From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751150AbeDXVWg convert rfc822-to-8bit (ORCPT ); Tue, 24 Apr 2018 17:22:36 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:44298 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750735AbeDXVWf (ORCPT ); Tue, 24 Apr 2018 17:22:35 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Andrey Grodzovsky Cc: Michel =?utf-8?Q?D=C3=A4nzer?= , linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, David.Panariti@amd.com, oleg@redhat.com, Alexander.Deucher@amd.com, akpm@linux-foundation.org, Christian.Koenig@amd.com References: <1524583836-12130-1-git-send-email-andrey.grodzovsky@amd.com> <1524583836-12130-3-git-send-email-andrey.grodzovsky@amd.com> <7313704c-0693-0bb9-8818-99cd2b7c0ca0@daenzer.net> <20180424194418.GE25142@phenom.ffwll.local> Date: Tue, 24 Apr 2018 16:21:07 -0500 In-Reply-To: (Andrey Grodzovsky's message of "Tue, 24 Apr 2018 17:02:40 -0400") Message-ID: <87tvs05mik.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-XM-SPF: eid=1fB5OT-0004AP-3e;;;mid=<87tvs05mik.fsf@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=97.119.174.25;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/ArEztPnLNOmOoI1U6BgYLHs/Ovj5FFf0= X-SA-Exim-Connect-IP: 97.119.174.25 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.7 XMSubLong Long Subject * 1.5 XMNoVowels Alpha-numberic number with no vowels * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_02 5+ unique symbols in subject * 0.0 T_TooManySym_01 4+ unique symbols in subject * 0.1 XMSolicitRefs_0 Weightloss drug * 0.0 T_TooManySym_03 6+ unique symbols in subject X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **;Andrey Grodzovsky X-Spam-Relay-Country: X-Spam-Timing: total 539 ms - load_scoreonly_sql: 0.04 (0.0%), signal_user_changed: 2.4 (0.5%), b_tie_ro: 1.64 (0.3%), parse: 1.49 (0.3%), extract_message_metadata: 19 (3.6%), get_uri_detail_list: 4.2 (0.8%), tests_pri_-1000: 8 (1.5%), tests_pri_-950: 1.72 (0.3%), tests_pri_-900: 1.51 (0.3%), tests_pri_-400: 39 (7.3%), check_bayes: 38 (7.0%), b_tokenize: 17 (3.1%), b_tok_get_all: 10 (1.8%), b_comp_prob: 5.0 (0.9%), b_tok_touch_all: 3.3 (0.6%), b_finish: 0.68 (0.1%), tests_pri_0: 265 (49.2%), check_dkim_signature: 0.78 (0.1%), check_dkim_adsp: 2.8 (0.5%), tests_pri_500: 196 (36.4%), poll_dns_idle: 189 (35.0%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH 2/3] drm/scheduler: Don't call wait_event_killable for signaled process. X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrey Grodzovsky 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 >>>> --- >>>> 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