lkml.org 
[lkml]   [2018]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/3] drm/scheduler: Don't call wait_event_killable for signaled process.
From
Date


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@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)

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@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel

\
 
 \ /
  Last update: 2018-04-24 23:03    [W:0.169 / U:2.592 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site