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Because atfork lock is held while forking, a thread cancellation triggered

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by atfork handler is unsafe, use intenal flag no_cancel to disable it.
This commit is contained in:
davidxu 2010-09-19 09:03:11 +00:00
parent 5418a23597
commit fe5567c8f1
4 changed files with 13 additions and 12 deletions
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2
lib/libthr/thread/thr_exit.c
View File

@ -206,7 +206,7 @@ _pthread_exit_mask(void *status, sigset_t *mask)
/* 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)

9
lib/libthr/thread/thr_fork.c
View File

@ -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;

8
lib/libthr/thread/thr_private.h
View File

@ -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;

6
lib/libthr/thread/thr_sig.c
View File

@ -187,7 +187,6 @@ handle_signal(struct sigaction *actp, int sig, siginfo_t *info, ucontext_t *ucp)
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, int sig, siginfo_t *info, ucontext_t *ucp)
* 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, int sig, siginfo_t *info, ucontext_t *ucp)
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, ucontext_t *ucp)
{
if (__predict_true(!curthread->cancel_pending || !curthread->cancel_enable ||
curthread->cancelling))
curthread->no_cancel))
return;
if (curthread->cancel_async) {