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@xxxxxxx> 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@xxxxxxx> > > > > > > --- > > > > > > 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. 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 > > Andrey > > > 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 > > > > > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
