }
+                spin_unlock(&sighand->siglock);
+                rcu_read_unlock();
+                local_irq_restore(*flags);
         }
-        rcu_read_unlock();
 
         return sighand;
 }
@@ -1186,8 +1262,7 @@ retry:
         return error;
 }
 
-int
-kill_proc_info(int sig, struct siginfo *info, pid_t pid)
+int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
 {
         int error;
         rcu_read_lock();
@@ -1284,8 +1359,7 @@ static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
  * These are for backward compatibility with the rest of the kernel source.
  */
 
-int
-send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
+int send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
         /*
          * Make sure legacy kernel users don't send in bad values
@@ -1353,7 +1427,7 @@ EXPORT_SYMBOL(kill_pid);
  * 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
+ * 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.
@@ -1521,16 +1595,30 @@ int do_notify_parent(struct task_struct *tsk, int sig)
         return ret;
 }
 
-static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
+/**
+ * do_notify_parent_cldstop - notify parent of stopped/continued state change
+ * @tsk: task reporting the state change
+ * @for_ptracer: the notification is for ptracer
+ * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
+ *
+ * Notify @tsk's parent that the stopped/continued state has changed.  If
+ * @for_ptracer is %false, @tsk's group leader notifies to its real parent.
+ * If %true, @tsk reports to @tsk->parent which should be the ptracer.
+ *
+ * CONTEXT:
+ * Must be called with tasklist_lock at least read locked.
+ */
+static void do_notify_parent_cldstop(struct task_struct *tsk,
+                                     bool for_ptracer, int why)
 {
         struct siginfo info;
         unsigned long flags;
         struct task_struct *parent;
         struct sighand_struct *sighand;
 
-        if (task_ptrace(tsk))
+        if (for_ptracer) {
                 parent = tsk->parent;
-        else {
+        } else {
                 tsk = tsk->group_leader;
                 parent = tsk->real_parent;
         }
@@ -1538,7 +1626,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
         info.si_signo = SIGCHLD;
         info.si_errno = 0;
         /*
-         * see comment in do_notify_parent() abot the following 3 lines
+         * see comment in do_notify_parent() about the following 4 lines
          */
         rcu_read_lock();
         info.si_pid = task_pid_nr_ns(tsk, parent->nsproxy->pid_ns);
@@ -1596,7 +1684,7 @@ static inline int may_ptrace_stop(void)
 }
 
 /*
- * Return nonzero if there is a SIGKILL that should be waking us up.
+ * Return non-zero if there is a SIGKILL that should be waking us up.
  * Called with the siglock held.
  */
 static int sigkill_pending(struct task_struct *tsk)
@@ -1606,6 +1694,15 @@ static int sigkill_pending(struct task_struct *tsk)
 }
 
 /*
+ * Test whether the target task of the usual cldstop notification - the
+ * real_parent of @child - is in the same group as the ptracer.
+ */
+static bool real_parent_is_ptracer(struct task_struct *child)
+{
+        return same_thread_group(child->parent, child->real_parent);
+}
+
+/*
  * This must be called with current->sighand->siglock held.
  *
  * This should be the path for all ptrace stops.
@@ -1616,8 +1713,12 @@ static int sigkill_pending(struct task_struct *tsk)
  * 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)
+static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
+        __releases(&current->sighand->siglock)
+        __acquires(&current->sighand->siglock)
 {
+        bool gstop_done = false;
+
         if (arch_ptrace_stop_needed(exit_code, info)) {
                 /*
                  * The arch code has something special to do before a
@@ -1638,21 +1739,49 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
         }
 
         /*
-         * If there is a group stop in progress,
-         * we must participate in the bookkeeping.
+         * If @why is CLD_STOPPED, we're trapping to participate in a group
+         * stop.  Do the bookkeeping.  Note that if SIGCONT was delievered
+         * while siglock was released for the arch hook, PENDING could be
+         * clear now.  We act as if SIGCONT is received after TASK_TRACED
+         * is entered - ignore it.
          */
-        if (current->signal->group_stop_count > 0)
-                --current->signal->group_stop_count;
+        if (why == CLD_STOPPED && (current->group_stop & GROUP_STOP_PENDING))
+                gstop_done = task_participate_group_stop(current);
 
         current->last_siginfo = info;
         current->exit_code = exit_code;
 
