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Date: Wed, 29 Oct 2014 07:06:39 -0400
From: Theodore Ts'o <tytso@....edu>
To: linux-ext4@...r.kernel.org, linux-aio@...ck.org
cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Zach Brown <zab@...bo.net>, Benjamin LaHaise <bcrl@...ck.org>
Subject: RCU related deadlock in AIO? (in 3.18-rc2)
I have a vague memory of seeing discussion about a stack trace that
looks similar to this in the past few weeks. Does this ring a bell at
all?
The following hang happened while running xfstests generic/323 under
ext4 in no-journal mode, running on a 3.18-rc2 kernel. This is a
recently added test, to deal with a proble which I thought had already
been fixed in mainline.
# Run aio-last-ref-held-by-io - last put of ioctx not in process
# context. We've had a couple of instances in the past where having the
# last reference to an ioctx be held by the IO (instead of the
# process) would cause problems (hung system, crashes).
Thanks,
- Ted
generic/323 123s ... [06:42:18][30020.393779] ------------[ cut here ]------------
[30020.394962] WARNING: CPU: 1 PID: 0 at /usr/projects/linux/ext4/lib/percpu-refcount.c:151 percpu_ref_switch_to_atomic_rcu+0x9f/0xbc()
[30020.397073] percpu ref (free_ioctx_reqs) <= 0 (-65534) after switching to atomic
[30020.397073] Modules linked in:
[30020.397073] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.18.0-rc2-00005-gb790865 #2277
[30020.401678] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[30020.402522] 00000000 00000000 f553ff28 c088aba8 f553ff54 f553ff44 c0170af6 00000097
[30020.406004] c046cf41 df614874 ca3cd9f8 7fff0004 f553ff5c c0170b38 00000009 f553ff54
[30020.408552] c0b9dcf8 f553ff70 f553ff88 c046cf41 c0b9dc8d 00000097 c0b9dcf8 c028233d
[30020.410484] Call Trace:
[30020.410828] [<c088aba8>] dump_stack+0x48/0x60
[30020.411578] [<c0170af6>] warn_slowpath_common+0x6c/0x83
[30020.412701] [<c046cf41>] ? percpu_ref_switch_to_atomic_rcu+0x9f/0xbc
[30020.413541] [<c0170b38>] warn_slowpath_fmt+0x2b/0x2f
[30020.413715] [<c046cf41>] percpu_ref_switch_to_atomic_rcu+0x9f/0xbc
[30020.414267] [<c028233d>] ? rcu_lock_acquire+0x1c/0x1c
[30020.415101] [<c01b767b>] rcu_process_callbacks+0x2b5/0x433
[30020.415763] [<c01b767b>] ? rcu_process_callbacks+0x2b5/0x433
[30020.417024] [<c046cea2>] ? percpu_ref_reinit+0x50/0x50
[30020.417273] [<c0173f8f>] ? __local_bh_disable_ip+0x6e/0x6e
[30020.417959] [<c01740fc>] __do_softirq+0x16d/0x376
[30020.418688] [<c0173f8f>] ? __local_bh_disable_ip+0x6e/0x6e
[30020.419324] [<c01381ec>] do_softirq_own_stack+0x26/0x2c
[30020.420372] <IRQ> [<c01744f9>] irq_exit+0x42/0x8f
[30020.420796] [<c0137b94>] do_IRQ+0x89/0x9d
[30020.421606] [<c08943f1>] common_interrupt+0x31/0x38
[30020.422162] [<c013007b>] ? add_atomic_switch_msr+0x173/0x173
[30020.422850] [<c0164b9c>] ? native_safe_halt+0x5/0x7
[30020.423696] [<c013dee4>] default_idle+0x22/0x4b
[30020.424321] [<c013e49a>] arch_cpu_idle+0xe/0x10
[30020.424967] [<c019b7f0>] cpu_startup_entry+0x130/0x250
[30020.425604] [<c015a3a3>] start_secondary+0x15d/0x166
[30020.426333] ---[ end trace 4f7947d25059a4b4 ]---
[30240.260397] INFO: task aio-last-ref-he:9183 blocked for more than 120 seconds.[30240.261418] Tainted: G W 3.18.0-rc2-00005-gb790865 #2277
[30240.262399] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[30240.263575] d7e99e78 00000046 c0f6b280 c0f6b280 a9372026 00001b4d cdfc5800 00001b4d
[30240.264979] d9758350 f6250880 d7e99e60 c0192666 000396f0 00000000 a9371bab 00001b4d
[30240.266194] a9371cc6 00001b4d a9371bab 00001b4d d97588c4 c0f6b880 00000001 d7e99e8c
[30240.267449] Call Trace:
[30240.267795] [<c0192666>] ? sched_clock_local+0x10/0x10e
[30240.268515] [<c019298f>] ? sched_clock_cpu+0xd1/0xec
[30240.269207] [<c0192666>] ? sched_clock_local+0x10/0x10e
[30240.269929] [<c088fdaf>] schedule+0x5a/0x5c
[30240.270530] [<c0892b2b>] schedule_timeout+0x1a/0x9c
[30240.271245] [<c01929f4>] ? local_clock+0x18/0x22
[30240.271890] [<c01a0085>] ? lock_release_holdtime.part.25+0x60/0x6d
[30240.272736] [<c089343b>] ? _raw_spin_unlock_irq+0x27/0x36
[30240.273480] [<c01a1a20>] ? trace_hardirqs_on_caller+0x15f/0x17a
[30240.274329] [<c01a1a46>] ? trace_hardirqs_on+0xb/0xd
[30240.275054] [<c0893440>] ? _raw_spin_unlock_irq+0x2c/0x36
[30240.275798] [<c0890584>] __wait_for_common+0xcb/0xf5
[30240.276485] [<c0892b11>] ? console_conditional_schedule+0x29/0x29
[30240.277343] [<c01909aa>] ? wake_up_state+0x11/0x11
[30240.278016] [<c08905c7>] wait_for_completion+0x19/0x1c
[30240.278727] [<c0282f60>] SYSC_io_destroy+0x7a/0xaf
[30240.279409] [<c08904ea>] ? __wait_for_common+0x31/0xf5
[30240.280116] [<c02837dc>] SyS_io_destroy+0x10/0x12
[30240.280815] [<c046895a>] ? trace_hardirqs_on_thunk+0xc/0x10
[30240.281583] [<c02837dc>] ? SyS_io_destroy+0x10/0x12
[30240.282271] [<c0893e2a>] syscall_call+0x7/0x7
[30240.282881] [<c0890000>] ? schedule_preempt_disabled+0xd/0x1d
[30240.283692] no locks held by aio-last-ref-he/9183.
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