On Tue, Apr 24, 2018 at 05:02:40PM -0400, Andrey Grodzovsky wrote: > > > On 04/24/2018 03:44 PM, Daniel Vetter wrote: > > On Tue, Apr 24, 2018 at 05:46:52PM +0200, Michel Dänzer wrote: > > > Adding the dri-devel list, since this is driver independent code. > > > > > > > > > On 2018-04-24 05:30 PM, Andrey Grodzovsky wrote: > > > > Avoid calling wait_event_killable when you are possibly being called > > > > from get_signal routine since in that case you end up in a deadlock > > > > where you are alreay blocked in singla processing any trying to wait > > > Multiple typos here, "[...] already blocked in signal processing and [...]"? > > > > > > > > > > on a new signal. > > > > > > > > Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com> > > > > --- > > > > drivers/gpu/drm/scheduler/gpu_scheduler.c | 5 +++-- > > > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c b/drivers/gpu/drm/scheduler/gpu_scheduler.c > > > > index 088ff2b..09fd258 100644 > > > > --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c > > > > +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c > > > > @@ -227,9 +227,10 @@ void drm_sched_entity_do_release(struct drm_gpu_scheduler *sched, > > > > return; > > > > /** > > > > * The client will not queue more IBs during this fini, consume existing > > > > - * queued IBs or discard them on SIGKILL > > > > + * queued IBs or discard them when in death signal state since > > > > + * wait_event_killable can't receive signals in that state. > > > > */ > > > > - if ((current->flags & PF_SIGNALED) && current->exit_code == SIGKILL) > > > > + if (current->flags & PF_SIGNALED) > > You want fatal_signal_pending() here, instead of inventing your own broken > > version. > > I rely on current->flags & PF_SIGNALED because this being set from within > get_signal, > meaning I am within signal processing in which case I want to avoid any > signal based wait for that task, > From what i see in the code, task_struct.pending.signal is being set for > other threads in same > group (zap_other_threads) or for other scenarios, those task are still able > to receive signals > so calling wait_event_killable there will not have problem. > > > > entity->fini_status = -ERESTARTSYS; > > > > else > > > > entity->fini_status = wait_event_killable(sched->job_scheduled, > > But really this smells like a bug in wait_event_killable, since > > wait_event_interruptible does not suffer from the same bug. It will return > > immediately when there's a signal pending. > > Even when wait_event_interruptible is called as following - > ...->do_signal->get_signal->....->wait_event_interruptible ? > I haven't tried it but wait_event_interruptible is very much alike to > wait_event_killable so I would assume it will also > not be interrupted if called like that. (Will give it a try just out of > curiosity anyway) wait_event_killabel doesn't check for fatal_signal_pending before calling schedule, so definitely has a nice race there. But if you're sure that you really need to check PF_SIGNALED, then I'm honestly not clear on what you're trying to pull off here. Your sparse explanation of what happens isn't enough, since I have no idea how you can get from get_signal() to the above wait_event_killable callsite. -Daniel > > Andrey > > > > > I think this should be fixed in core code, not papered over in some > > subsystem. > > -Daniel > > > > > > > > -- > > > Earthling Michel Dänzer | http://www.amd.com > > > Libre software enthusiast | Mesa and X developer > > > _______________________________________________ > > > dri-devel mailing list > > > dri-devel at lists.freedesktop.org > > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > _______________________________________________ > dri-devel mailing list > dri-devel at lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