-        /* Let the debugger run.  */
-        __set_current_state(TASK_TRACED);
+        /*
+         * TRACED should be visible before TRAPPING is cleared; otherwise,
+         * the tracer might fail do_wait().
+         */
+        set_current_state(TASK_TRACED);
+
+        /*
+         * We're committing to trapping.  Clearing GROUP_STOP_TRAPPING and
+         * transition to TASK_TRACED should be atomic with respect to
+         * siglock.  This hsould be done after the arch hook as siglock is
+         * released and regrabbed across it.
+         */
+        task_clear_group_stop_trapping(current);
+
         spin_unlock_irq(&current->sighand->siglock);
         read_lock(&tasklist_lock);
         if (may_ptrace_stop()) {
-                do_notify_parent_cldstop(current, CLD_TRAPPED);
+                /*
+                 * Notify parents of the stop.
+                 *
+                 * While ptraced, there are two parents - the ptracer and
+                 * the real_parent of the group_leader.  The ptracer should
+                 * know about every stop while the real parent is only
+                 * interested in the completion of group stop.  The states
+                 * for the two don't interact with each other.  Notify
+                 * separately unless they're gonna be duplicates.
+                 */
+                do_notify_parent_cldstop(current, true, why);
+                if (gstop_done && !real_parent_is_ptracer(current))
+                        do_notify_parent_cldstop(current, false, why);
+
                 /*
                  * Don't want to allow preemption here, because
                  * sys_ptrace() needs this task to be inactive.
@@ -1667,7 +1796,16 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
                 /*
                  * By the time we got the lock, our tracer went away.
                  * Don't drop the lock yet, another tracer may come.
+                 *
+                 * If @gstop_done, the ptracer went away between group stop
+                 * completion and here.  During detach, it would have set
+                 * GROUP_STOP_PENDING on us and we'll re-enter TASK_STOPPED
+                 * in do_signal_stop() on return, so notifying the real
+                 * parent of the group stop completion is enough.
                  */
+                if (gstop_done)
+                        do_notify_parent_cldstop(current, false, why);
+
                 __set_current_state(TASK_RUNNING);
                 if (clear_code)
                         current->exit_code = 0;
@@ -1711,79 +1849,128 @@ void ptrace_notify(int exit_code)
 
         /* Let the debugger run.  */
         spin_lock_irq(&current->sighand->siglock);
-        ptrace_stop(exit_code, 1, &info);
+        ptrace_stop(exit_code, CLD_TRAPPED, 1, &info);
         spin_unlock_irq(&current->sighand->siglock);
 }
 
 /*
  * 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 non-zero 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 notify;
 
-        if (!sig->group_stop_count) {
+        if (!(current->group_stop & GROUP_STOP_PENDING)) {
+                unsigned int gstop = GROUP_STOP_PENDING | GROUP_STOP_CONSUME;
                 struct task_struct *t;
 
-                if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
+                /* signr will be recorded in task->group_stop for retries */
+                WARN_ON_ONCE(signr & ~GROUP_STOP_SIGMASK);
+
+                if (!likely(current->group_stop & GROUP_STOP_DEQUEUED) ||
                     unlikely(signal_group_exit(sig)))
                         return 0;
                 /*
-                 * There is no group stop already in progress.
-                 * We must initiate one now.
+                 * There is no group stop already in progress.  We must
+                 * initiate one now.
+                 *
+                 * While ptraced, a task may be resumed while group stop is
+                 * still in effect and then receive a stop signal and
+                 * initiate another group stop.  This deviates from the
+                 * usual behavior as two consecutive stop signals can't
+                 * cause two group stops when !ptraced.  That is why we
+                 * also check !task_is_stopped(t) below.
+                 *
+                 * The condition can be distinguished by testing whether
+                 * SIGNAL_STOP_STOPPED is already set.  Don't generate
+                 * group_exit_code in such case.
+                 *
+                 * This is not necessary for SIGNAL_STOP_CONTINUED because
+                 * an intervening stop signal is required to cause two
+                 * continued events regardless of ptrace.
                  */
-                sig->group_exit_code = signr;
+                if (!(sig->flags & SIGNAL_STOP_STOPPED))
+                        sig->group_exit_code = signr;
+                else
+                        WARN_ON_ONCE(!task_ptrace(current));
 
