Hi David, On Wed, Mar 25, 2015 at 08:31:49PM -0700, David Rientjes wrote: > On Wed, 25 Mar 2015, Johannes Weiner wrote: > > > exit_oom_victim() already knows that TIF_MEMDIE is set, and nobody > > else can clear it concurrently. Use clear_thread_flag() directly. > > > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > For the oom killer, that's true because of task_lock(): we always only set > TIF_MEMDIE when there is a valid p->mm and it's cleared in the exit path > after the unlock, acting as a barrier, when p->mm is set to NULL so it's > no longer a valid victim. So that part is fine. > > The problem is the android low memory killer that does > mark_tsk_oom_victim() without the protection of task_lock(), it's just rcu > protected so the reference to the task itself is guaranteed to still be > valid. But this is about *setting* it without a lock. My point was that once TIF_MEMDIE is actually set, the task owns it and nobody else can clear it for them, so it's safe to test and clear non-atomically from the task's own context. Am I missing something? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>