Change signal handling to conform to POSIX specified semantics.

Before this change, a signal was delivered to each thread that
didn't have the signal masked.  Signals also improperly woke up
threads waiting on I/O.  With this change, signals are now
handled in the following way:

  o If a thread is waiting in a sigwait for the signal,
    then the thread is woken up.

  o If no threads are sigwait'ing on the signal and a
    thread is in a sigsuspend waiting for the signal,
    then the thread is woken up.

  o In the case that no threads are waiting or suspended
    on the signal, then the signal is delivered to the
    first thread we find that has the signal unmasked.

  o If no threads are waiting or suspended on the signal,
    and no threads have the signal unmasked, then the signal
    is added to the process wide pending signal set.  The
    signal will be delivered to the first thread that unmasks
    the signal.

If there is an installed signal handler, it is only invoked
if the chosen thread was not in a sigwait.

In the case that multiple threads are waiting or suspended
on a signal, or multiple threads have the signal unmasked,
we wake up/deliver the signal to the first thread we find.
The above rules still apply.

Reported by:	Scott Hess <scott@avantgo.com>
Reviewed by:	jb, jasone

4 files changed, 79 insertions, 27 deletions

diff --git a/lib/libpthread/thread/thr_fork.c b/lib/libpthread/thread/thr_fork.c
index 155416e..b8d72dc 100644
--- a/lib/libpthread/thread/thr_fork.c
+++ b/lib/libpthread/thread/thr_fork.c
@@ -164,6 +164,9 @@ fork(void)
 				}
 			}
 
+			/* Treat the current thread as the initial thread: */
+			_thread_initial = _thread_run;
+
 			/* Re-init the dead thread list: */
 			TAILQ_INIT(&_dead_list);
 
diff --git a/lib/libpthread/thread/thr_private.h b/lib/libpthread/thread/thr_private.h
index 8bf8113..70c7487 100644
--- a/lib/libpthread/thread/thr_private.h
+++ b/lib/libpthread/thread/thr_private.h
@@ -858,7 +858,12 @@ SCLASS	pthread_cond_t  _gc_cond
 /*
  * Array of signal actions for this process.
  */
-struct  sigaction _thread_sigact[NSIG];
+SCLASS struct  sigaction _thread_sigact[NSIG];
+
+/*
+ * Pending signals for this process.
+ */
+SCLASS sigset_t	_process_sigpending;
 
 /*
  * Scheduling queues:
@@ -944,7 +949,6 @@ int     _thread_create(pthread_t *,const pthread_attr_t *,void *(*start_routine)
 int     _thread_fd_lock(int, int, struct timespec *);
 int     _thread_fd_lock_debug(int, int, struct timespec *,char *fname,int lineno);
 void    _dispatch_signals(void);
-void    _thread_signal(pthread_t, int);
 int	_mutex_cv_lock(pthread_mutex_t *);
 int	_mutex_cv_unlock(pthread_mutex_t *);
 void	_mutex_notify_priochange(pthread_t);
diff --git a/lib/libpthread/thread/thr_sig.c b/lib/libpthread/thread/thr_sig.c
index 3f31a34..3830a1d 100644
--- a/lib/libpthread/thread/thr_sig.c
+++ b/lib/libpthread/thread/thr_sig.c
@@ -42,6 +42,9 @@
 #include <pthread.h>
 #include "pthread_private.h"
 
+/* Prototypes: */
+static void	_thread_signal(pthread_t pthread, int sig);
+
 /* Static variables: */
 static spinlock_t	signal_lock = _SPINLOCK_INITIALIZER;
 unsigned int		pending_sigs[NSIG];
@@ -62,6 +65,9 @@ _thread_sig_init(void)
 
 	/* Clear the lock: */
 	signal_lock.access_lock = 0;
+
+	/* Clear the process pending signals: */
+	sigemptyset(&_process_sigpending);
 }
 
 void
@@ -155,6 +161,7 @@ _thread_sig_handle(int sig, ucontext_t * scp)
 {
 	int		i;
 	pthread_t	pthread, pthread_next;
+	pthread_t	suspended_thread, signaled_thread;
 
