Date: Thu, 3 Mar 2005 14:56:21 +0530 From: "Andriy Tkachuk" <andrit@ukr.net> To: "David Xu" <davidxu@freebsd.org> Cc: threads@freebsd.org Subject: Re: patch for threads/76690 - critical - fork hang in child for-lc_r Message-ID: <012901c51fd3$131e23b0$090210ac@BORJA>
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[-- Attachment #1 --]
> > > Hmm, libc_r and libpthread handle spinlock differently which malloc
> > > uses to protect itself, some real world benchmarks are better than
> this.
yes , you right, David. one have to check __isthreaded before
firing _SPINLOCK. there will be nothing wrong, because
static spinlock_t thread_lock = _SPINLOCK_INITIALIZER;
initialyzed regardless __isthreaded in malloc.c but
for optimization probably it is worth to add this check.
Take a look on updated patch.
btw: i don't see the unlock in child in libpthread. there must be two
unlocks
- in child & in parent, doesn't it? :
# grep __malloc_lock -r libpthread
libpthread/thread/thr_fork.c: _spinlock(__malloc_lock);
libpthread/thread/thr_fork.c: if ((_kse_isthreaded() != 0) &&
(__malloc_lock != NULL)) {
libpthread/thread/thr_fork.c: _spinunlock(__malloc_lock);
#
[-- Attachment #2 --]
diff -r -u lib/libc_r/uthread/uthread_fork.c lib.patched/libc_r/uthread/uthread_fork.c
--- lib/libc_r/uthread/uthread_fork.c Fri Dec 10 09:06:45 2004
+++ lib.patched/libc_r/uthread/uthread_fork.c Thu Mar 3 14:50:06 2005
@@ -68,8 +68,15 @@
af->prepare();
}
+ extern spinlock_t *__malloc_lock;
+ if (__isthreaded && __malloc_lock != NULL)
+ _SPINLOCK(__malloc_lock);
+
/* Fork a new process: */
if ((ret = __sys_fork()) != 0) {
+ if (__isthreaded && __malloc_lock != NULL)
+ _SPINUNLOCK(__malloc_lock);
+
/* Run down atfork parent handlers. */
TAILQ_FOREACH(af, &_atfork_list, qe) {
if (af->parent != NULL)
@@ -78,6 +85,9 @@
_pthread_mutex_unlock(&_atfork_mutex);
} else {
+ if (__isthreaded && __malloc_lock != NULL)
+ _SPINUNLOCK(__malloc_lock);
+
/* Close the pthread kernel pipe: */
__sys_close(_thread_kern_pipe[0]);
__sys_close(_thread_kern_pipe[1]);
help
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