Dmitry Osipenko <digetx@xxxxxxxxx> writes: > 11.01.2022 20:20, Eric W. Biederman пишет: >> Dmitry Osipenko <digetx@xxxxxxxxx> writes: >> >>> 08.01.2022 21:13, Eric W. Biederman пишет: >>>> Dmitry Osipenko <digetx@xxxxxxxxx> 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 Thank you. I will verify this works before I add my updated version to my signal-for-v5.18 branch. Have you by any chance tried a newer version of linux-next without commit fbc11520b58a ("signal: Make SIGKILL during coredumps an explicit special case") in it? If not I will double check that my pulling the commit out does not break in the case you have documented. Eric
