Messages in this thread | | | From | (Eric W. Biederman) | Date | Tue, 24 Apr 2018 11:23:18 -0500 | Subject | Re: [PATCH 2/3] drm/scheduler: Don't call wait_event_killable for signaled process. |
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Andrey Grodzovsky <andrey.grodzovsky@amd.com> writes:
> 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 > on a new signal.
I am curious what the call path that is problematic here.
In general waiting seems wrong when the process has already been fatally killed as indicated by PF_SIGNALED.
Returning -ERESTARTSYS seems wrong as nothing should make it back even to the edge of userspace here.
Given that this is the only use of PF_SIGNALED outside of bsd process accounting I find this code very suspicious.
It looks the code path that gets called during exit is buggy and needs to be sorted out.
Eric
> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@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) > entity->fini_status = -ERESTARTSYS; > else > entity->fini_status = wait_event_killable(sched->job_scheduled,
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