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authorKirill Tkhai <ktkhai@parallels.com>2015-04-16 12:48:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-17 09:04:07 -0400
commitdfcce791fb0ad06f3f0b745a23160b9d8858fe39 (patch)
treea3c49070946f205a96642688af0daf5cd3c3c432 /fs/exec.c
parent6e399cd144d8500ffb5d40fa6848890e2580a80a (diff)
downloadop-kernel-dev-dfcce791fb0ad06f3f0b745a23160b9d8858fe39.zip
op-kernel-dev-dfcce791fb0ad06f3f0b745a23160b9d8858fe39.tar.gz
fs/exec.c:de_thread: move notify_count write under lock
We set sig->notify_count = -1 between RELEASE and ACQUIRE operations: spin_unlock_irq(lock); ... if (!thread_group_leader(tsk)) { ... for (;;) { sig->notify_count = -1; write_lock_irq(&tasklist_lock); There are no restriction on it so other processors may see this STORE mixed with other STOREs in both areas limited by the spinlocks. Probably, it may be reordered with the above sig->group_exit_task = tsk; sig->notify_count = zap_other_threads(tsk); in some way. Set it under tasklist_lock locked to be sure nothing will be reordered. Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/exec.c')
-rw-r--r--fs/exec.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/fs/exec.c b/fs/exec.c
index a5fef83..02bfd98 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -926,10 +926,14 @@ static int de_thread(struct task_struct *tsk)
if (!thread_group_leader(tsk)) {
struct task_struct *leader = tsk->group_leader;
- sig->notify_count = -1; /* for exit_notify() */
for (;;) {
threadgroup_change_begin(tsk);
write_lock_irq(&tasklist_lock);
+ /*
+ * Do this under tasklist_lock to ensure that
+ * exit_notify() can't miss ->group_exit_task
+ */
+ sig->notify_count = -1;
if (likely(leader->exit_state))
break;
__set_current_state(TASK_KILLABLE);
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