Import my recent 1:1 threading working. some features improved includes:

 1. fast simple type mutex.
 2. __thread tls works.
 3. asynchronous cancellation works ( using signal ).
 4. thread synchronization is fully based on umtx, mainly, condition
    variable and other synchronization objects were rewritten by using
    umtx directly. those objects can be shared between processes via
    shared memory, it has to change ABI which does not happen yet.
 5. default stack size is increased to 1M on 32 bits platform, 2M for
    64 bits platform.
As the result, some mysql super-smack benchmarks show performance is
improved massivly.

Okayed by: jeff, mtm, rwatson, scottl

1 files changed, 55 insertions, 10 deletions

diff --git a/lib/libthr/thread/thr_once.c b/lib/libthr/thread/thr_once.c
index cef478d..8716e75 100644
--- a/lib/libthr/thread/thr_once.c
+++ b/lib/libthr/thread/thr_once.c
@@ -31,23 +31,68 @@
  *
  * $FreeBSD$
  */
+
+#include "namespace.h"
 #include <pthread.h>
+#include "un-namespace.h"
+
 #include "thr_private.h"
 
 __weak_reference(_pthread_once, pthread_once);
 
+#define ONCE_NEVER_DONE		PTHREAD_NEEDS_INIT
+#define ONCE_DONE		PTHREAD_DONE_INIT
+#define	ONCE_IN_PROGRESS	0x02
+#define	ONCE_MASK		0x03
+
+static pthread_mutex_t		once_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t		once_cv = PTHREAD_COND_INITIALIZER;
+
+/*
+ * POSIX:
+ * The pthread_once() function is not a cancellation point. However,
+ * if init_routine is a cancellation point and is canceled, the effect
+ * on once_control shall be as if pthread_once() was never called.
+ */
+ 
+static void
+once_cancel_handler(void *arg)
+{
+	pthread_once_t *once_control = arg;
+
+	_pthread_mutex_lock(&once_lock);
+	once_control->state = ONCE_NEVER_DONE;
+	_pthread_mutex_unlock(&once_lock);
+	_pthread_cond_broadcast(&once_cv);
+}
+
 int
-_pthread_once(pthread_once_t * once_control, void (*init_routine) (void))
+_pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
 {
-	if (once_control->state == PTHREAD_NEEDS_INIT) {
-		if (_thread_initial == NULL)
-			_thread_init();
-		pthread_mutex_lock(&(once_control->mutex));
-		if (once_control->state == PTHREAD_NEEDS_INIT) {
-			init_routine();
-			once_control->state = PTHREAD_DONE_INIT;
-		}
-		pthread_mutex_unlock(&(once_control->mutex));
+	int wakeup = 0;
+
+	if (once_control->state == ONCE_DONE)
+		return (0);
+	_pthread_mutex_lock(&once_lock);
+	while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS)
+		_pthread_cond_wait(&once_cv, &once_lock);
+	/*
+	 * If previous thread was canceled, then the state still
+	 * could be ONCE_NEVER_DONE, we need to check it again.
+	 */
+	if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) {
+		once_control->state = ONCE_IN_PROGRESS;
+		_pthread_mutex_unlock(&once_lock);
+		_pthread_cleanup_push(once_cancel_handler, once_control);
+		init_routine();
+		_pthread_cleanup_pop(0);
+		_pthread_mutex_lock(&once_lock);
+		once_control->state = ONCE_DONE;
+		wakeup = 1;
 	}
+	_pthread_mutex_unlock(&once_lock);
+	if (wakeup)
+		_pthread_cond_broadcast(&once_cv);
 	return (0);
 }
+