More signal handling fixups for the threaded signal fix upheavals.

This fixes the signal code to not wake up threads with blocked signals,
especially noticeable with kernel threads that may not be able to handle
signals at all.

We also don't unnecessarily wake processes in TASK_UNINTERRUPTIBLE.

kernel/signal.c

@@ -120,9 +120,6 @@ int max_queued_signals = 1024;
 #define SIG_KERNEL_STOP_MASK (\
 	M(SIGSTOP)   |  M(SIGTSTP)   |  M(SIGTTIN)   |  M(SIGTTOU)   )
 
-#define SIG_KERNEL_CONT_MASK (\
-	M(SIGCONT)   |  M(SIGKILL)   )
-
 #define SIG_KERNEL_COREDUMP_MASK (\
         M(SIGQUIT)   |  M(SIGILL)    |  M(SIGTRAP)   |  M(SIGABRT)   | \
         M(SIGFPE)    |  M(SIGSEGV)   |  M(SIGBUS)    |  M(SIGSYS)    | \
@@ -139,8 +136,6 @@ int max_queued_signals = 1024;
 		(((sig) < SIGRTMIN)  && T(sig, SIG_KERNEL_IGNORE_MASK))
 #define sig_kernel_stop(sig) \
 		(((sig) < SIGRTMIN)  && T(sig, SIG_KERNEL_STOP_MASK))
-#define sig_kernel_cont(sig) \
-		(((sig) < SIGRTMIN)  && T(sig, SIG_KERNEL_CONT_MASK))
 
 #define sig_user_defined(t, signr) \
 	(((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_DFL) &&	\
@@ -487,6 +482,8 @@ int dequeue_signal(sigset_t *mask, siginfo_t *info)
  */
 inline void signal_wake_up(struct task_struct *t, int resume)
 {
+	unsigned int mask;
+
 	set_tsk_thread_flag(t,TIF_SIGPENDING);
 
 	/*
@@ -508,8 +505,10 @@ inline void signal_wake_up(struct task_struct *t, int resume)
 	 * By calling wake_up_process any time resume is set, we ensure
 	 * the process will wake up and handle its stop or death signal.
 	 */
-	if ((t->state & TASK_INTERRUPTIBLE) ||
-	    (resume && t->state < TASK_ZOMBIE)) {
+	mask = TASK_INTERRUPTIBLE;
+	if (resume)
+		mask |= TASK_STOPPED;
+	if (t->state & mask) {
 		wake_up_process(t);
 		return;
 	}
@@ -591,8 +590,7 @@ static void handle_stop_signal(int sig, struct task_struct *p)
 			rm_from_queue(sigmask(SIGCONT), &t->pending);
 			t = next_thread(t);
 		} while (t != p);
-	}
-	else if (sig_kernel_cont(sig)) {
+	} else if (sig == SIGCONT) {
 		/*
 		 * Remove all stop signals from all queues,
 		 * and wake all threads.
@@ -637,17 +635,13 @@ static void handle_stop_signal(int sig, struct task_struct *p)
 			 * 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.  For SIGKILL, we likewise
-			 * don't want anybody doing anything but taking the
-			 * SIGKILL.  The only case in which a thread would
-			 * not already be in the signal dequeuing loop is
-			 * non-signal (e.g. syscall) ptrace tracing, so we
-			 * don't worry about an unnecessary trip through
-			 * the signal code and just keep this code path
-			 * simpler by unconditionally setting the flag.
+			 * the pending signal. 
 			 */
+			if (!(t->flags & PF_EXITING)) {
+				if (!sigismember(&t->blocked, SIGCONT))
 					set_tsk_thread_flag(t, TIF_SIGPENDING);
 				wake_up_process(t);
+			}
 			t = next_thread(t);
 		} while (t != p);
 	}
@@ -789,8 +783,9 @@ force_sig_specific(int sig, struct task_struct *t)
  * as soon as they're available, so putting the signal on the shared queue
  * will be equivalent to sending it to one such thread.
  */
-#define wants_signal(sig, p)	(!sigismember(&(p)->blocked, sig) \
-				 && (p)->state < TASK_STOPPED \
+#define wants_signal(sig, p, mask) 			\
+	(!sigismember(&(p)->blocked, sig)		\
+	 && !((p)->state & mask)			\
 	 && !((p)->flags & PF_EXITING)			\
 	 && (task_curr(p) || !signal_pending(p)))
 
@@ -798,6 +793,7 @@ static inline int
 __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 {
 	struct task_struct *t;
+	unsigned int mask;
 	int ret;
 
 #if CONFIG_SMP
@@ -814,6 +810,14 @@ __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 		/* This is a non-RT signal and we already have one queued.  */
 		return 0;
 
+	/*
+	 * Don't bother zombies and stopped tasks (but
+	 * SIGKILL will punch through stopped state)
+	 */
+	mask = TASK_DEAD | TASK_ZOMBIE;
+	if (sig != SIGKILL)
+		mask |= TASK_STOPPED;
+
 	/*
 	 * Put this signal on the shared-pending queue, or fail with EAGAIN.
 	 * We always use the shared queue for process-wide signals,
@@ -829,7 +833,7 @@ __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 	 * If the main thread wants the signal, it gets first crack.
 	 * Probably the least surprising to the average bear.
 	 */
-	if (wants_signal(sig, p))
+	if (wants_signal(sig, p, mask))
 		t = p;
 	else if (thread_group_empty(p))
 		/*
@@ -847,7 +851,7 @@ __group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
 			t = p->signal->curr_target = p;
 		BUG_ON(t->tgid != p->tgid);
 
-		while (!wants_signal(sig, t)) {
+		while (!wants_signal(sig, t, mask)) {
 			t = next_thread(t);
 			if (t == p->signal->curr_target)
 				/*