+                current->group_stop &= ~GROUP_STOP_SIGMASK;
+                current->group_stop |= signr | gstop;
                 sig->group_stop_count = 1;
-                for (t = next_thread(current); t != current; t = next_thread(t))
+                for (t = next_thread(current); t != current;
+                     t = next_thread(t)) {
+                        t->group_stop &= ~GROUP_STOP_SIGMASK;
                         /*
                          * 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)) {
+                        if (!(t->flags & PF_EXITING) && !task_is_stopped(t)) {
+                                t->group_stop |= signr | gstop;
                                 sig->group_stop_count++;
                                 signal_wake_up(t, 0);
                         }
+                }
         }
-        /*
-         * 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.
-         */
-        notify = sig->group_stop_count == 1 ? CLD_STOPPED : 0;
-        notify = tracehook_notify_jctl(notify, CLD_STOPPED);
-        /*
-         * tracehook_notify_jctl() can drop and reacquire siglock, so
-         * we keep ->group_stop_count != 0 before the call. If SIGCONT
-         * or SIGKILL comes in between ->group_stop_count == 0.
-         */
-        if (sig->group_stop_count) {
-                if (!--sig->group_stop_count)
-                        sig->flags = SIGNAL_STOP_STOPPED;
-                current->exit_code = sig->group_exit_code;
+retry:
+        if (likely(!task_ptrace(current))) {
+                int notify = 0;
+
+                /*
+                 * 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.
+                 */
+                if (task_participate_group_stop(current))
+                        notify = CLD_STOPPED;
+
                 __set_current_state(TASK_STOPPED);
+                spin_unlock_irq(&current->sighand->siglock);
+
+                /*
+                 * Notify the parent of the group stop completion.  Because
+                 * we're not holding either the siglock or tasklist_lock
+                 * here, ptracer may attach inbetween; however, this is for
+                 * group stop and should always be delivered to the real
+                 * parent of the group leader.  The new ptracer will get
+                 * its notification when this task transitions into
+                 * TASK_TRACED.
+                 */
+                if (notify) {
+                        read_lock(&tasklist_lock);
+                        do_notify_parent_cldstop(current, false, notify);
+                        read_unlock(&tasklist_lock);
+                }
+
+                /* Now we don't run again until woken by SIGCONT or SIGKILL */
+                schedule();
+
+                spin_lock_irq(&current->sighand->siglock);
+        } else {
+                ptrace_stop(current->group_stop & GROUP_STOP_SIGMASK,
+                            CLD_STOPPED, 0, NULL);
+                current->exit_code = 0;
         }
-        spin_unlock_irq(&current->sighand->siglock);
 
-        if (notify) {
-                read_lock(&tasklist_lock);
-                do_notify_parent_cldstop(current, notify);
-                read_unlock(&tasklist_lock);
+        /*
+         * GROUP_STOP_PENDING could be set if another group stop has
+         * started since being woken up or ptrace wants us to transit
+         * between TASK_STOPPED and TRACED.  Retry group stop.
+         */
+        if (current->group_stop & GROUP_STOP_PENDING) {
+                WARN_ON_ONCE(!(current->group_stop & GROUP_STOP_SIGMASK));
+                goto retry;
         }
 
-        /* Now we don't run again until woken by SIGCONT or SIGKILL */
-        do {
-                schedule();
-        } while (try_to_freeze());
+        /* PTRACE_ATTACH might have raced with task killing, clear trapping */
+        task_clear_group_stop_trapping(current);
+
+        spin_unlock_irq(&current->sighand->siglock);
 
         tracehook_finish_jctl();
-        current->exit_code = 0;
 
         return 1;
 }
@@ -1797,7 +1984,7 @@ static int ptrace_signal(int signr, siginfo_t *info,
         ptrace_signal_deliver(regs, cookie);
 
