From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>, Dave Jones <davej@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Serge Hallyn <serge.hallyn@canonical.com>,
linux-kernel@vger.kernel.org
Subject: Re: lots of suspicious RCU traces
Date: Wed, 24 Oct 2012 22:55:31 -0700 [thread overview]
Message-ID: <20121025055531.GB2661@swordfish> (raw)
In-Reply-To: <CAFTL4hxmh7yV8ePUhY_7hOuG=JrbZZcNvV88bWcUmwG9X0W04A@mail.gmail.com>
On (10/25/12 00:32), Frederic Weisbecker wrote:
> > My understanding is (I may be wrong) that we can schedule() from ptrace chain to
> > some arbitrary task, which will continue its execution from the point where RCU assumes
> > CPU as not idle, while CPU in fact still in idle state -- no one said rcu_idle_exit()
> > (or similar) prior to schedule() call.
>
> Yeah but when we are in syscall_trace_leave(), the CPU shouldn't be in
> RCU idle mode. That's where the bug is. How do you manage to trigger
> this bug?
>
just for note,
git bisect good v3.6
[ 199.897703] ===============================
[ 199.897706] [ INFO: suspicious RCU usage. ]
[ 199.897710] 3.6.0-dbg-06307-ga78562e-dirty #1379 Not tainted
[ 199.897713] -------------------------------
[ 199.897717] include/linux/rcupdate.h:738 rcu_read_lock() used illegally while idle!
[ 199.897719]
other info that might help us debug this:
[ 199.897724]
RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 1
[ 199.897729] RCU used illegally from extended quiescent state!
[ 199.897732] 2 locks held by top/2396:
[ 199.897735] #0: (&rq->lock){-.-.-.}, at: [<ffffffff815c7ae9>] __schedule+0x119/0xb10
[ 199.897755] #1: (rcu_read_lock){.+.+..}, at: [<ffffffff81081f25>] cpuacct_charge+0x15/0x250
[ 199.897770]
stack backtrace:
[ 199.897775] Pid: 2396, comm: top Not tainted 3.6.0-dbg-06307-ga78562e-dirty #1379
[ 199.897779] Call Trace:
[ 199.897791] [<ffffffff810a7ed2>] lockdep_rcu_suspicious+0xe2/0x130
[ 199.897798] [<ffffffff810820cc>] cpuacct_charge+0x1bc/0x250
[ 199.897804] [<ffffffff81081f25>] ? cpuacct_charge+0x15/0x250
[ 199.897810] [<ffffffff815c7ae9>] ? __schedule+0x119/0xb10
[ 199.897818] [<ffffffff8108567c>] update_curr+0xec/0x230
[ 199.897825] [<ffffffff8108653c>] put_prev_task_fair+0x9c/0xf0
[ 199.897831] [<ffffffff815c7b7c>] __schedule+0x1ac/0xb10
[ 199.897841] [<ffffffff8131addd>] ? do_raw_spin_unlock+0x5d/0xb0
[ 199.897847] [<ffffffff810a6fdd>] ? trace_hardirqs_off+0xd/0x10
[ 199.897853] [<ffffffff815ca0c7>] ? _raw_spin_unlock_irqrestore+0x77/0x80
[ 199.897860] [<ffffffff8107f7ff>] ? try_to_wake_up+0x1ff/0x350
[ 199.897867] [<ffffffff810aac19>] ? __lock_acquire+0x3d9/0xb70
[ 199.897875] [<ffffffff8115c5b9>] ? kfree+0xa9/0x260
[ 199.897882] [<ffffffff810dc575>] ? __call_rcu+0x105/0x250
[ 199.897887] [<ffffffff8107c67a>] __cond_resched+0x2a/0x40
[ 199.897891] [<ffffffff815c855f>] _cond_resched+0x2f/0x40
[ 199.897898] [<ffffffff81182da8>] dput+0x128/0x1e0
[ 199.897902] [<ffffffff81169c78>] __fput+0x148/0x260
[ 199.897907] [<ffffffff8107981f>] ? finish_task_switch+0x3f/0x120
[ 199.897911] [<ffffffff81169e4e>] ____fput+0xe/0x10
[ 199.897917] [<ffffffff81067bbc>] task_work_run+0xbc/0xf0
[ 199.897923] [<ffffffff8105a4a9>] ptrace_notify+0x89/0x90
[ 199.897931] [<ffffffff8100fa1d>] syscall_trace_leave+0x8d/0x220
[ 199.897939] [<ffffffff815d39d1>] ? int_very_careful+0x5/0xd
[ 199.897944] [<ffffffff810ac555>] ? trace_hardirqs_on_caller+0x105/0x190
[ 199.897949] [<ffffffff815d3a0d>] int_check_syscall_exit_work+0x34/0x3d
-ss
prev parent reply other threads:[~2012-10-25 5:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-17 3:49 lots of suspicious RCU traces Dave Jones
2012-10-24 16:42 ` Sergey Senozhatsky
2012-10-24 18:06 ` Oleg Nesterov
2012-10-24 18:21 ` Sergey Senozhatsky
2012-10-24 18:52 ` Oleg Nesterov
2012-10-24 19:17 ` Sergey Senozhatsky
2012-10-24 19:41 ` Paul E. McKenney
2012-10-24 19:50 ` Sergey Senozhatsky
2012-10-24 20:11 ` Paul E. McKenney
2012-10-24 20:15 ` Sergey Senozhatsky
2012-10-24 22:32 ` Frederic Weisbecker
2012-10-25 5:50 ` Sergey Senozhatsky
2012-10-25 7:06 ` Frederic Weisbecker
2012-10-25 7:41 ` Sergey Senozhatsky
2012-10-26 9:40 ` [PATCH] rcu: Fix unrecovered RCU user mode in syscall_trace_leave() Frederic Weisbecker
2012-10-26 9:44 ` lots of suspicious RCU traces Frederic Weisbecker
2012-10-26 11:16 ` Sergey Senozhatsky
2012-10-26 15:16 ` Dave Jones
2012-10-25 5:55 ` Sergey Senozhatsky [this message]
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