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). The closing of files does not happen in do_coredump. Which means you are being called from do_exit. In fact you are being called after exit_files which closes the files. The actual __fput processing happens in task_work_run. > 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. Excpet that you are geing called after from do_exit and after exit_files which is after exit_signal. Which means that PF_EXITING has been set. Which implies that the kernel signal handling machinery has already started being torn down. Not as much as I would like to happen at that point as we are still left with some old CLONE_PTHREAD messes in the code that need to be cleaned up. Still given the fact you are task_work_run it is quite possible even release_task has been run on that task before the f_op->release method is called. So you simply can not count on signals working. Which in practice leaves a timeout for ending your wait. That code can legitimately be in a context that is neither interruptible nor killable. >>>> 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) As PF_EXITING is set want_signal should fail and the signal state of the task should not be updatable by signals. Eric