         /* Let the debugger run.  */
-        ptrace_stop(signr, 0, info);
+        ptrace_stop(signr, CLD_TRAPPED, 0, info);
 
         /* We're back.  Did the debugger cancel the sig?  */
         signr = current->exit_code;
@@ -1806,10 +1993,12 @@ static int ptrace_signal(int signr, siginfo_t *info,
 
         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.  */
+        /*
+         * 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;
@@ -1850,25 +2039,43 @@ relock:
          * the CLD_ si_code into SIGNAL_CLD_MASK bits.
          */
         if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
-                int why = (signal->flags & SIGNAL_STOP_CONTINUED)
-                                ? CLD_CONTINUED : CLD_STOPPED;
+                struct task_struct *leader;
+                int why;
+
+                if (signal->flags & SIGNAL_CLD_CONTINUED)
+                        why = CLD_CONTINUED;
+                else
+                        why = CLD_STOPPED;
+
                 signal->flags &= ~SIGNAL_CLD_MASK;
 
-                why = tracehook_notify_jctl(why, CLD_CONTINUED);
                 spin_unlock_irq(&sighand->siglock);
 
-                if (why) {
-                        read_lock(&tasklist_lock);
-                        do_notify_parent_cldstop(current->group_leader, why);
-                        read_unlock(&tasklist_lock);
-                }
+                /*
+                 * Notify the parent that we're continuing.  This event is
+                 * always per-process and doesn't make whole lot of sense
+                 * for ptracers, who shouldn't consume the state via
+                 * wait(2) either, but, for backward compatibility, notify
+                 * the ptracer of the group leader too unless it's gonna be
+                 * a duplicate.
+                 */
+                read_lock(&tasklist_lock);
+
+                do_notify_parent_cldstop(current, false, why);
+
+                leader = current->group_leader;
+                if (task_ptrace(leader) && !real_parent_is_ptracer(leader))
+                        do_notify_parent_cldstop(leader, true, why);
+
+                read_unlock(&tasklist_lock);
+
                 goto relock;
         }
 
         for (;;) {
                 struct k_sigaction *ka;
                 /*
-                 * Tracing can induce an artifical signal and choose sigaction.
+                 * Tracing can induce an artificial signal and choose sigaction.
                  * The return value in @signr determines the default action,
                  * but @info->si_signo is the signal number we will report.
                  */
@@ -1878,8 +2085,8 @@ relock:
                 if (unlikely(signr != 0))
                         ka = return_ka;
                 else {
-                        if (unlikely(signal->group_stop_count > 0) &&
-                            do_signal_stop(0))
+                        if (unlikely(current->group_stop &
+                                     GROUP_STOP_PENDING) && do_signal_stop(0))
                                 goto relock;
 
                         signr = dequeue_signal(current, &current->blocked,
@@ -1998,10 +2205,42 @@ relock:
         return signr;
 }
 
+/*
+ * It could be that complete_signal() picked us to notify about the
+ * group-wide signal. Other threads should be notified now to take
+ * the shared signals in @which since we will not.
+ */
+static void retarget_shared_pending(struct task_struct *tsk, sigset_t *which)
+{
+        sigset_t retarget;
+        struct task_struct *t;
+
+        sigandsets(&retarget, &tsk->signal->shared_pending.signal, which);
+        if (sigisemptyset(&retarget))
+                return;
+
+        t = tsk;
+        while_each_thread(tsk, t) {
+                if (t->flags & PF_EXITING)
+                        continue;
+
+                if (!has_pending_signals(&retarget, &t->blocked))
+                        continue;
+                /* Remove the signals this thread can handle. */
+                sigandsets(&retarget, &retarget, &t->blocked);
+
+                if (!signal_pending(t))
+                        signal_wake_up(t, 0);
+
+                if (sigisemptyset(&retarget))
+                        break;
+        }
+}
+
 void exit_signals(struct task_struct *tsk)
 {
         int group_stop = 0;
-        struct task_struct *t;
+        sigset_t unblocked;
 
         if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
                 tsk->flags |= PF_EXITING;
@@ -2017,25 +2256,23 @@ void exit_signals(struct task_struct *tsk)
         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);
+        unblocked = tsk->blocked;
+        signotset(&unblocked);
+        retarget_shared_pending(tsk, &unblocked);
 
