Re: [PATCHSET v5] blk-mq: reimplement timeout handling
From: Ming Lei
Date: Sat Jan 13 2018 - 09:45:54 EST
On Fri, Jan 12, 2018 at 04:55:34PM -0500, Laurence Oberman wrote:
> On Fri, 2018-01-12 at 20:57 +0000, Bart Van Assche wrote:
> > On Tue, 2018-01-09 at 08:29 -0800, Tejun Heo wrote:
> > > Currently, blk-mq timeout path synchronizes against the usual
> > > issue/completion path using a complex scheme involving atomic
> > > bitflags, REQ_ATOM_*, memory barriers and subtle memory coherence
> > > rules. Unfortunatley, it contains quite a few holes.
> >
> > Hello Tejun,
> >
> > With this patch series applied I see weird hangs in blk_mq_get_tag()
> > when I
> > run the srp-test software. If I pull Jens' latest for-next branch and
> > revert
> > this patch series then the srp-test software runs successfully. Note:
> > if you
> > don't have InfiniBand hardware available then you will need the
> > RDMA/CM
> > patches for the SRP initiator and target drivers that have been
> > posted
> > recently on the linux-rdma mailing list to run the srp-test software.
> >
> > This is how I run the srp-test software in a VM:
> >
> > ./run_tests -c -d -r 10
> >
> > Here is an example of what SysRq-w reported when the hang occurred:
> >
> > sysrq: SysRq : Show Blocked State
> > task PC stack pid father
> > kworker/u8:0 D12864 5 2 0x80000000
> > Workqueue: events_unbound sd_probe_async [sd_mod]
> > Call Trace:
> > ? __schedule+0x2b4/0xbb0
> > schedule+0x2d/0x90
> > io_schedule+0xd/0x30
> > blk_mq_get_tag+0x169/0x290
> > ? finish_wait+0x80/0x80
> > blk_mq_get_request+0x16a/0x4f0
> > blk_mq_alloc_request+0x59/0xc0
> > blk_get_request_flags+0x3f/0x260
> > scsi_execute+0x33/0x1e0 [scsi_mod]
> > read_capacity_16.part.35+0x9c/0x460 [sd_mod]
> > sd_revalidate_disk+0x14bb/0x1cb0 [sd_mod]
> > sd_probe_async+0xf2/0x1a0 [sd_mod]
> > process_one_work+0x21c/0x6d0
> > worker_thread+0x35/0x380
> > ? process_one_work+0x6d0/0x6d0
> > kthread+0x117/0x130
> > ? kthread_create_worker_on_cpu+0x40/0x40
> > ret_from_fork+0x24/0x30
> > systemd-udevd D13672 1048 285 0x00000100
> > Call Trace:
> > ? __schedule+0x2b4/0xbb0
> > schedule+0x2d/0x90
> > io_schedule+0xd/0x30
> > generic_file_read_iter+0x32f/0x970
> > ? page_cache_tree_insert+0x100/0x100
> > __vfs_read+0xcc/0x120
> > vfs_read+0x96/0x140
> > SyS_read+0x40/0xa0
> > do_syscall_64+0x5f/0x1b0
> > entry_SYSCALL64_slow_path+0x25/0x25
> > RIP: 0033:0x7f8ce6d08d11
> > RSP: 002b:00007fff96dec288 EFLAGS: 00000246 ORIG_RAX:
> > 0000000000000000
> > RAX: ffffffffffffffda RBX: 00005651de7f6e10 RCX: 00007f8ce6d08d11
> > RDX: 0000000000000040 RSI: 00005651de7f6e38 RDI: 0000000000000007
> > RBP: 00005651de7ea500 R08: 00007f8ce6cf1c20 R09: 00005651de7f6e10
> > R10: 000000000000006f R11: 0000000000000246 R12: 0000000001ff0000
> > R13: 0000000001ff0040 R14: 00005651de7ea550 R15: 0000000000000040
> > systemd-udevd D13496 1049 285 0x00000100
> > Call Trace:
> > ? __schedule+0x2b4/0xbb0
> > schedule+0x2d/0x90
> > io_schedule+0xd/0x30
> > blk_mq_get_tag+0x169/0x290
> > ? finish_wait+0x80/0x80
> > blk_mq_get_request+0x16a/0x4f0
> > blk_mq_make_request+0x105/0x8e0
> > ? generic_make_request+0xd6/0x3d0
> > generic_make_request+0x103/0x3d0
> > ? submit_bio+0x57/0x110
> > submit_bio+0x57/0x110
> > mpage_readpages+0x13b/0x160
> > ? I_BDEV+0x10/0x10
> > ? rcu_read_lock_sched_held+0x66/0x70
> > ? __alloc_pages_nodemask+0x2e8/0x360
> > __do_page_cache_readahead+0x2a4/0x370
> > ? force_page_cache_readahead+0xaf/0x110
> > force_page_cache_readahead+0xaf/0x110
> > generic_file_read_iter+0x743/0x970
> > ? find_held_lock+0x2d/0x90
> > ? _raw_spin_unlock+0x29/0x40
> > __vfs_read+0xcc/0x120
> > vfs_read+0x96/0x140
> > SyS_read+0x40/0xa0
> > do_syscall_64+0x5f/0x1b0
> > entry_SYSCALL64_slow_path+0x25/0x25
> > RIP: 0033:0x7f8ce6d08d11
> > RSP: 002b:00007fff96dec8b8 EFLAGS: 00000246 ORIG_RAX:
> > 0000000000000000
> > RAX: ffffffffffffffda RBX: 00007f8ce7085010 RCX: 00007f8ce6d08d11
> > RDX: 0000000000040000 RSI: 00007f8ce7085038 RDI: 000000000000000f
> > RBP: 00005651de7ec840 R08: ffffffffffffffff R09: 00007f8ce7085010
> > R10: 00007f8ce7085028 R11: 0000000000000246 R12: 0000000000000000
> > R13: 0000000000040000 R14: 00005651de7ec890 R15: 0000000000040000