 	/* Check if the signal requires a dump of thread information: */
 	if (sig == SIGINFO)
@@ -203,12 +210,15 @@ _thread_sig_handle(int sig, ucontext_t * scp)
 		}
 
 		/*
-		 * Enter a loop to process each thread in the waiting
-		 * list that is sigwait-ing on a signal.  Since POSIX
-		 * doesn't specify which thread will get the signal
-		 * if there are multiple waiters, we'll give it to the
-		 * first one we find.
+		 * Enter a loop to look for threads that have the
+		 * signal unmasked.  POSIX specifies that a thread
+		 * in a sigwait will get the signal over any other
+		 * threads.  Second preference will be threads in
+		 * in a sigsuspend.  If none of the above, then the
+		 * signal is delivered to the first thread we find.
 		 */
+		suspended_thread = NULL;
+		signaled_thread = NULL;
 		for (pthread = TAILQ_FIRST(&_waitingq);
 		    pthread != NULL; pthread = pthread_next) {
 			/*
@@ -226,22 +236,46 @@ _thread_sig_handle(int sig, ucontext_t * scp)
 				pthread->signo = sig;
 
 				/*
+				 * POSIX doesn't doesn't specify which thread
+				 * will get the signal if there are multiple
+				 * waiters, so we give it to the first thread
+				 * we find.
+				 *
 				 * Do not attempt to deliver this signal
 				 * to other threads.
 				 */
 				return;
 			}
+			else if (!sigismember(&pthread->sigmask, sig)) {
+				if (pthread->state == PS_SIGSUSPEND) {
+					if (suspended_thread == NULL)
+						suspended_thread = pthread;
+				} else if (signaled_thread == NULL)
+					signaled_thread = pthread;
+			}
 		}
 
 		/* Check if the signal is not being ignored: */
-		if (_thread_sigact[sig - 1].sa_handler != SIG_IGN)
-			/*
-			 * Enter a loop to process each thread in the linked
-			 * list: 
-			 */
-			TAILQ_FOREACH(pthread, &_thread_list, tle) {
+		if (_thread_sigact[sig - 1].sa_handler != SIG_IGN) {
+			if (suspended_thread == NULL &&
+			    signaled_thread == NULL)
+				/*
+				 * Add it to the set of signals pending
+				 * on the process:
+				 */
+				sigaddset(&_process_sigpending, sig);
+			else {
 				pthread_t pthread_saved = _thread_run;
 
+				/*
+				 * We only deliver the signal to one thread;
+				 * give preference to the suspended thread:
+				 */
+				if (suspended_thread != NULL)
+					pthread = suspended_thread;
+				else
+					pthread = signaled_thread;
+
 				/* Current thread inside critical region? */
 				if (_thread_run->sig_defer_count > 0)
 					pthread->sig_defer_count++;
@@ -260,6 +294,8 @@ _thread_sig_handle(int sig, ucontext_t * scp)
 				if (_thread_run->sig_defer_count > 0)
 					pthread->sig_defer_count--;
 			}
+
+		}
 	}
 
 	/* Returns nothing. */
@@ -267,7 +303,7 @@ _thread_sig_handle(int sig, ucontext_t * scp)
 }
 
 /* Perform thread specific actions in response to a signal: */
-void
+static void
 _thread_signal(pthread_t pthread, int sig)
 {
 	/*
@@ -284,6 +320,7 @@ _thread_signal(pthread_t pthread, int sig)
 	 */
 	case PS_COND_WAIT:
 	case PS_DEAD:
+	case PS_DEADLOCK:
 	case PS_FDLR_WAIT:
 	case PS_FDLW_WAIT:
 	case PS_FILE_WAIT:
@@ -293,6 +330,7 @@ _thread_signal(pthread_t pthread, int sig)
 	case PS_STATE_MAX:
 	case PS_SIGTHREAD:
 	case PS_SIGWAIT:
+	case PS_SPINBLOCK:
 	case PS_SUSPENDED:
 		/* Nothing to do here. */
 		break;
@@ -326,8 +364,9 @@ _thread_signal(pthread_t pthread, int sig)
 	case PS_POLL_WAIT:
 	case PS_SLEEP_WAIT:
 	case PS_SELECT_WAIT:
-		if (sig != SIGCHLD ||
-		    _thread_sigact[sig - 1].sa_handler != SIG_DFL) {
+		if ((_thread_sigact[sig - 1].sa_flags & SA_RESTART) == 0 &&
+		    (sig != SIGCHLD ||
+		     _thread_sigact[sig - 1].sa_handler != SIG_DFL)) {
 			/* Flag the operation as interrupted: */
 			pthread->interrupted = 1;
 
