From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751037AbeDXWNU convert rfc822-to-8bit (ORCPT ); Tue, 24 Apr 2018 18:13:20 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:52649 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750766AbeDXWNR (ORCPT ); Tue, 24 Apr 2018 18:13:17 -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> <87tvs05mik.fsf@xmission.com> <27d7d15b-f7c3-2a0a-af85-eb243526ac88@amd.com> Date: Tue, 24 Apr 2018 17:11:44 -0500 In-Reply-To: <27d7d15b-f7c3-2a0a-af85-eb243526ac88@amd.com> (Andrey Grodzovsky's message of "Tue, 24 Apr 2018 17:37:08 -0400") Message-ID: <87a7ts2r1b.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=1fB6BS-0000ri-6Z;;;mid=<87a7ts2r1b.fsf@xmission.com>;;;hst=in02.mta.xmission.com;;;ip=97.119.174.25;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX196qoI4w0h/NKmTC+qu2j4I/SDdWUWRqWo= 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: 0.4999] * -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 543 ms - load_scoreonly_sql: 0.03 (0.0%), signal_user_changed: 2.6 (0.5%), b_tie_ro: 1.74 (0.3%), parse: 1.01 (0.2%), extract_message_metadata: 15 (2.7%), get_uri_detail_list: 2.4 (0.4%), tests_pri_-1000: 7 (1.3%), tests_pri_-950: 1.24 (0.2%), tests_pri_-900: 1.04 (0.2%), tests_pri_-400: 28 (5.2%), check_bayes: 27 (5.0%), b_tokenize: 9 (1.7%), b_tok_get_all: 9 (1.6%), b_comp_prob: 2.9 (0.5%), b_tok_touch_all: 3.5 (0.6%), b_finish: 0.66 (0.1%), tests_pri_0: 230 (42.4%), check_dkim_signature: 0.54 (0.1%), check_dkim_adsp: 2.7 (0.5%), tests_pri_500: 254 (46.8%), poll_dns_idle: 247 (45.6%), 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 in02.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 05:21 PM, Eric W. Biederman wrote: >> 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). > > 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 In small words. You showed me the backtrace and I have read the code. PF_SIGNALED means you got killed by a signal. get_signal do_coredump do_group_exit do_exit exit_signals sets PF_EXITING exit_mm calls fput on mmaps calls sched_task_work exit_files calls fput on open files calls sched_task_work exit_task_work task_work_run /* you are here */ So strictly speaking you are inside of get_signal it is not meaningful to speak of yourself as within get_signal. I am a little surprised to see task_work_run called so early. I was mostly expecting it to happen when the dead task was scheduling away, like normally happens. Testing for PF_SIGNALED does not give you anything at all that testing for PF_EXITING (the flag that signal handling is shutdown) does not get you. There is no point in distinguishing PF_SIGNALED from any other path to do_exit. do_exit never returns. The task is dead. Blocking indefinitely while shutting down a task is a bad idea. Blocking indefinitely while closing a file descriptor is a bad idea. The task has been killed it can't get more dead. SIGKILL is meaningless at this point. So you need a timeout, or not to wait at all. Eric