The patch titled
Subject: fs/exec.c:de_thread: move notify_count write under lock
has been added to the -mm tree. Its filename is
de_thread-move-notify_count-write-under-lock.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/de_thread-move-notify_count-write-under-lock.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/de_thread-move-notify_count-write-under-lock.patch
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------------------------------------------------------
From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxx>
Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/exec.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff -puN fs/exec.c~de_thread-move-notify_count-write-under-lock fs/exec.c
--- a/fs/exec.c~de_thread-move-notify_count-write-under-lock
+++ a/fs/exec.c
@@ -926,10 +926,14 @@ static int de_thread(struct task_struct
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);
_
Patches currently in -mm which might be from ktkhai@xxxxxxxxxxxxx are
de_thread-move-notify_count-write-under-lock.patch
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