@@ -344,11 +383,10 @@ _thread_signal(pthread_t pthread, int sig)
 
 	case PS_SIGSUSPEND:
 		/*
-		 * Only wake up the thread if the signal is unblocked
-		 * and there is a handler installed for the signal.
+		 * Only wake up the thread if there is a handler installed
+		 * for the signal.
 		 */
-		if (!sigismember(&pthread->sigmask, sig) &&
-		    _thread_sigact[sig - 1].sa_handler != SIG_DFL) {
+		if (_thread_sigact[sig - 1].sa_handler != SIG_DFL) {
 			/* Change the state of the thread to run: */
 			PTHREAD_NEW_STATE(pthread,PS_RUNNING);
 
@@ -368,9 +406,10 @@ _dispatch_signals()
 
 	/*
 	 * Check if there are pending signals for the running
-	 * thread that aren't blocked:
+	 * thread or process that aren't blocked:
 	 */
 	sigset = _thread_run->sigpend;
+	SIGSETOR(sigset, _process_sigpending);
 	SIGSETNAND(sigset, _thread_run->sigmask);
 	if (SIGNOTEMPTY(sigset))
 		/* Look for all possible pending signals: */
@@ -381,10 +420,13 @@ _dispatch_signals()
 			 */
 			if (_thread_sigact[i - 1].sa_handler != SIG_DFL &&
 			    _thread_sigact[i - 1].sa_handler != SIG_IGN &&
-			    sigismember(&_thread_run->sigpend,i) &&
-			    !sigismember(&_thread_run->sigmask,i)) {
-				/* Clear the pending signal: */
-				sigdelset(&_thread_run->sigpend,i);
+			    sigismember(&sigset, i)) {
+				if (sigismember(&_thread_run->sigpend,i))
+					/* Clear the thread pending signal: */
+					sigdelset(&_thread_run->sigpend,i);
+				else
+					/* Clear the process pending signal: */
+					sigdelset(&_process_sigpending,i);
 
 				/*
 				 * Dispatch the signal via the custom signal
diff --git a/lib/libpthread/thread/thr_sigwait.c b/lib/libpthread/thread/thr_sigwait.c
index a67a57f..faa227e 100644
--- a/lib/libpthread/thread/thr_sigwait.c
+++ b/lib/libpthread/thread/thr_sigwait.c
@@ -72,6 +72,7 @@ sigwait(const sigset_t * set, int *sig)
 
 	/* Check to see if a pending signal is in the wait mask. */
 	tempset = _thread_run->sigpend;
+	SIGSETOR(tempset, _process_sigpending);
 	SIGSETAND(tempset, waitset);
 	if (SIGNOTEMPTY(tempset)) {
 		/* Enter a loop to find a pending signal: */
@@ -81,7 +82,10 @@ sigwait(const sigset_t * set, int *sig)
 		}
 
 		/* Clear the pending signal: */
-		sigdelset(&_thread_run->sigpend,i);
+		if (sigismember(&_thread_run->sigpend,i))
+			sigdelset(&_thread_run->sigpend,i);
+		else
+			sigdelset(&_process_sigpending,i);
 
 		/* Return the signal number to the caller: */
 		*sig = i;
@@ -108,7 +112,6 @@ sigwait(const sigset_t * set, int *sig)
 		}
 	}
 	if (ret == 0) {
-
 		/*
 		 * Save the wait signal mask.  The wait signal
 		 * mask is independent of the threads signal mask