-        if (unlikely(tsk->signal->group_stop_count) &&
-                        !--tsk->signal->group_stop_count) {
-                tsk->signal->flags = SIGNAL_STOP_STOPPED;
-                group_stop = tracehook_notify_jctl(CLD_STOPPED, CLD_STOPPED);
-        }
+        if (unlikely(tsk->group_stop & GROUP_STOP_PENDING) &&
+            task_participate_group_stop(tsk))
+                group_stop = CLD_STOPPED;
 out:
         spin_unlock_irq(&tsk->sighand->siglock);
 
+        /*
+         * If group stop has completed, deliver the notification.  This
+         * should always go to the real parent of the group leader.
+         */
         if (unlikely(group_stop)) {
                 read_lock(&tasklist_lock);
-                do_notify_parent_cldstop(tsk, group_stop);
+                do_notify_parent_cldstop(tsk, false, group_stop);
                 read_unlock(&tasklist_lock);
         }
 }
@@ -2055,6 +2292,9 @@ EXPORT_SYMBOL(unblock_all_signals);
  * System call entry points.
  */
 
+/**
+ *  sys_restart_syscall - restart a system call
+ */
 SYSCALL_DEFINE0(restart_syscall)
 {
         struct restart_block *restart = &current_thread_info()->restart_block;
@@ -2066,11 +2306,33 @@ 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)
+static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
+{
+        if (signal_pending(tsk) && !thread_group_empty(tsk)) {
+                sigset_t newblocked;
+                /* A set of now blocked but previously unblocked signals. */
+                sigandnsets(&newblocked, newset, &current->blocked);
+                retarget_shared_pending(tsk, &newblocked);
+        }
+        tsk->blocked = *newset;
+        recalc_sigpending();
+}
+
+/**
+ * set_current_blocked - change current->blocked mask
+ * @newset: new mask
+ *
+ * It is wrong to change ->blocked directly, this helper should be used
+ * to ensure the process can't miss a shared signal we are going to block.
  */
+void set_current_blocked(const sigset_t *newset)
+{
+        struct task_struct *tsk = current;
+
+        spin_lock_irq(&tsk->sighand->siglock);
+        __set_task_blocked(tsk, newset);
+        spin_unlock_irq(&tsk->sighand->siglock);
+}
 
 /*
  * This is also useful for kernel threads that want to temporarily
@@ -2082,66 +2344,66 @@ long do_no_restart_syscall(struct restart_block *param)
  */
 int sigprocmask(int how, sigset_t *set, sigset_t *oldset)
 {
-        int error;
+        struct task_struct *tsk = current;
+        sigset_t newset;
 
-        spin_lock_irq(&current->sighand->siglock);
+        /* Lockless, only current can change ->blocked, never from irq */
         if (oldset)
-                *oldset = current->blocked;
+                *oldset = tsk->blocked;
 
-        error = 0;
         switch (how) {
         case SIG_BLOCK:
-                sigorsets(&current->blocked, &current->blocked, set);
+                sigorsets(&newset, &tsk->blocked, set);
                 break;
         case SIG_UNBLOCK:
-                signandsets(&current->blocked, &current->blocked, set);
+                sigandnsets(&newset, &tsk->blocked, set);
                 break;
         case SIG_SETMASK:
-                current->blocked = *set;
+                newset = *set;
                 break;
         default:
-                error = -EINVAL;
+                return -EINVAL;
         }
-        recalc_sigpending();
-        spin_unlock_irq(&current->sighand->siglock);
 
-        return error;
+        set_current_blocked(&newset);
+        return 0;
 }
 
-SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, set,
+/**
+ *  sys_rt_sigprocmask - change the list of currently blocked signals
+ *  @how: whether to add, remove, or set signals
+ *  @nset: stores pending signals
+ *  @oset: previous value of signal mask if non-null
+ *  @sigsetsize: size of sigset_t type
+ */
+SYSCALL_DEFINE4(rt_sigprocmask, int, how, sigset_t __user *, nset,
                 sigset_t __user *, oset, size_t, sigsetsize)
 {
-        int error = -EINVAL;
         sigset_t old_set, new_set;
+        int error;
 
