On 04/25, Daniel Vetter wrote: > > On Wed, Apr 25, 2018 at 3:22 PM, Oleg Nesterov <o...@redhat.com> wrote: > > On 04/24, Daniel Vetter wrote: > >> > >> wait_event_killabel doesn't check for fatal_signal_pending before calling > >> schedule, so definitely has a nice race there. > > > > This is fine. See the signal_pending_state() check in __schedule(). > > > > And this doesn't differ from wait_event_interruptible(), it too doesn't > > check signal_pending(), we rely on schedule() which must not block if the > > caller is signalled/killed. > > > > The problem is that it is not clear what should fatal_signal_pending() or > > even signal_pending() mean after exit_signals(). > > Uh, I was totally thrown off in all the wait_event* macros and somehow > landed in the _locked variants, which all need to recheck before they > drop the lock, for efficiency reasons. See do_wait_intr().
Just in case, note that do_wait_intr() has to check signal_pending() for completely differerent reason. We need to return non-zero code to stop the main loop in __wait_event_interruptible_locked(); unlike ___wait_event() it doesn't check signal_pending() itself. Oleg.
