On Wed, May 22, 2013 at 08:49:18AM -0400, Steven Rostedt wrote:
> > ===============================
> > [ INFO: suspicious RCU usage. ]
> > 3.10.0-rc2+ #1 Not tainted
> > -------------------------------
> > include/linux/rcupdate.h:771 rcu_read_lock() used illegally while idle!
> > other info that might help us debug this:
> > RCU used illegally from idle CPU! rcu_scheduler_active = 1, debug_locks = 0
> > RCU used illegally from extended quiescent state!
> > 2 locks held by cc1/63645:
> > #0: (&rq->lock){-.-.-.}, at: [<ffffffff816b39fd>] __schedule+0xed/0x9b0
> > #1: (rcu_read_lock){.+.+..}, at: [<ffffffff8109d645>]
> > cpuacct_charge+0x5/0x1f0
> >
> > CPU: 1 PID: 63645 Comm: cc1 Not tainted 3.10.0-rc2+ #1 [loadavg: 40.57
> > 27.55 13.39 25/277 64369]
> > Hardware name: Gigabyte Technology Co., Ltd. GA-MA78GM-S2H/GA-MA78GM-S2H,
> > BIOS F12a 04/23/2010
> > 0000000000000000 ffff88010f78fcf8 ffffffff816ae383 ffff88010f78fd28
> > ffffffff810b698d ffff88011c092548 000000000023d073 ffff88011c092500
> > 0000000000000001 ffff88010f78fd60 ffffffff8109d7c5 ffffffff8109d645
> > Call Trace:
> > [<ffffffff816ae383>] dump_stack+0x19/0x1b
> > [<ffffffff810b698d>] lockdep_rcu_suspicious+0xfd/0x130
> > [<ffffffff8109d7c5>] cpuacct_charge+0x185/0x1f0
> > [<ffffffff8109d645>] ? cpuacct_charge+0x5/0x1f0
> > [<ffffffff8108dffc>] update_curr+0xec/0x240
> > [<ffffffff8108f528>] put_prev_task_fair+0x228/0x480
> > [<ffffffff816b3a71>] __schedule+0x161/0x9b0
> > [<ffffffff816b4721>] preempt_schedule+0x51/0x80
> > [<ffffffff816b4800>] ? __cond_resched_softirq+0x60/0x60
> > [<ffffffff816b6824>] ? retint_careful+0x12/0x2e
> > [<ffffffff810ff3cc>] ftrace_ops_control_func+0x1dc/0x210
> > [<ffffffff816be280>] ftrace_call+0x5/0x2f
> > [<ffffffff816b681d>] ? retint_careful+0xb/0x2e
> > [<ffffffff816b4805>] ? schedule_user+0x5/0x70
> > [<ffffffff816b4805>] ? schedule_user+0x5/0x70
> > [<ffffffff816b6824>] ? retint_careful+0x12/0x2e
> > ------------[ cut here ]------------
>
> This looks to be the caused by the same issue that this patch fixes:
>
> https://lkml.org/lkml/2013/5/10/537
>
> The schedule_user() was traced, and the preempt_enable_no_trace() that
> the function tracer does caused for a schedule to occur. As the
> scheduler uses rcu, and it was called before schedule_user() could tell
> the kernel that the context is changing from user to kernel.
That patch doesn't help unfortunatly.
Dave
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