         /* XXX: Don't preclude handling different sized sigset_t's.  */
         if (sigsetsize != sizeof(sigset_t))
-                goto out;
+                return -EINVAL;
 
-        if (set) {
-                error = -EFAULT;
-                if (copy_from_user(&new_set, set, sizeof(*set)))
-                        goto out;
+        old_set = current->blocked;
+
+        if (nset) {
+                if (copy_from_user(&new_set, nset, sizeof(sigset_t)))
+                        return -EFAULT;
                 sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
 
-                error = sigprocmask(how, &new_set, &old_set);
+                error = sigprocmask(how, &new_set, NULL);
                 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);
+                        return error;
+        }
 
-        set_old:
-                error = -EFAULT;
-                if (copy_to_user(oset, &old_set, sizeof(*oset)))
-                        goto out;
+        if (oset) {
+                if (copy_to_user(oset, &old_set, sizeof(sigset_t)))
+                        return -EFAULT;
         }
-        error = 0;
-out:
-        return error;
+
+        return 0;
 }
 
 long do_sigpending(void __user *set, unsigned long sigsetsize)
@@ -2166,8 +2428,14 @@ long do_sigpending(void __user *set, unsigned long sigsetsize)
 
 out:
         return error;
-}       
+}
 
+/**
+ *  sys_rt_sigpending - examine a pending signal that has been raised
+ *                      while blocked
+ *  @set: stores pending signals
+ *  @sigsetsize: size of sigset_t type or larger
+ */
 SYSCALL_DEFINE2(rt_sigpending, sigset_t __user *, set, size_t, sigsetsize)
 {
         return do_sigpending(set, sigsetsize);
@@ -2216,9 +2484,9 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
                 err |= __put_user(from->si_trapno, &to->si_trapno);
 #endif
 #ifdef BUS_MCEERR_AO
-                /* 
+                /*
                  * Other callers might not initialize the si_lsb field,
-                 * so check explicitely for the right codes here.
+                 * so check explicitly for the right codes here.
                  */
                 if (from->si_code == BUS_MCEERR_AR || from->si_code == BUS_MCEERR_AO)
                         err |= __put_user(from->si_addr_lsb, &to->si_addr_lsb);
@@ -2247,15 +2515,82 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from)
 
 #endif
 
+/**
+ *  do_sigtimedwait - wait for queued signals specified in @which
+ *  @which: queued signals to wait for
+ *  @info: if non-null, the signal's siginfo is returned here
+ *  @ts: upper bound on process time suspension
+ */
+int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
+                        const struct timespec *ts)
+{
+        struct task_struct *tsk = current;
+        long timeout = MAX_SCHEDULE_TIMEOUT;
+        sigset_t mask = *which;
+        int sig;
+
+        if (ts) {
+                if (!timespec_valid(ts))
+                        return -EINVAL;
+                timeout = timespec_to_jiffies(ts);
+                /*
+                 * We can be close to the next tick, add another one
+                 * to ensure we will wait at least the time asked for.
+                 */
+                if (ts->tv_sec || ts->tv_nsec)
+                        timeout++;
+        }
+
+        /*
+         * Invert the set of allowed signals to get those we want to block.
+         */
+        sigdelsetmask(&mask, sigmask(SIGKILL) | sigmask(SIGSTOP));
+        signotset(&mask);
+
+        spin_lock_irq(&tsk->sighand->siglock);
+        sig = dequeue_signal(tsk, &mask, info);
+        if (!sig && timeout) {
+                /*
+                 * None ready, temporarily unblock those we're interested
+                 * while we are sleeping in so that we'll be awakened when
+                 * they arrive. Unblocking is always fine, we can avoid
+                 * set_current_blocked().
+                 */
+                tsk->real_blocked = tsk->blocked;
+                sigandsets(&tsk->blocked, &tsk->blocked, &mask);
+                recalc_sigpending();
+                spin_unlock_irq(&tsk->sighand->siglock);
+
+                timeout = schedule_timeout_interruptible(timeout);
+
+                spin_lock_irq(&tsk->sighand->siglock);
+                __set_task_blocked(tsk, &tsk->real_blocked);
+                siginitset(&tsk->real_blocked, 0);
+                sig = dequeue_signal(tsk, &mask, info);
+        }
+        spin_unlock_irq(&tsk->sighand->siglock);
+
+        if (sig)
+                return sig;
+        return timeout ? -EINTR : -EAGAIN;
+}
+
+/**
+ *  sys_rt_sigtimedwait - synchronously wait for queued signals specified
+ *                      in @uthese
+ *  @uthese: queued signals to wait for
+ *  @uinfo: if non-null, the signal's siginfo is returned here
+ *  @uts: upper bound on process time suspension
+ *  @sigsetsize: size of sigset_t type
+ */
 SYSCALL_DEFINE4(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;
+        int ret;
 
