linux-kernel - Re: [PATCH -tip/core/rcu 1/6] Cleanups and fixes for RCU in face of heavy CPU-hotplug stress

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Message-ID: <20090818152643.GA5549@elte.hu>
Date:	Tue, 18 Aug 2009 17:26:43 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Josh Triplett <josht@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
	hugh.dickins@...cali.co.uk, benh@...nel.crashing.org
Subject: Re: [PATCH -tip/core/rcu 1/6] Cleanups and fixes for RCU in face
	of heavy CPU-hotplug stress


FYI, i've started triggering hangs in -tip testing recently, during 
CPU hotplug tests:

[   57.632003] eth0: no IPv6 routers present
[  103.564010] kmemleak: 29 new suspected memory leaks (see /sys/kernel/debug/kmemleak)
[  200.380003] Hangcheck: hangcheck value past margin!
[  248.192003] INFO: task S99local:2974 blocked for more than 120 seconds.
[  248.194532] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  248.202330] S99local      D 0000000c  6256  2974   2687 0x00000000
[  248.208929]  9c7ebe90 00000086 6b67ef8b 0000000c 9f25a610 81a69869 00000001 820b6990
[  248.216123]  820b6990 820b6990 9c6e4c20 9c6e4eb4 82c78990 00000000 6b993559 0000000c
[  248.220616]  9c7ebe90 8105f22a 9c6e4eb4 9c6e4c20 00000001 9c7ebe98 9c7ebeb4 81a65cb3
[  248.229990] Call Trace:
[  248.234049]  [<81a69869>] ? _spin_unlock_irqrestore+0x22/0x37
[  248.239769]  [<8105f22a>] ? prepare_to_wait+0x48/0x4e
[  248.244796]  [<81a65cb3>] rcu_barrier_cpu_hotplug+0xaa/0xc9
[  248.250343]  [<8105f029>] ? autoremove_wake_function+0x0/0x38
[  248.256063]  [<81062cf2>] notifier_call_chain+0x49/0x71
[  248.261263]  [<81062da0>] raw_notifier_call_chain+0x11/0x13
[  248.266809]  [<81a0b475>] _cpu_down+0x272/0x288
[  248.271316]  [<81a0b4d5>] cpu_down+0x4a/0xa2
[  248.275563]  [<81a0c48a>] store_online+0x2a/0x5e
[  248.280156]  [<81a0c460>] ? store_online+0x0/0x5e
[  248.284836]  [<814ddc35>] sysdev_store+0x20/0x28
[  248.289429]  [<8112e403>] sysfs_write_file+0xb8/0xe3
[  248.294369]  [<8112e34b>] ? sysfs_write_file+0x0/0xe3
[  248.299396]  [<810e4c8f>] vfs_write+0x91/0x120
[  248.303817]  [<810e4dc1>] sys_write+0x40/0x65
[  248.308150]  [<81002d73>] sysenter_do_call+0x12/0x28

config and bootlog attached. I'd suspect one of these patches:

684ca5c: rcu: Fix typo in rcu_irq_exit() comment header
b612ba8: rcu: Make rcupreempt_trace.c look at offline CPUs
8064d54: rcu: Make preemptable RCU scan all CPUs when summing RCU counters
2e59755: rcu: Simplify RCU CPU-hotplug notification
799e64f: cpu hotplug: Introduce cpu_notifier() to handle !HOTPLUG_CPU case
2756962: rcu: Split hierarchical RCU initialization into boot-time and CPU-online piece

Any ideas?

	Ingo

View attachment "config" of type "text/plain" (72661 bytes)

View attachment "hang.log" of type "text/plain" (448900 bytes)