From b76b4014f9d988d2412b873e4d4c13c7f9afc4e4 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Sat, 28 Aug 2010 08:52:10 +0200 Subject: writeback: Fix lost wake-up shutting down writeback thread Setting the task state here may cause us to miss the wake up from kthread_stop(), so we need to recheck kthread_should_stop() or risk sleeping forever in the following schedule(). Symptom was an indefinite hang on an NFSv4 mount. (NFSv4 may create multiple mounts in a temporary namespace while traversing the mount path, and since the temporary namespace is immediately destroyed, it may end up destroying a mount very soon after it was created, possibly making this race more likely.) INFO: task mount.nfs4:4314 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. mount.nfs4 D 0000000000000000 2880 4314 4313 0x00000000 ffff88001ed6da28 0000000000000046 ffff88001ed6dfd8 ffff88001ed6dfd8 ffff88001ed6c000 ffff88001ed6c000 ffff88001ed6c000 ffff88001e5003a0 ffff88001ed6dfd8 ffff88001e5003a8 ffff88001ed6c000 ffff88001ed6dfd8 Call Trace: [] schedule_timeout+0x1cd/0x2e0 [] ? mark_held_locks+0x6c/0xa0 [] ? _raw_spin_unlock_irq+0x30/0x60 [] ? trace_hardirqs_on_caller+0x14d/0x190 [] ? sub_preempt_count+0xe/0xd0 [] wait_for_common+0x120/0x190 [] ? default_wake_function+0x0/0x20 [] wait_for_completion+0x1d/0x20 [] kthread_stop+0x4a/0x150 [] ? thaw_process+0x70/0x80 [] bdi_unregister+0x10a/0x1a0 [] nfs_put_super+0x19/0x20 [] generic_shutdown_super+0x54/0xe0 [] kill_anon_super+0x16/0x60 [] nfs4_kill_super+0x39/0x90 [] deactivate_locked_super+0x45/0x60 [] deactivate_super+0x49/0x70 [] mntput_no_expire+0x84/0xe0 [] release_mounts+0x9f/0xc0 [] put_mnt_ns+0x65/0x80 [] nfs_follow_remote_path+0x1e6/0x420 [] nfs4_try_mount+0x6f/0xd0 [] nfs4_get_sb+0xa2/0x360 [] vfs_kern_mount+0x88/0x1f0 [] do_kern_mount+0x52/0x130 [] ? _lock_kernel+0x6a/0x170 [] do_mount+0x26e/0x7f0 [] ? copy_mount_options+0xea/0x190 [] sys_mount+0x98/0xf0 [] system_call_fastpath+0x16/0x1b 1 lock held by mount.nfs4/4314: #0: (&type->s_umount_key#24){+.+...}, at: [] deactivate_super+0x41/0x70 Signed-off-by: J. Bruce Fields Signed-off-by: Jens Axboe Acked-by: Artem Bityutskiy --- fs/fs-writeback.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 7d9d06ba184b..81e086d8aa57 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -808,7 +808,7 @@ int bdi_writeback_thread(void *data) wb->last_active = jiffies; set_current_state(TASK_INTERRUPTIBLE); - if (!list_empty(&bdi->work_list)) { + if (!list_empty(&bdi->work_list) || kthread_should_stop()) { __set_current_state(TASK_RUNNING); continue; } -- cgit v1.2.3