From: Luis Chamberlain <mcgrof@kernel.org> To: rafael@kernel.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, jack@suse.cz, bvanassche@acm.org, jeyu@kernel.org, ebiederm@xmission.com Cc: mchehab@kernel.org, keescook@chromium.org, linux-fsdevel@vger.kernel.org, kernel@tuxforce.de, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Luis Chamberlain <mcgrof@kernel.org> Subject: [PATCH 0/2] fs: provide a stop gap fix for buggy resume firmware API calls Date: Fri, 16 Apr 2021 23:58:48 +0000 [thread overview] Message-ID: <20210416235850.23690-1-mcgrof@kernel.org> (raw) Lukas has reported an issue [0] with a media driver which causes stall on resume. At first his suspicion was that this issue was due to a bug in btrfs. I managed to build a custom driver to reproduce the issue and confirmed it was not a bug in btrfs. The issue is reproducible in XFS as well. This issue is a demonstration of how broken the filesystem suspend / resume cycle is and how easy it can be to trigger an issue. By only doing reads with the firmware API used incorrectly, a simple suspend / resume cycle can stall a system. The stall happens since the hardware never gets read request issued by the filesystem as it was already suspended. The fs waits forever. The stall also happens because resume calls are synchronous and if one does not complete we'll wait forever. My new unposted VFS series for the fs freezer / resume work fixes this, however this series will require a bit more discussion before this lands upstream. And so this series provides a test case for the issue and an intermediate stop-gap patch which resolves the issue for now. We can remove this once the VFS freeze work lands upstream. [0] https://lkml.kernel.org/r/c79e24a5-f808-d1f0-1f09-ee6f135d9679@tuxforce.de Luis Chamberlain (2): test_firmware: add suspend support to test buggy drivers fs/kernel_read_file: use usermodehelper_read_trylock() as a stop gap fs/kernel_read_file.c | 37 ++++- kernel/kexec_file.c | 9 +- kernel/module.c | 8 +- lib/test_firmware.c | 136 ++++++++++++++++-- tools/testing/selftests/firmware/fw_lib.sh | 8 +- .../selftests/firmware/fw_test_resume.sh | 80 +++++++++++ 6 files changed, 261 insertions(+), 17 deletions(-) create mode 100755 tools/testing/selftests/firmware/fw_test_resume.sh -- 2.29.2
WARNING: multiple messages have this Message-ID (diff)
From: Luis Chamberlain <mcgrof@kernel.org> To: rafael@kernel.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, jack@suse.cz, bvanassche@acm.org, jeyu@kernel.org, ebiederm@xmission.com Cc: mchehab@kernel.org, keescook@chromium.org, linux-fsdevel@vger.kernel.org, kernel@tuxforce.de, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Luis Chamberlain <mcgrof@kernel.org> Subject: [PATCH 0/2] fs: provide a stop gap fix for buggy resume firmware API calls Date: Fri, 16 Apr 2021 23:58:48 +0000 [thread overview] Message-ID: <20210416235850.23690-1-mcgrof@kernel.org> (raw) Lukas has reported an issue [0] with a media driver which causes stall on resume. At first his suspicion was that this issue was due to a bug in btrfs. I managed to build a custom driver to reproduce the issue and confirmed it was not a bug in btrfs. The issue is reproducible in XFS as well. This issue is a demonstration of how broken the filesystem suspend / resume cycle is and how easy it can be to trigger an issue. By only doing reads with the firmware API used incorrectly, a simple suspend / resume cycle can stall a system. The stall happens since the hardware never gets read request issued by the filesystem as it was already suspended. The fs waits forever. The stall also happens because resume calls are synchronous and if one does not complete we'll wait forever. My new unposted VFS series for the fs freezer / resume work fixes this, however this series will require a bit more discussion before this lands upstream. And so this series provides a test case for the issue and an intermediate stop-gap patch which resolves the issue for now. We can remove this once the VFS freeze work lands upstream. [0] https://lkml.kernel.org/r/c79e24a5-f808-d1f0-1f09-ee6f135d9679@tuxforce.de Luis Chamberlain (2): test_firmware: add suspend support to test buggy drivers fs/kernel_read_file: use usermodehelper_read_trylock() as a stop gap fs/kernel_read_file.c | 37 ++++- kernel/kexec_file.c | 9 +- kernel/module.c | 8 +- lib/test_firmware.c | 136 ++++++++++++++++-- tools/testing/selftests/firmware/fw_lib.sh | 8 +- .../selftests/firmware/fw_test_resume.sh | 80 +++++++++++ 6 files changed, 261 insertions(+), 17 deletions(-) create mode 100755 tools/testing/selftests/firmware/fw_test_resume.sh -- 2.29.2 _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
next reply other threads:[~2021-04-16 23:59 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-16 23:58 Luis Chamberlain [this message] 2021-04-16 23:58 ` [PATCH 0/2] fs: provide a stop gap fix for buggy resume firmware API calls Luis Chamberlain 2021-04-16 23:58 ` [PATCH 1/2] test_firmware: add suspend support to test buggy drivers Luis Chamberlain 2021-04-16 23:58 ` Luis Chamberlain 2021-04-21 22:23 ` Lukas Middendorf 2021-04-21 22:23 ` Lukas Middendorf 2021-04-16 23:58 ` [PATCH 2/2] fs/kernel_read_file: use usermodehelper_read_trylock() as a stop gap Luis Chamberlain 2021-04-16 23:58 ` Luis Chamberlain 2021-04-19 18:15 ` Luis Chamberlain 2021-04-19 18:15 ` Luis Chamberlain 2021-04-21 20:42 ` Lukas Middendorf 2021-04-21 20:42 ` Lukas Middendorf
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