On 09/10/2013 03:58 PM, Jeff Liu wrote: > On 09/10/2013 03:36 PM, Dave Chinner wrote: > >> FOlks, >> >> I just got confirmation of a deadlock I suspected has existed for >> some time. A concurrent 16-way create and 16-way unlink just locked >> up with two threads looking like this: >> >> fs_mark D ffff88021bd931c0 3656 7204 7117 0x00000000 >> ffff8801e75293a8 0000000000000086 ffff88012c6d0000 ffff8801e7529fd8 >> ffff8801e7529fd8 ffff8801e7529fd8 ffff8802d32aae40 ffff88012c6d0000 >> ffff8801a2f79d40 7fffffffffffffff ffff8801ee733bb0 0000000000000002 >> Call Trace: >> [<ffffffff819b0d19>] schedule+0x29/0x70 >> [<ffffffff819acd09>] schedule_timeout+0x149/0x1f0 >> [<ffffffff819af6bc>] __down_common+0x91/0xe8 >> [<ffffffff819af786>] __down+0x1d/0x1f >> [<ffffffff810b5211>] down+0x41/0x50 >> [<ffffffff81423dd0>] xfs_buf_lock+0x40/0xf0 >> [<ffffffff81424051>] _xfs_buf_find+0x1d1/0x4d0 >> [<ffffffff814244f5>] xfs_buf_get_map+0x35/0x180 >> [<ffffffff81425517>] xfs_buf_read_map+0x37/0x110 >> [<ffffffff8149e299>] xfs_trans_read_buf_map+0x379/0x600 >> [<ffffffff81444178>] xfs_read_agf+0xa8/0x100 >> [<ffffffff8144423a>] xfs_alloc_read_agf+0x6a/0x250 >> [<ffffffff81444950>] xfs_alloc_fix_freelist+0x4f0/0x5a0 >> [<ffffffff81444e40>] xfs_alloc_vextent+0x440/0x840 >> [<ffffffff8147d0cf>] xfs_ialloc_ag_alloc+0x13f/0x520 >> [<ffffffff8147e871>] xfs_dialloc+0x121/0x2d0 >> [<ffffffff814803db>] xfs_ialloc+0x5b/0x7c0 >> [<ffffffff81480bda>] xfs_dir_ialloc+0x9a/0x2f0 >> [<ffffffff8148134d>] xfs_create+0x47d/0x6a0 >> [<ffffffff814343ea>] xfs_vn_mknod+0xba/0x1c0 >> [<ffffffff81434523>] xfs_vn_create+0x13/0x20 >> [<ffffffff811a62a5>] vfs_create+0xb5/0xf0 >> [<ffffffff811a6a40>] do_last.isra.56+0x760/0xd10 >> [<ffffffff811a70ae>] path_openat+0xbe/0x620 >> [<ffffffff811a7bc3>] do_filp_open+0x43/0xa0 >> [<ffffffff811969cc>] do_sys_open+0x13c/0x230 >> [<ffffffff81196ae2>] SyS_open+0x22/0x30 >> [<ffffffff819bae19>] system_call_fastpath+0x16/0x1b >> >> That a thread holding an AGI and blocking trying to get the AGF to >> do an inode chunk allocation. >> >> rm D ffff88021bd931c0 3048 7073 7063 0x00000000 >> ffff8802bc66d998 0000000000000086 ffff8802d32aae40 ffff8802bc66dfd8 >> ffff8802bc66dfd8 ffff8802bc66dfd8 ffff88012c6d5c80 ffff8802d32aae40 >> ffff8804091b2b00 7fffffffffffffff ffff8801b943c570 0000000000000002 >> Call Trace: >> [<ffffffff819b0d19>] schedule+0x29/0x70 >> [<ffffffff819acd09>] schedule_timeout+0x149/0x1f0 >> [<ffffffff819af6bc>] __down_common+0x91/0xe8 >> [<ffffffff819af786>] __down+0x1d/0x1f >> [<ffffffff810b5211>] down+0x41/0x50 >> [<ffffffff81423dd0>] xfs_buf_lock+0x40/0xf0 >> [<ffffffff81424051>] _xfs_buf_find+0x1d1/0x4d0 >> [<ffffffff814244f5>] xfs_buf_get_map+0x35/0x180 >> [<ffffffff81425517>] xfs_buf_read_map+0x37/0x110 >> [<ffffffff8149e299>] xfs_trans_read_buf_map+0x379/0x600 >> [<ffffffff8147d8ca>] xfs_read_agi+0xaa/0x100 >> [<ffffffff81481f4e>] xfs_iunlink+0x8e/0x260 >> [<ffffffff81482198>] xfs_droplink+0x78/0x80 >> [<ffffffff81483671>] xfs_remove+0x331/0x420 >> [<ffffffff814340f2>] xfs_vn_unlink+0x52/0xa0 >> [<ffffffff811a4f9e>] vfs_unlink+0x9e/0x110 >> [<ffffffff811a51b1>] do_unlinkat+0x1a1/0x230 >> [<ffffffff811a805b>] SyS_unlinkat+0x1b/0x40 >> >> And that's a thread that has just freed a directory block and so >> holds an AGF lock, and is trying to take the AGI lock to add the >> inode to the unlinked list. Everything else is now stuck waiting >> for log space because one of the two buffers we've deadlocked on >> here pins the tail of the log. >> >> The solution is to place the inode on the unlinked list before we >> remove the directory entry so that we keep the same locking order as >> inode allocation. >> >> I don't have time to look at this for at least a week, so if someone >> could work up solution that'd be wonderful... > > Although I can reproduce it for now, but it looks interesting to me. Sorry, s/can/can not/. > I'll take care of this problem. Still no luck to reproduce it on my poor laptop, so I have to release this for someone who can reproduce it and be interesting enough in fix it. :) Thanks, -Jeff _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