         /* XXX: Don't preclude handling different sized sigset_t's.  */
         if (sigsetsize != sizeof(sigset_t))
@@ -2263,65 +2598,27 @@ SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
 
         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);
+        ret = do_sigtimedwait(&these, &info, uts ? &ts : NULL);
 
-        if (sig) {
-                ret = sig;
-                if (uinfo) {
-                        if (copy_siginfo_to_user(uinfo, &info))
-                                ret = -EFAULT;
-                }
-        } else {
-                ret = -EAGAIN;
-                if (timeout)
-                        ret = -EINTR;
+        if (ret > 0 && uinfo) {
+                if (copy_siginfo_to_user(uinfo, &info))
+                        ret = -EFAULT;
         }
 
         return ret;
 }
 
+/**
+ *  sys_kill - send a signal to a process
+ *  @pid: the PID of the process
+ *  @sig: signal to be sent
+ */
 SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
 {
         struct siginfo info;
@@ -2397,7 +2694,11 @@ SYSCALL_DEFINE3(tgkill, pid_t, tgid, pid_t, pid, int, sig)
         return do_tkill(tgid, pid, sig);
 }
 
-/*
+/**
+ *  sys_tkill - send signal to one specific task
+ *  @pid: the PID of the task
+ *  @sig: signal to be sent
+ *
  *  Send a signal to only one task, even if it's a CLONE_THREAD task.
  */
 SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
@@ -2409,6 +2710,12 @@ SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
         return do_tkill(0, pid, sig);
 }
 
+/**
+ *  sys_rt_sigqueueinfo - send signal information to a signal
+ *  @pid: the PID of the thread
+ *  @sig: signal to be sent
+ *  @uinfo: signal info to be sent
+ */
 SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
                 siginfo_t __user *, uinfo)
 {
@@ -2418,9 +2725,13 @@ SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
                 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)
+         * Nor can they impersonate a kill()/tgkill(), which adds source info.
+         */
+        if (info.si_code >= 0 || info.si_code == SI_TKILL) {
+                /* We used to allow any < 0 si_code */
+                WARN_ON_ONCE(info.si_code < 0);
                 return -EPERM;
+        }
         info.si_signo = sig;
 
         /* POSIX.1b doesn't mention process groups.  */
@@ -2434,9 +2745,13 @@ long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
                 return -EINVAL;
 
         /* 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)
+         * Nor can they impersonate a kill()/tgkill(), which adds source info.
+         */
+        if (info->si_code >= 0 || info->si_code == SI_TKILL) {
+                /* We used to allow any < 0 si_code */
+                WARN_ON_ONCE(info->si_code < 0);
                 return -EPERM;
+        }
         info->si_signo = sig;
 
         return do_send_specific(tgid, pid, sig, info);
@@ -2528,12 +2843,11 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s
 
                 error = -EINVAL;
                 /*
-                 *
-                 * Note - this code used to test ss_flags incorrectly
+                 * 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
+                 *        mechanism.
                  */
                 if (ss_flags != SS_DISABLE && ss_flags != SS_ONSTACK && ss_flags != 0)
                         goto out;
@@ -2567,6 +2881,10 @@ out:
 
 #ifdef __ARCH_WANT_SYS_SIGPENDING
 
+/**
+ *  sys_sigpending - examine pending signals
+ *  @set: where mask of pending signal is returned
+ */
 SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
 {
         return do_sigpending(set, sizeof(*set));
@@ -2575,60 +2893,65 @@ SYSCALL_DEFINE1(sigpending, old_sigset_t __user *, set)
 #endif
 
 #ifdef __ARCH_WANT_SYS_SIGPROCMASK
-/* Some platforms have their own version with special arguments others
-   support only sys_rt_sigprocmask.  */
+/**
+ *  sys_sigprocmask - examine and change blocked signals
+ *  @how: whether to add, remove, or set signals
+ *  @nset: signals to add or remove (if non-null)
+ *  @oset: previous value of signal mask if non-null
+ *
+ * Some platforms have their own version with special arguments;
+ * others support only sys_rt_sigprocmask.
+ */
 
-SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, set,
+SYSCALL_DEFINE3(sigprocmask, int, how, old_sigset_t __user *, nset,
                 old_sigset_t __user *, oset)
 {
-        int error;
         old_sigset_t old_set, new_set;
+        sigset_t new_blocked;
 
-        if (set) {
-                error = -EFAULT;
-                if (copy_from_user(&new_set, set, sizeof(*set)))
-                        goto out;
+        old_set = current->blocked.sig[0];
+
+        if (nset) {
+                if (copy_from_user(&new_set, nset, sizeof(*nset)))
+                        return -EFAULT;
                 new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP));
 
-                spin_lock_irq(&current->sighand->siglock);
-                old_set = current->blocked.sig[0];
+                new_blocked = current->blocked;
 
-                error = 0;
                 switch (how) {
-                default:
-                        error = -EINVAL;
-                        break;
                 case SIG_BLOCK:
-                        sigaddsetmask(&current->blocked, new_set);
+                        sigaddsetmask(&new_blocked, new_set);
                         break;
                 case SIG_UNBLOCK:
-                        sigdelsetmask(&current->blocked, new_set);
+                        sigdelsetmask(&new_blocked, new_set);
                         break;
                 case SIG_SETMASK:
-                        current->blocked.sig[0] = new_set;
+                        new_blocked.sig[0] = new_set;
                         break;
+                default:
+                        return -EINVAL;
                 }
 
-                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;
+                set_current_blocked(&new_blocked);
+        }
+
+        if (oset) {
                 if (copy_to_user(oset, &old_set, sizeof(*oset)))
-                        goto out;
+                        return -EFAULT;
         }
-        error = 0;
-out:
-        return error;
+
+        return 0;
 }
 #endif /* __ARCH_WANT_SYS_SIGPROCMASK */
 
 #ifdef __ARCH_WANT_SYS_RT_SIGACTION
+/**
+ *  sys_rt_sigaction - alter an action taken by a process
+ *  @sig: signal to be sent
+ *  @act: new sigaction
+ *  @oact: used to save the previous sigaction
+ *  @sigsetsize: size of sigset_t type
+ */
 SYSCALL_DEFINE4(rt_sigaction, int, sig,
                 const struct sigaction __user *, act,
                 struct sigaction __user *, oact,
@@ -2707,14 +3030,22 @@ SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
 
 SYSCALL_DEFINE0(pause)
 {
-        current->state = TASK_INTERRUPTIBLE;
-        schedule();
+        while (!signal_pending(current)) {
+                current->state = TASK_INTERRUPTIBLE;
+                schedule();
+        }
         return -ERESTARTNOHAND;
 }
 
 #endif
 
 #ifdef __ARCH_WANT_SYS_RT_SIGSUSPEND
+/**
+ *  sys_rt_sigsuspend - replace the signal mask for a value with the
+ *      @unewset value until a signal is received
+ *  @unewset: new signal mask value
+ *  @sigsetsize: size of sigset_t type
+ */
 SYSCALL_DEFINE2(rt_sigsuspend, sigset_t __user *, unewset, size_t, sigsetsize)
 {
         sigset_t newset;