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a3c1eb7772
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 zfsonlinux/zfs#2523 issue. Specifically this fix resolves at least the following outstanding issues: zfsonlinux/zfs#401 zfsonlinux/zfs#2523 zfsonlinux/zfs#2679 zfsonlinux/zfs#2684 zfsonlinux/zfs#2704 zfsonlinux/zfs#2708 zfsonlinux/zfs#2517 zfsonlinux/zfs#2827 zfsonlinux/zfs#2850 zfsonlinux/zfs#2891 zfsonlinux/zfs#2897 zfsonlinux/zfs#2247 zfsonlinux/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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| Makefile.am | ||
| spl-ctl.h | ||
| splat-ctl.h | ||
| strings.h | ||
| unistd.h | ||