Andrey Grodzovsky <Andrey.Grodzovsky at amd.com> writes: > On 04/25/2018 03:14 AM, Daniel Vetter wrote: >> On Tue, Apr 24, 2018 at 05:37:08PM -0400, Andrey Grodzovsky wrote: >>> >>> On 04/24/2018 05:21 PM, Eric W. Biederman wrote: >>>> Andrey Grodzovsky <Andrey.Grodzovsky at amd.com> writes: >>>> >>>>> 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, >>>> It doesn't mean that. Unless you are called by do_coredump (you >>>> aren't). >>> Looking in latest code here >>> https://elixir.bootlin.com/linux/v4.17-rc2/source/kernel/signal.c#L2449 >>> i see that current->flags |= PF_SIGNALED; is out side of >>> if (sig_kernel_coredump(signr)) {...} scope >> Ok I read some more about this, and I guess you go through process exit >> and then eventually close. But I'm not sure. >> >> The code in drm_sched_entity_fini also looks strange: You unpark the >> scheduler thread before you remove all the IBs. At least from the comment >> that doesn't sound like what you want to do. > > I think it should be safe for the dying scheduler entity since before that (in > drm_sched_entity_do_release) we set it's runqueue to NULL > so no new jobs will be dequeued form it by the scheduler thread. > >> >> But in general, PF_SIGNALED is really something deeply internal to the >> core (used for some book-keeping and accounting). The drm scheduler is the >> only thing looking at it, so smells like a layering violation. I suspect >> (but without knowing what you're actually trying to achive here can't be >> sure) you want to look at something else. >> >> E.g. PF_EXITING seems to be used in a lot more places to cancel stuff >> that's no longer relevant when a task exits, not PF_SIGNALED. There's the >> TIF_MEMDIE flag if you're hacking around issues with the oom-killer. >> >> This here on the other hand looks really fragile, and probably only does >> what you want to do by accident. >> -Daniel > > Yes , that what Eric also said and in the V2 patches i will try to change > PF_EXITING > > Another issue is changing wait_event_killable to wait_event_timeout where I need > to understand > what TO value is acceptable for all the drivers using the scheduler, or maybe it > should come as a property > of drm_sched_entity. It would not surprise me if you could pick a large value like 1 second and issue a warning if that time outever triggers. It sounds like the condition where we wait indefinitely today is because something went wrong in the driver. Eric
