Change atfork lock from mutex to rwlock, also make mutexes used by malloc()

module private type, when private type mutex is locked/unlocked, thread
critical region is entered or leaved. These changes makes fork()
async-signal safe which required by POSIX. Note that user's atfork handler
still needs to be async-signal safe, but it is not problem of libthr, it
is user's responsiblity.

1 files changed, 22 insertions, 19 deletions

diff --git a/lib/libthr/thread/thr_fork.c b/lib/libthr/thread/thr_fork.c
index 8e1ea6a..1ce7c6e 100644
--- a/lib/libthr/thread/thr_fork.c
+++ b/lib/libthr/thread/thr_fork.c
@@ -89,9 +89,9 @@ _pthread_atfork(void (*prepare)(void), void (*parent)(void),
 	af->prepare = prepare;
 	af->parent = parent;
 	af->child = child;
-	THR_UMUTEX_LOCK(curthread, &_thr_atfork_lock);
+	_thr_rwl_rdlock(&_thr_atfork_lock);
 	TAILQ_INSERT_TAIL(&_thr_atfork_list, af, qe);
-	THR_UMUTEX_UNLOCK(curthread, &_thr_atfork_lock);
+	_thr_rwl_unlock(&_thr_atfork_lock);
 	return (0);
 }
 
@@ -104,7 +104,7 @@ __pthread_cxa_finalize(struct dl_phdr_info *phdr_info)
 	_thr_check_init();
 
 	curthread = _get_curthread();
-	THR_UMUTEX_LOCK(curthread, &_thr_atfork_lock);
+	_thr_rwl_wrlock(&_thr_atfork_lock);
 	TAILQ_FOREACH_SAFE(af, &_thr_atfork_list, qe, af1) {
 		if (__elf_phdr_match_addr(phdr_info, af->prepare) ||
 		    __elf_phdr_match_addr(phdr_info, af->parent) ||
@@ -113,7 +113,7 @@ __pthread_cxa_finalize(struct dl_phdr_info *phdr_info)
 			free(af);
 		}
 	}
-	THR_UMUTEX_UNLOCK(curthread, &_thr_atfork_lock);
+	_thr_rwl_unlock(&_thr_atfork_lock);
 	_thr_tsd_unload(phdr_info);
 	_thr_sigact_unload(phdr_info);
 }
@@ -137,7 +137,7 @@ _fork(void)
 
 	curthread = _get_curthread();
 
-	THR_UMUTEX_LOCK(curthread, &_thr_atfork_lock);
+	_thr_rwl_rdlock(&_thr_atfork_lock);
 
 	/* Run down atfork prepare handlers. */
 	TAILQ_FOREACH_REVERSE(af, &_thr_atfork_list, atfork_head, qe) {
@@ -146,6 +146,12 @@ _fork(void)
 	}
 
 	/*
+	 * Block all signals until we reach a safe point.
+	 */
+	_thr_signal_block(curthread);
+	_thr_signal_prefork();
+
+	/*
 	 * All bets are off as to what should happen soon if the parent
 	 * process was not so kindly as to set up pthread fork hooks to
 	 * relinquish all running threads.
@@ -158,12 +164,6 @@ _fork(void)
 		was_threaded = 0;
 	}
 
-	/*
-	 * Block all signals until we reach a safe point.
-	 */
-	_thr_signal_block(curthread);
-	_thr_signal_prefork();
-
 	/* Fork a new process: */
 	if ((ret = __sys_fork()) == 0) {
 		/* Child process */
@@ -182,7 +182,7 @@ _fork(void)
 
 		/* clear other threads locked us. */
 		_thr_umutex_init(&curthread->lock);
-		_thr_umutex_init(&_thr_atfork_lock);
+		_mutex_fork(curthread);
 
 		_thr_signal_postfork_child();
 
@@ -192,13 +192,12 @@ _fork(void)
 
 		/* reinitialize libc spinlocks. */
 		_thr_spinlock_init();
-		_mutex_fork(curthread);
 
 		/* reinitalize library. */
 		_libpthread_init(curthread);
 
-		/* Ready to continue, unblock signals. */ 
-		_thr_signal_unblock(curthread);
+		/* atfork is reinitializeded by _libpthread_init()! */
+		_thr_rwl_rdlock(&_thr_atfork_lock);
 
 		if (was_threaded) {
 			__isthreaded = 1;
@@ -206,32 +205,36 @@ _fork(void)
 			__isthreaded = 0;
 		}
 
+		/* Ready to continue, unblock signals. */ 
+		_thr_signal_unblock(curthread);
+
 		/* Run down atfork child handlers. */
 		TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
 			if (af->child != NULL)
 				af->child();
 		}
+		_thr_rwlock_unlock(&_thr_atfork_lock);
 	} else {
 		/* Parent process */
 		errsave = errno;
 
 		_thr_signal_postfork();
 
-		/* Ready to continue, unblock signals. */ 
-		_thr_signal_unblock(curthread);
-
 		if (was_threaded) {
 			_rtld_atfork_post(rtld_locks);
 			_malloc_postfork();
 		}
 
+		/* Ready to continue, unblock signals. */ 
+		_thr_signal_unblock(curthread);
+
 		/* Run down atfork parent handlers. */
 		TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
 			if (af->parent != NULL)
 				af->parent();
 		}
 
-		THR_UMUTEX_UNLOCK(curthread, &_thr_atfork_lock);
+		_thr_rwlock_unlock(&_thr_atfork_lock);
 	}
 	errno = errsave;