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[46.138.227.157]) by smtp.googlemail.com with ESMTPSA id t6sm1751911lfl.286.2022.01.18.09.30.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Jan 2022 09:30:54 -0800 (PST) Message-ID: <99353796-eea7-b765-f355-46e50f1b8773@gmail.com> Date: Tue, 18 Jan 2022 20:30:53 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH 1/8] signal: Make SIGKILL during coredumps an explicit special case Content-Language: en-US To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Linus Torvalds , Alexey Gladkov , Kyle Huey , Oleg Nesterov , Kees Cook , Al Viro References: <87a6ha4zsd.fsf@email.froward.int.ebiederm.org> <20211213225350.27481-1-ebiederm@xmission.com> <9363765f-9883-75ee-70f1-a1a8e9841812@gmail.com> <87pmp67y4r.fsf@email.froward.int.ebiederm.org> <5bbb54c4-7504-cd28-5dde-4e5965496625@gmail.com> <87bl0m14ew.fsf@email.froward.int.ebiederm.org> <6692758a-0af2-67e0-26fd-365625b3ad0c@gmail.com> <87iluqtcj3.fsf@email.froward.int.ebiederm.org> From: Dmitry Osipenko In-Reply-To: <87iluqtcj3.fsf@email.froward.int.ebiederm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 11.01.2022 20:20, Eric W. Biederman пишет: > Dmitry Osipenko writes: > >> 08.01.2022 21:13, Eric W. Biederman пишет: >>> Dmitry Osipenko writes: >>> >>>> 05.01.2022 22:58, Eric W. Biederman пишет: >>>>> >>>>> I have not yet been able to figure out how to run gst-pluggin-scanner in >>>>> a way that triggers this yet. In truth I can't figure out how to >>>>> run gst-pluggin-scanner in a useful way. >>>>> >>>>> I am going to set up some unit tests and see if I can reproduce your >>>>> hang another way, but if you could give me some more information on what >>>>> you are doing to trigger this I would appreciate it. >>>> >>>> Thanks, Eric. The distro is Arch Linux, but it's a development >>>> environment where I'm running latest GStreamer from git master. I'll try >>>> to figure out the reproduction steps and get back to you. >>> >>> Thank you. >>> >>> Until I can figure out why this is causing problems I have dropped the >>> following two patches from my queue: >>> signal: Make SIGKILL during coredumps an explicit special case >>> signal: Drop signals received after a fatal signal has been processed >>> >>> I have replaced them with the following two patches that just do what >>> is needed for the rest of the code in the series: >>> signal: Have prepare_signal detect coredumps using >>> signal: Make coredump handling explicit in complete_signal >>> >>> Perversely my failure to change the SIGKILL handling when coredumps are >>> happening proves to me that I need to change the SIGKILL handling when >>> coredumps are happening to make the code more maintainable. >> >> Eric, thank you again. I started to look at the reproduction steps and >> haven't completed it yet. Turned out the problem affects only older >> NVIDIA Tegra2 Cortex-A9 CPU that lacks support of ARM NEON instructions >> set, hence the problem isn't visible on x86 and other CPUs out of the >> box. I'll need to check whether the problem could be simulated on all >> arches or maybe it's specific to VFP exception handling of ARM32. > > It sounds like the gstreamer plugins only fail on certain hardware on > arm32, and things don't hang in coredumps unless the plugins fail. > That does make things tricky to minimize. > > I have just verified that the known problematic code is not > in linux-next for Jan 11 2022. > > If folks as they have time can double check linux-next and verify all is > well I would appreciate it. I don't expect that there are problems but > sometimes one problem hides another. Hello Eric, I reproduced the trouble on x86_64. Here are the reproduction steps, using ArchLinux and linux-next-20211224: ``` sudo pacman -S base-devel git mesa glu meson wget git clone https://github.com/grate-driver/gstreamer.git cd gstreamer git checkout sigill meson --prefix=/usr -Dgst-plugins-base:playback=enabled -Dgst-devtools:validate=disabled build cd build sudo ninja install wget https://www.peach.themazzone.com/big_buck_bunny_720p_h264.mov rm -r ~/.cache/gstreamer-1.0 gst-play-1.0 ./big_buck_bunny_720p_h264.mov ``` The SIGILL, thrown by [1], causes the hang. There is no hang using v5.16.1 kernel. [1] https://github.com/grate-driver/gstreamer/commit/006f9a2ee6dcf7b31c9b5413815d6054d82a3b2f