> > systemd-udevd D13672 1055 285 0x00000100
> > Call Trace:
> > ? __schedule+0x2b4/0xbb0
> > schedule+0x2d/0x90
> > io_schedule+0xd/0x30
> > blk_mq_get_tag+0x169/0x290
> > ? finish_wait+0x80/0x80
> > blk_mq_get_request+0x16a/0x4f0
> > blk_mq_make_request+0x105/0x8e0
> > ? generic_make_request+0xd6/0x3d0
> > generic_make_request+0x103/0x3d0
> > ? submit_bio+0x57/0x110
> > submit_bio+0x57/0x110
> > mpage_readpages+0x13b/0x160
> > ? I_BDEV+0x10/0x10
> > ? rcu_read_lock_sched_held+0x66/0x70
> > ? __alloc_pages_nodemask+0x2e8/0x360
> > __do_page_cache_readahead+0x2a4/0x370
> > ? force_page_cache_readahead+0xaf/0x110
> > force_page_cache_readahead+0xaf/0x110
> > generic_file_read_iter+0x743/0x970
> > __vfs_read+0xcc/0x120
> > vfs_read+0x96/0x140
> > SyS_read+0x40/0xa0
> > do_syscall_64+0x5f/0x1b0
> > entry_SYSCALL64_slow_path+0x25/0x25
> > RIP: 0033:0x7f8ce6d08d11
> > RSP: 002b:00007fff96dec848 EFLAGS: 00000246 ORIG_RAX:
> > 0000000000000000
> > RAX: ffffffffffffffda RBX: 00005651de7ec300 RCX: 00007f8ce6d08d11
> > RDX: 0000000000000100 RSI: 00005651de7ec328 RDI: 000000000000000f
> > RBP: 00005651de7ea500 R08: 0000000000000000 R09: 00005651de7ec300
> > R10: 00005651de7ec318 R11: 0000000000000246 R12: 0000000001ffe000
> > R13: 0000000001ffe100 R14: 00005651de7ea550 R15: 0000000000000100
> >
> > Please let me know if you need more information.
> >
> > Bart.
>
> I just bumped into stalls too, using Mike's tree. I had started getting
> ready with blk-mq enabled for both dm_mod and scsi_mod and testing SRP
> so I could run further tests for Bart.
>
> I am working to see when it started by starting first with Linus's
> latest tree as I tested that same without blk-mq initially and it was
> fine.
>
> My concern is that I tried a 4.15-rc1 kernel as well and still saw
> issues so have to sanitize all of this first and report back.
>
> My trace was this
>
> [ 615.714199] Tainted: G I 4.15.0-rc4+ #1
> [ 615.746226] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
> [ 615.790597] systemd-udevd D 0 2247 745 0x80000086
> [ 615.821048] Call Trace:
> [ 615.833971] ? __schedule+0x28d/0x870
> [ 615.854226] schedule+0x32/0x80
> [ 615.871819] io_schedule+0x12/0x40
> [ 615.890850] __lock_page+0x105/0x150
> [ 615.910378] ? page_cache_tree_insert+0xd0/0xd0
> [ 615.935932] truncate_inode_pages_range+0x49d/0x810
> [ 615.963371] __blkdev_put+0x73/0x200
> [ 615.983351] blkdev_close+0x21/0x30
> [ 616.002910] __fput+0xd5/0x210
> [ 616.019812] task_work_run+0x82/0xa0
> [ 616.040506] do_exit+0x2ce/0xb30
> [ 616.058622] do_group_exit+0x39/0xa0
> [ 616.079506] get_signal+0x1d0/0x5b0
> [ 616.100116] do_signal+0x36/0x610
> [ 616.118889] ? page_cache_tree_insert+0xd0/0xd0
> [ 616.144958] exit_to_usermode_loop+0x47/0x93
> [ 616.169040] do_syscall_64+0x172/0x1a0
> [ 616.190514] entry_SYSCALL64_slow_path+0x25/0x25
> [ 616.216566] RIP: 0033:0x7fb247dd86f0
> [ 616.237395] RSP: 002b:00007ffea3c56cb8 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000000
> [ 616.279551] RAX: fffffffffffffffc RBX: 0000000000200000 RCX:
> 00007fb247dd86f0
> [ 616.318057] RDX: 0000000000000400 RSI: 000055855eeefea8 RDI:
> 0000000000000008
> [ 616.357320] RBP: 000055855eeefe80 R08: 0000000005231994 R09:
> 0000000000000428
> [ 616.397099] R10: 0000000000000040 R11: 0000000000000246 R12:
> 000055855eeea550
> [ 616.436999] R13: 0000000000000400 R14: 000055855eeea5a0 R15:
> 000055855eeefe98
> [ 616.477831] INFO: task systemd-udevd:2248 blocked for more than 120
> seconds.
> [ 616.518289] Tainted: G I 4.15.0-rc4+ #1
> [ 616.549323] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
> disables this message.
I can trigger this hang too, looks it happens after starting multipathd,
and 'lsblk' also complains:
lsblk: dm-0: failed to get device path
lsblk: dm-0: failed to get device path
And one SCSI device can't be attached to dm-mpath.
But it may not be related with IO, since when this hang happens,
there isn't any pending IO observed from blk-mq debugfs.
I also tries Jan's 6 patches for fixing race between bdev open and
gendisk shutdown, and looks they can't help the issue.
https://marc.info/?l=linux-block&m=151569001430678&w=2
Thanks,
Ming