1 files changed, 17 insertions, 10 deletions

diff --git a/usr/src/lib/libc/port/threads/sigaction.c b/usr/src/lib/libc/port/threads/sigaction.c
index 529530f2af..3d8f747100 100644
--- a/usr/src/lib/libc/port/threads/sigaction.c
+++ b/usr/src/lib/libc/port/threads/sigaction.c
@@ -83,6 +83,9 @@ call_user_handler(int sig, siginfo_t *sip, ucontext_t *ucp)
 	 * while holding the sig's sig_lock for the least possible time.
 	 * We must acquire the sig's sig_lock because some thread running
 	 * in sigaction() might be establishing a new signal handler.
+	 * The code in sigaction() acquires the writer lock; here
+	 * we acquire the readers lock to ehance concurrency in the
+	 * face of heavy signal traffic, such as generated by java.
 	 *
 	 * Locking exceptions:
 	 * No locking for a child of vfork().
@@ -103,12 +106,12 @@ call_user_handler(int sig, siginfo_t *sip, ucontext_t *ucp)
 		/* we wish this assignment could be atomic */
 		(void) _private_memcpy(&uact, (void *)sap, sizeof (uact));
 	} else {
-		mutex_t *mp = &udp->siguaction[sig].sig_lock;
-		lmutex_lock(mp);
+		rwlock_t *rwlp = &udp->siguaction[sig].sig_lock;
+		lrw_rdlock(rwlp);
 		(void) _private_memcpy(&uact, (void *)sap, sizeof (uact));
 		if (sig == SIGCANCEL && (sap->sa_flags & SA_RESETHAND))
 			sap->sa_sigaction = SIG_DFL;
-		lmutex_unlock(mp);
+		lrw_unlock(rwlp);
 	}
 
 	/*
@@ -324,7 +327,7 @@ _libc_sigaction(int sig, const struct sigaction *nact, struct sigaction *oact)
 	}
 
 	if (!self->ul_vfork)
-		lmutex_lock(&udp->siguaction[sig].sig_lock);
+		lrw_wrlock(&udp->siguaction[sig].sig_lock);
 
 	oaction = udp->siguaction[sig].sig_uaction;
 
@@ -401,7 +404,7 @@ _libc_sigaction(int sig, const struct sigaction *nact, struct sigaction *oact)
 	}
 
 	if (!self->ul_vfork)
-		lmutex_unlock(&udp->siguaction[sig].sig_lock);
+		lrw_unlock(&udp->siguaction[sig].sig_lock);
 	return (rv);
 }
 
@@ -633,7 +636,7 @@ _sigprocmask(int how, const sigset_t *set, sigset_t *oset)
 
 /*
  * Called at library initialization to set up signal handling.
- * All we really do is initialize the sig_lock mutexes.
+ * All we really do is initialize the sig_lock rwlocks.
  * All signal handlers are either SIG_DFL or SIG_IGN on exec().
  * However, if any signal handlers were established on alternate
  * link maps before the primary link map has been initialized,
@@ -645,10 +648,14 @@ signal_init()
 	uberdata_t *udp = curthread->ul_uberdata;
 	struct sigaction *sap;
 	struct sigaction act;
+	rwlock_t *rwlp;
 	int sig;
 
 	for (sig = 0; sig < NSIG; sig++) {
-		udp->siguaction[sig].sig_lock.mutex_magic = MUTEX_MAGIC;
+		rwlp = &udp->siguaction[sig].sig_lock;
+		rwlp->rwlock_magic = RWL_MAGIC;
+		rwlp->mutex.mutex_flag = LOCK_INITED;
+		rwlp->mutex.mutex_magic = MUTEX_MAGIC;
 		sap = &udp->siguaction[sig].sig_uaction;
 		if (sap->sa_sigaction != SIG_DFL &&
 		    sap->sa_sigaction != SIG_IGN &&
@@ -694,13 +701,13 @@ void
 setup_cancelsig(int sig)
 {
 	uberdata_t *udp = curthread->ul_uberdata;
-	mutex_t *mp = &udp->siguaction[sig].sig_lock;
+	rwlock_t *rwlp = &udp->siguaction[sig].sig_lock;
 	struct sigaction act;
 
 	ASSERT(sig == SIGCANCEL || sig == SIGAIOCANCEL);
-	lmutex_lock(mp);
+	lrw_rdlock(rwlp);
 	act = udp->siguaction[sig].sig_uaction;
-	lmutex_unlock(mp);
+	lrw_unlock(rwlp);
 	if (act.sa_sigaction == SIG_DFL ||
 	    act.sa_sigaction == SIG_IGN)
 		act.sa_flags = SA_SIGINFO;