svn commit: r212841 - head/lib/libthr/thread

[David Xu]

Author: davidxu
Date: Sun Sep 19 09:03:11 2010
New Revision: 212841
URL: http://svn.freebsd.org/changeset/base/212841

Log:
  Because atfork lock is held while forking, a thread cancellation triggered
  by atfork handler is unsafe, use intenal flag no_cancel to disable it.

Modified:
  head/lib/libthr/thread/thr_exit.c
  head/lib/libthr/thread/thr_fork.c
  head/lib/libthr/thread/thr_private.h
  head/lib/libthr/thread/thr_sig.c

Modified: head/lib/libthr/thread/thr_exit.c
==============================================================================
--- head/lib/libthr/thread/thr_exit.c	Sun Sep 19 08:55:36 2010	(r212840)
+++ head/lib/libthr/thread/thr_exit.c	Sun Sep 19 09:03:11 2010	(r212841)
@@ -206,7 +206,7 @@ _pthread_exit_mask(void *status, sigset_
 
 	/* Flag this thread as exiting. */
 	curthread->cancelling = 1;
-	curthread->cancel_enable = 0;
+	curthread->no_cancel = 1;
 	curthread->cancel_async = 0;
 	curthread->cancel_point = 0;
 	if (mask != NULL)

Modified: head/lib/libthr/thread/thr_fork.c
==============================================================================
--- head/lib/libthr/thread/thr_fork.c	Sun Sep 19 08:55:36 2010	(r212840)
+++ head/lib/libthr/thread/thr_fork.c	Sun Sep 19 09:03:11 2010	(r212841)
@@ -137,7 +137,7 @@ _fork(void)
 	struct pthread *curthread;
 	struct pthread_atfork *af;
 	pid_t ret;
-	int errsave;
+	int errsave, cancelsave;
 	int was_threaded;
 	int rtld_locks[MAX_RTLD_LOCKS];
 
@@ -145,7 +145,8 @@ _fork(void)
 		return (__sys_fork());
 
 	curthread = _get_curthread();
-
+	cancelsave = curthread->no_cancel;
+	curthread->no_cancel = 1;
 	_thr_rwl_rdlock(&_thr_atfork_lock);
 
 	/* Run down atfork prepare handlers. */
@@ -223,6 +224,7 @@ _fork(void)
 				af->child();
 		}
 		_thr_rwlock_unlock(&_thr_atfork_lock);
+		curthread->no_cancel = cancelsave;
 	} else {
 		/* Parent process */
 		errsave = errno;
@@ -244,6 +246,9 @@ _fork(void)
 		}
 
 		_thr_rwlock_unlock(&_thr_atfork_lock);
+		curthread->no_cancel = cancelsave;
+		/* test async cancel */
+		_thr_testcancel(curthread);
 	}
 	errno = errsave;
 

Modified: head/lib/libthr/thread/thr_private.h
==============================================================================
--- head/lib/libthr/thread/thr_private.h	Sun Sep 19 08:55:36 2010	(r212840)
+++ head/lib/libthr/thread/thr_private.h	Sun Sep 19 09:03:11 2010	(r212841)
@@ -356,9 +356,9 @@ struct pthread {
 	struct pthread_attr	attr;
 
 #define	SHOULD_CANCEL(thr)					\
-	((thr)->cancel_pending &&				\
+	((thr)->cancel_pending && (thr)->cancel_enable &&	\
 	 ((thr)->cancel_point || (thr)->cancel_async) &&	\
-	 (thr)->cancel_enable && (thr)->cancelling == 0)
+	 (thr)->no_cancel == 0)
 
 	/* Cancellation is enabled */
 	int			cancel_enable;
@@ -369,8 +369,8 @@ struct pthread {
 	/* Thread is at cancellation point */
 	int			cancel_point;
 
-	/* Cancellation should be synchoronized */
-	int			cancel_defer;
+	/* Cancellation is temporarily disabled */
+	int			no_cancel;
 
 	/* Asynchronouse cancellation is enabled */
 	int			cancel_async;

Modified: head/lib/libthr/thread/thr_sig.c
==============================================================================
--- head/lib/libthr/thread/thr_sig.c	Sun Sep 19 08:55:36 2010	(r212840)
+++ head/lib/libthr/thread/thr_sig.c	Sun Sep 19 09:03:11 2010	(r212841)
@@ -187,7 +187,6 @@ handle_signal(struct sigaction *actp, in
 	struct pthread *curthread = _get_curthread();
 	ucontext_t uc2;
 	__siginfohandler_t *sigfunc;
-	int cancel_defer;
 	int cancel_point;
 	int cancel_async;
 	int cancel_enable;
@@ -213,12 +212,10 @@ handle_signal(struct sigaction *actp, in
 	 * cancellation is pending, to avoid this problem while thread is in
 	 * deferring mode, cancellation is temporarily disabled.
 	 */
-	cancel_defer = curthread->cancel_defer;
 	cancel_point = curthread->cancel_point;
 	cancel_async = curthread->cancel_async;
 	cancel_enable = curthread->cancel_enable;
 	curthread->cancel_point = 0;
-	curthread->cancel_defer = 0;
 	if (!cancel_async)
 		curthread->cancel_enable = 0;
 
@@ -245,7 +242,6 @@ handle_signal(struct sigaction *actp, in
 	err = errno;
 
 	curthread->in_sigsuspend = in_sigsuspend;
-	curthread->cancel_defer = cancel_defer;
 	curthread->cancel_point = cancel_point;
 	curthread->cancel_enable = cancel_enable;
 
@@ -275,7 +271,7 @@ check_cancel(struct pthread *curthread, 
 {
 
 	if (__predict_true(!curthread->cancel_pending || !curthread->cancel_enable ||
-	    curthread->cancelling))
+	    curthread->no_cancel))
 		return;
 
 	if (curthread->cancel_async) {