From: Peter Zijlstra <peterz@infradead.org>
To: Ed Tomlinson <edt@aei.ca>
Cc: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
patches@linaro.org, greearb@candelatech.com
Subject: Re: [PATCH tip/core/urgent 1/7] rcu: decrease rcu_report_exp_rnp coupling with scheduler
Date: Wed, 20 Jul 2011 14:35:20 +0200 [thread overview]
Message-ID: <1311165320.5345.77.camel@twins> (raw)
In-Reply-To: <201107200723.33819.edt@aei.ca>
On Wed, 2011-07-20 at 07:23 -0400, Ed Tomlinson wrote:
> [ 3.553004] [<ffffffff8104b06a>] warn_slowpath_null+0x1a/0x20
> [ 3.553004] [<ffffffff810bb479>] __rcu_read_unlock+0xc9/0x120
> [ 3.553004] [<ffffffff8103fed8>] cpuacct_charge+0xc8/0xe0
> [ 3.553004] [<ffffffff8103fe58>] ? cpuacct_charge+0x48/0xe0
> [ 3.553004] [<ffffffff810326b7>] ? task_of+0x97/0xd0
> [ 3.553004] [<ffffffff81040ef5>] update_curr+0x1a5/0x210
> [ 3.553004] [<ffffffff81576d78>] ? preempt_schedule_irq+0x68/0xa0
> [ 3.553004] [<ffffffff810419e0>] put_prev_task_fair+0x110/0x120
> [ 3.553004] [<ffffffff81575f3a>] schedule+0x1da/0xc50
> [ 3.553004] [<ffffffff81576d72>] ? preempt_schedule_irq+0x62/0xa0
> [ 3.553004] [<ffffffff81576d78>] preempt_schedule_irq+0x68/0xa0
> [ 3.553004] [<ffffffff8157a316>] retint_kernel+0x26/0x30
> [ 3.553004] [<ffffffff810da494>] ? ftrace_likely_update+0x14/0x20
> [ 3.553004] [<ffffffff810bb4ab>] __rcu_read_unlock+0xfb/0x120
> [ 3.553004] [<ffffffff810f8190>] find_get_page+0x170/0x190
Ok, so we're running some task that does rcu_read_unlock(), right in the
middle of __rcu_read_unlock() we get preempted, the scheduler calls
rcu_note_context_switch()->rcu_preempt_note_context_switch() which sets
->rcu_read_unlock_special |= UNLOCK_BLOCKED.
Then before finishing the context switch, the cpuacct muck uses rcu, and
its rcu_read_unlock() triggers __rcu_read_unlock() and goes bang.
That rcu usage isn't new, that's been there since March 2009.
AFAICT even .39 should suffer from this particular issue, or am I
missing something here.. Paul?
