Messages in this thread Patch in this message | | | Subject | [PATCH] de_thread: Move notify_count write under lock | From | Kirill Tkhai <> | Date | Thu, 5 Feb 2015 16:13:20 +0300 |
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The write operation may be reordered with the setting of group_exit_task. If so, this fires in exit_notify().
Looks like, it's not good to add smp barriers for this case, especially in exit_notify(), so let's put the notify_count write under write lock.
Signed-off-by: Kirill Tkhai <ktkhai@parallels.com> --- fs/exec.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/exec.c b/fs/exec.c index ad8798e..42782d5 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -920,10 +920,16 @@ 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); + /* + * We could set it once outside the for() cycle, but + * this requires to use SMP barriers there and in + * exit_notify(), because the write operation may + * be reordered with the setting of group_exit_task. + */ + sig->notify_count = -1; /* for exit_notify() */ if (likely(leader->exit_state)) break; __set_current_state(TASK_KILLABLE);
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