From: GNU Libc Maintainers <debian-glibc@lists.debian.org>
Date: Sat, 27 Aug 2022 11:38:11 +0000 (+0100)
Subject: git-cond-destroy
X-Git-Tag: archive/raspbian/2.34-7+rpi1~1^2~68
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=0742bcbe8cdbb2f3a32f8588a19af6b6e11fa894;p=glibc.git

git-cond-destroy

commit 4565083abc972bffe810e4151f8f3cb48531e526
Author: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date:   Mon Aug 22 22:27:24 2022 +0200

    htl: Make pthread*_cond_timedwait register wref before releasing mutex

    Otherwise another thread could be rightly trying to destroy the condition,
    see e.g. tst-cond20.


Gbp-Pq: Topic hurd-i386
Gbp-Pq: Name git-cond-destroy.diff
---

diff --git a/sysdeps/htl/pt-cond-timedwait.c b/sysdeps/htl/pt-cond-timedwait.c
index 0bc23099a..44d2cb774 100644
--- a/sysdeps/htl/pt-cond-timedwait.c
+++ b/sysdeps/htl/pt-cond-timedwait.c
@@ -142,13 +142,15 @@ __pthread_cond_timedwait_internal (pthread_cond_t *cond,
 
   __pthread_mutex_unlock (&self->cancel_lock);
 
-  /* Release MUTEX before blocking.  */
-  __pthread_mutex_unlock (mutex);
-
   /* Increase the waiter reference count.  Relaxed MO is sufficient because
-     we only need to synchronize when decrementing the reference count.  */
+     we only need to synchronize when decrementing the reference count.
+     We however need to have the mutex held to prevent concurrency with
+     a pthread_cond_destroy.  */
   atomic_fetch_add_relaxed (&cond->__wrefs, 2);
 
+  /* Release MUTEX before blocking.  */
+  __pthread_mutex_unlock (mutex);
+
   /* Block the thread.  */
   if (abstime != NULL)
     err = __pthread_timedblock (self, abstime, clock_id);
diff --git a/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c b/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c
index f24cc1de0..e5f6f55b2 100644
--- a/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c
+++ b/sysdeps/mach/hurd/htl/pt-hurd-cond-timedwait.c
@@ -99,6 +99,12 @@ __pthread_hurd_cond_timedwait_internal (pthread_cond_t *cond,
   __pthread_spin_unlock (&cond->__lock);
   __spin_unlock (&ss->lock);
 
+  /* Increase the waiter reference count.  Relaxed MO is sufficient because
+     we only need to synchronize when decrementing the reference count.
+     We however need to have the mutex held to prevent concurrency with
+     a pthread_cond_destroy.  */
+  atomic_fetch_add_relaxed (&cond->__wrefs, 2);
+
   if (cancel)
     {
       /* Cancelled on entry.  Just leave the mutex locked.  */
@@ -111,10 +117,6 @@ __pthread_hurd_cond_timedwait_internal (pthread_cond_t *cond,
       /* Release MUTEX before blocking.  */
       __pthread_mutex_unlock (mutex);
 
-  /* Increase the waiter reference count.  Relaxed MO is sufficient because
-     we only need to synchronize when decrementing the reference count.  */
-  atomic_fetch_add_relaxed (&cond->__wrefs, 2);
-
       /* Block the thread.  */
       if (abstime != NULL)
 	err = __pthread_timedblock (self, abstime, clock_id);