next prev parent reply other threads:[~2011-07-20 12:36 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-20 0:17 [PATCH rcu/urgent 0/6] Fixes for RCU/scheduler/irq-threads trainwreck Paul E. McKenney
2011-07-20 0:18 ` [PATCH tip/core/urgent 1/7] rcu: decrease rcu_report_exp_rnp coupling with scheduler Paul E. McKenney
2011-07-20 2:40 ` Peter Zijlstra
2011-07-20 4:54 ` Paul E. McKenney
2011-07-20 11:23 ` Ed Tomlinson
2011-07-20 11:31 ` Ed Tomlinson
2011-07-20 12:35 ` Peter Zijlstra [this message]
2011-07-20 13:23 ` Paul E. McKenney
2011-07-20 0:18 ` [PATCH tip/core/urgent 2/7] rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special Paul E. McKenney
2011-07-20 0:18 ` [PATCH tip/core/urgent 3/7] rcu: Streamline code produced by __rcu_read_unlock() Paul E. McKenney
2011-07-20 0:18 ` [PATCH tip/core/urgent 4/7] rcu: protect __rcu_read_unlock() against scheduler-using irq handlers Paul E. McKenney
2011-07-20 12:54 ` Peter Zijlstra
2011-07-20 13:25 ` Paul E. McKenney
2011-07-20 0:18 ` [PATCH tip/core/urgent 5/7] sched: Add irq_{enter,exit}() to scheduler_ipi() Paul E. McKenney
2011-07-20 0:18 ` [PATCH tip/core/urgent 6/7] softirq,rcu: Inform RCU of irq_exit() activity Paul E. McKenney
2011-07-20 0:18 ` [PATCH tip/core/urgent 7/7] signal: align __lock_task_sighand() irq disabling and RCU Paul E. McKenney
2011-07-20 1:10 ` [PATCH rcu/urgent 0/6] Fixes for RCU/scheduler/irq-threads trainwreck Ben Greear
2011-07-20 1:30 ` Ed Tomlinson
2011-07-20 2:07 ` Ed Tomlinson
2011-07-20 4:44 ` Paul E. McKenney
2011-07-20 5:03 ` Linus Torvalds
2011-07-20 13:34 ` Paul E. McKenney
2011-07-20 17:02 ` Ben Greear
2011-07-20 17:15 ` Paul E. McKenney
2011-07-20 18:44 ` Ingo Molnar
2011-07-20 18:52 ` Peter Zijlstra
2011-07-20 19:01 ` Paul E. McKenney
2011-07-20 19:25 ` Peter Zijlstra
2011-07-20 20:06 ` Paul E. McKenney
2011-07-20 19:02 ` Linus Torvalds
2011-07-20 19:29 ` Paul E. McKenney
2011-07-20 19:39 ` Ingo Molnar
2011-07-20 19:57 ` Ingo Molnar
2011-07-20 20:33 ` Paul E. McKenney
2011-07-20 20:54 ` Ben Greear
2011-07-20 21:12 ` Paul E. McKenney
2011-07-21 3:25 ` Ben Greear
2011-07-21 16:04 ` Paul E. McKenney
2011-07-20 21:04 ` [GIT PULL] RCU fixes for v3.0 Ingo Molnar
2011-07-20 21:55 ` Ed Tomlinson
2011-07-20 22:06 ` Paul E. McKenney
2011-07-20 20:08 ` [PATCH rcu/urgent 0/6] Fixes for RCU/scheduler/irq-threads trainwreck Paul E. McKenney
2011-07-20 21:05 ` Peter Zijlstra
2011-07-20 21:39 ` Paul E. McKenney
2011-07-20 10:49 ` Ed Tomlinson
2011-07-20 18:25 ` [PATCH rcu/urgent 0/7 v2] " Paul E. McKenney
2011-07-20 18:26 ` [PATCH tip/core/urgent 1/7] rcu: decrease rcu_report_exp_rnp coupling with scheduler Paul E. McKenney
2011-07-20 18:26 ` [PATCH tip/core/urgent 2/7] rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special Paul E. McKenney
2011-07-20 18:26 ` [PATCH tip/core/urgent 3/7] rcu: Streamline code produced by __rcu_read_unlock() Paul E. McKenney
2011-07-20 22:44 ` Linus Torvalds
2011-07-21 5:09 ` Paul E. McKenney
2011-07-20 18:26 ` [PATCH tip/core/urgent 4/7] rcu: protect __rcu_read_unlock() against scheduler-using irq handlers Paul E. McKenney
2011-07-20 18:26 ` [PATCH tip/core/urgent 5/7] sched: Add irq_{enter,exit}() to scheduler_ipi() Paul E. McKenney
2011-07-20 18:26 ` [PATCH tip/core/urgent 6/7] softirq,rcu: Inform RCU of irq_exit() activity Paul E. McKenney
2011-07-20 18:26 ` [PATCH tip/core/urgent 7/7] signal: align __lock_task_sighand() irq disabling and RCU Paul E. McKenney
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