Kernel Oops #2684
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There's a good chance this is related to #2523. |
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Thanks. I've installed your commit 59e9418 , so I'll run with that in place for now and watch it. |
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I was hit by the same bug while taking a snapshot |
behlendorf
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Dec 19, 2014
It is known that mutexes in Linux are not safe when using them to synchronize the freeing of object in which the mutex is embedded: http://lwn.net/Articles/575477/ The known places in ZFS which are suspected to suffer from the race condition are zio->io_lock and dbuf->db_mtx. * zio uses zio->io_lock and zio->io_cv to synchronize freeing between zio_wait() and zio_done(). * dbuf uses dbuf->db_mtx to protect reference counting. This patch fixes this kind of race by forcing serialization on mutex_exit() with a spin lock, making the mutex safe by sacrificing a bit of performance and memory overhead. This issue most commonly manifests itself as a deadlock in the zio pipeline caused by a process spinning on the damaged mutex. Similar deadlocks have been reported for the dbuf->db_mtx mutex. And it can also cause a NULL dereference or bad paging request under the right circumstances. This issue any many like it are linked off the openzfs/zfs#2523 issue. Specifically this fix resolves at least the following outstanding issues: openzfs/zfs#401 openzfs/zfs#2523 openzfs/zfs#2679 openzfs/zfs#2684 openzfs/zfs#2704 openzfs/zfs#2708 openzfs/zfs#2517 openzfs/zfs#2827 openzfs/zfs#2850 openzfs/zfs#2891 openzfs/zfs#2897 openzfs/zfs#2247 openzfs/zfs#2939 Signed-off-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Yao <ryao@gentoo.org> Closes #421
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This issue which is a duplicate of #2523 was resolved by the following commit. Full details can be found in the commit message and related lwn article. openzfs/spl@a3c1eb7 mutex: force serialization on mutex_exit() to fix races |
dajhorn
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Dec 20, 2014
Commit: openzfs/zfs@a3c1eb7 From: Chunwei Chen <tuxoko@gmail.com> Date: Fri, 19 Dec 2014 11:31:59 +0800 Subject: mutex: force serialization on mutex_exit() to fix races It is known that mutexes in Linux are not safe when using them to synchronize the freeing of object in which the mutex is embedded: http://lwn.net/Articles/575477/ The known places in ZFS which are suspected to suffer from the race condition are zio->io_lock and dbuf->db_mtx. * zio uses zio->io_lock and zio->io_cv to synchronize freeing between zio_wait() and zio_done(). * dbuf uses dbuf->db_mtx to protect reference counting. This patch fixes this kind of race by forcing serialization on mutex_exit() with a spin lock, making the mutex safe by sacrificing a bit of performance and memory overhead. This issue most commonly manifests itself as a deadlock in the zio pipeline caused by a process spinning on the damaged mutex. Similar deadlocks have been reported for the dbuf->db_mtx mutex. And it can also cause a NULL dereference or bad paging request under the right circumstances. This issue any many like it are linked off the openzfs/zfs#2523 issue. Specifically this fix resolves at least the following outstanding issues: openzfs/zfs#401 openzfs/zfs#2523 openzfs/zfs#2679 openzfs/zfs#2684 openzfs/zfs#2704 openzfs/zfs#2708 openzfs/zfs#2517 openzfs/zfs#2827 openzfs/zfs#2850 openzfs/zfs#2891 openzfs/zfs#2897 openzfs/zfs#2247 openzfs/zfs#2939 Signed-off-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Yao <ryao@gentoo.org> Backported-by: Darik Horn <dajhorn@vanadac.com> Closes #421 Conflicts: include/sys/mutex.h
behlendorf
pushed a commit
to openzfs/spl
that referenced
this issue
Dec 23, 2014
It is known that mutexes in Linux are not safe when using them to synchronize the freeing of object in which the mutex is embedded: http://lwn.net/Articles/575477/ The known places in ZFS which are suspected to suffer from the race condition are zio->io_lock and dbuf->db_mtx. * zio uses zio->io_lock and zio->io_cv to synchronize freeing between zio_wait() and zio_done(). * dbuf uses dbuf->db_mtx to protect reference counting. This patch fixes this kind of race by forcing serialization on mutex_exit() with a spin lock, making the mutex safe by sacrificing a bit of performance and memory overhead. This issue most commonly manifests itself as a deadlock in the zio pipeline caused by a process spinning on the damaged mutex. Similar deadlocks have been reported for the dbuf->db_mtx mutex. And it can also cause a NULL dereference or bad paging request under the right circumstances. This issue any many like it are linked off the openzfs/zfs#2523 issue. Specifically this fix resolves at least the following outstanding issues: openzfs/zfs#401 openzfs/zfs#2523 openzfs/zfs#2679 openzfs/zfs#2684 openzfs/zfs#2704 openzfs/zfs#2708 openzfs/zfs#2517 openzfs/zfs#2827 openzfs/zfs#2850 openzfs/zfs#2891 openzfs/zfs#2897 openzfs/zfs#2247 openzfs/zfs#2939 Signed-off-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Yao <ryao@gentoo.org> Closes #421
ryao
pushed a commit
to ryao/spl
that referenced
this issue
Feb 19, 2015
It is known that mutexes in Linux are not safe when using them to synchronize the freeing of object in which the mutex is embedded: http://lwn.net/Articles/575477/ The known places in ZFS which are suspected to suffer from the race condition are zio->io_lock and dbuf->db_mtx. * zio uses zio->io_lock and zio->io_cv to synchronize freeing between zio_wait() and zio_done(). * dbuf uses dbuf->db_mtx to protect reference counting. This patch fixes this kind of race by forcing serialization on mutex_exit() with a spin lock, making the mutex safe by sacrificing a bit of performance and memory overhead. This issue most commonly manifests itself as a deadlock in the zio pipeline caused by a process spinning on the damaged mutex. Similar deadlocks have been reported for the dbuf->db_mtx mutex. And it can also cause a NULL dereference or bad paging request under the right circumstances. This issue any many like it are linked off the openzfs/zfs#2523 issue. Specifically this fix resolves at least the following outstanding issues: openzfs/zfs#401 openzfs/zfs#2523 openzfs/zfs#2679 openzfs/zfs#2684 openzfs/zfs#2704 openzfs/zfs#2708 openzfs/zfs#2517 openzfs/zfs#2827 openzfs/zfs#2850 openzfs/zfs#2891 openzfs/zfs#2897 openzfs/zfs#2247 openzfs/zfs#2939 Signed-off-by: Chunwei Chen <tuxoko@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Richard Yao <ryao@gentoo.org> Closes openzfs#421 Conflicts: include/sys/mutex.h
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I hit this kernel oops last night. This was running latest as of 2014-09-09 on a 3.16.2 kernel.
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