On Mon, Aug 30 2010 at 3:08pm -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > On Mon, Aug 30 2010 at 11:07am -0400, > Tejun Heo <tj@xxxxxxxxxx> wrote: > > > On 08/30/2010 03:59 PM, Tejun Heo wrote: > > > Ah... that's probably from "if (!elv_queue_empty(q))" check below, > > > flushes are on a separate queue but I forgot to update > > > elv_queue_empty() to check the flush queue. elv_queue_empty() can > > > return %true spuriously in which case the queue won't be plugged and > > > restarted later leading to queue hang. I'll fix elv_queue_empty(). > > > > I think I was too quick to blame elv_queue_empty(). Can you please > > test whether the following patch fixes the hang? > > It does, thanks! Hmm, but unfortunately I was too quick to say the patch fixed the hang. It is much more rare, but I can still get a hang. I just got the following running vgcreate against an DM mpath (rq-based) device: INFO: task vgcreate:3517 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. vgcreate D ffff88003d677a00 5168 3517 3361 0x00000080 ffff88003d677998 0000000000000046 ffff880000000000 ffff88003d677fd8 ffff880039c84860 ffff88003d677fd8 00000000001d3880 ffff880039c84c30 ffff880039c84c28 00000000001d3880 00000000001d3880 ffff88003d677fd8 Call Trace: [<ffffffff81389308>] io_schedule+0x73/0xb5 [<ffffffff811c7304>] get_request_wait+0xef/0x17d [<ffffffff810642be>] ? autoremove_wake_function+0x0/0x39 [<ffffffff811c7890>] __make_request+0x333/0x467 [<ffffffff810251e5>] ? pvclock_clocksource_read+0x50/0xb9 [<ffffffff811c5e91>] generic_make_request+0x342/0x3bf [<ffffffff81074714>] ? trace_hardirqs_off+0xd/0xf [<ffffffff81069df2>] ? local_clock+0x41/0x5a [<ffffffff811c5fe9>] submit_bio+0xdb/0xf8 [<ffffffff810754a4>] ? trace_hardirqs_on+0xd/0xf [<ffffffff811381a6>] dio_bio_submit+0x7b/0x9c [<ffffffff81138dbe>] __blockdev_direct_IO+0x7f3/0x97d [<ffffffff810251e5>] ? pvclock_clocksource_read+0x50/0xb9 [<ffffffff81136d7a>] blkdev_direct_IO+0x57/0x59 [<ffffffff81135f58>] ? blkdev_get_blocks+0x0/0x90 [<ffffffff810ce301>] generic_file_aio_read+0xed/0x5b4 [<ffffffff81077932>] ? lock_release_non_nested+0xd5/0x23b [<ffffffff810e40f8>] ? might_fault+0x5c/0xac [<ffffffff810251e5>] ? pvclock_clocksource_read+0x50/0xb9 [<ffffffff8110e131>] do_sync_read+0xcb/0x108 [<ffffffff81074688>] ? trace_hardirqs_off_caller+0x1f/0x9e [<ffffffff81389a99>] ? __mutex_unlock_slowpath+0x120/0x132 [<ffffffff8119d805>] ? fsnotify_perm+0x4a/0x50 [<ffffffff8119d86c>] ? security_file_permission+0x2e/0x33 [<ffffffff8110e7a3>] vfs_read+0xab/0x107 [<ffffffff81075473>] ? trace_hardirqs_on_caller+0x11d/0x141 [<ffffffff8110e8c2>] sys_read+0x4d/0x74 [<ffffffff81002c32>] system_call_fastpath+0x16/0x1b no locks held by vgcreate/3517. I was then able to reproduce it after reboot and another ~5 attempts (all against 2.6.36-rc2 + your latest FLUSH+FUA patchset and DM patches). crash> bt -l 3893 PID: 3893 TASK: ffff88003e65a430 CPU: 0 COMMAND: "vgcreate" #0 [ffff88003a5298d8] schedule at ffffffff813891d3 /root/git/linux-2.6/kernel/sched.c: 2873 #1 [ffff88003a5299a0] io_schedule at ffffffff81389308 /root/git/linux-2.6/kernel/sched.c: 5128 #2 [ffff88003a5299c0] get_request_wait at ffffffff811c7304 /root/git/linux-2.6/block/blk-core.c: 879 #3 [ffff88003a529a50] __make_request at ffffffff811c7890 /root/git/linux-2.6/block/blk-core.c: 1301 #4 [ffff88003a529ac0] generic_make_request at ffffffff811c5e91 /root/git/linux-2.6/block/blk-core.c: 1536 #5 [ffff88003a529b70] submit_bio at ffffffff811c5fe9 /root/git/linux-2.6/block/blk-core.c: 1632 #6 [ffff88003a529bc0] dio_bio_submit at ffffffff811381a6 /root/git/linux-2.6/fs/direct-io.c: 375 #7 [ffff88003a529bf0] __blockdev_direct_IO at ffffffff81138dbe /root/git/linux-2.6/fs/direct-io.c: 1087 #8 [ffff88003a529cd0] blkdev_direct_IO at ffffffff81136d7a /root/git/linux-2.6/fs/block_dev.c: 177 #9 [ffff88003a529d10] generic_file_aio_read at ffffffff810ce301 /root/git/linux-2.6/mm/filemap.c: 1303 #10 [ffff88003a529df0] do_sync_read at ffffffff8110e131 /root/git/linux-2.6/fs/read_write.c: 282 #11 [ffff88003a529f00] vfs_read at ffffffff8110e7a3 /root/git/linux-2.6/fs/read_write.c: 310 #12 [ffff88003a529f40] sys_read at ffffffff8110e8c2 /root/git/linux-2.6/fs/read_write.c: 388 #13 [ffff88003a529f80] system_call_fastpath at ffffffff81002c32 /root/git/linux-2.6/arch/x86/kernel/entry_64.S: 488 RIP: 0000003b602d41a0 RSP: 00007fff55d5b928 RFLAGS: 00010246 RAX: 0000000000000000 RBX: ffffffff81002c32 RCX: 00007fff55d5b960 RDX: 0000000000001000 RSI: 00007fff55d5a000 RDI: 0000000000000005 RBP: 0000000000000000 R8: 0000000000494ecd R9: 0000000000001000 R10: 000000315c41c160 R11: 0000000000000246 R12: 00007fff55d5a000 R13: 00007fff55d5b0a0 R14: 0000000000000000 R15: 0000000000000000 ORIG_RAX: 0000000000000000 CS: 0033 SS: 002b -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel