From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [BUG] ftrace: WARNING: suspicious RCU usage
Date: Tue, 27 Jun 2017 09:29:26 -0400 [thread overview]
Message-ID: <20170627092926.0d712e3a@gandalf.local.home> (raw)
In-Reply-To: <20170627205126.6c5261d10472539b528ca144@kernel.org>
On Tue, 27 Jun 2017 20:51:26 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> Hello Steve,
>
> I've faced the following RCU warning while I ran ftracetest testcase
> "ftrace - function graph filters with stack tracer" on qemu.
> The kernel is ftrace/core branch.
>
> [ 10.919174] =============================
> [ 10.920077] WARNING: suspicious RCU usage
> [ 10.920977] 4.12.0-rc5+ #1 Not tainted
> [ 10.921828] -----------------------------
> [ 10.922748] /home/mhiramat/ksrc/linux/include/trace/events/rcu.h:454 suspicious rcu_dereference_check() usage!
> [ 10.924761]
> [ 10.924761] other info that might help us debug this:
> [ 10.924761]
> [ 10.926775]
> [ 10.926775] RCU used illegally from idle CPU!
> [ 10.926775] rcu_scheduler_active = 2, debug_locks = 1
> [ 10.929176] RCU used illegally from extended quiescent state!
> [ 10.930525] no locks held by swapper/7/0.
> [ 10.931547]
> [ 10.931547] stack backtrace:
> [ 10.932777] CPU: 7 PID: 0 Comm: swapper/7 Not tainted 4.12.0-rc5+ #1
> [ 10.934025] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-1.fc25 04/01/2014
> [ 10.935869] Call Trace:
> [ 10.936550] dump_stack+0x86/0xcf
> [ 10.937359] lockdep_rcu_suspicious+0xc5/0x100
> [ 10.938327] ? rcu_eqs_exit_common.isra.53+0x5/0x150
> [ 10.939229] rcu_irq_enter+0x18d/0x1a0
Strange, it triggered in rcu_irq_enter()?
> [ 10.939902] ? rcu_eqs_exit_common.isra.53+0x5/0x150
> [ 10.940683] check_stack+0xbb/0x2f0
> [ 10.941333] stack_trace_call+0x3f/0x50
> [ 10.942010] 0xffffffffa0000077
> [ 10.942620] ? ftrace_graph_caller+0x78/0xa8
> [ 10.943342] ? rcu_eqs_exit_common.isra.53+0x5/0x150
> [ 10.944214] ? rcu_idle_exit+0x5/0x90
> [ 10.944937] rcu_eqs_exit_common.isra.53+0x5/0x150
Hmm, we are tracing rcu_eqs_exit_common.
Do you have this commit in this branch?
Commit 03ecd3f4 "rcu/tracing: Add rcu_disabled to denote when
rcu_irq_enter() will not work"
-- Steve
> [ 10.945754] rcu_idle_exit+0x8c/0x90
> [ 10.946612] ? rcu_eqs_exit_common.isra.53+0x5/0x150
> [ 10.947414] ? rcu_idle_exit+0x8c/0x90
> [ 10.948091] do_idle+0x116/0x1c0
> [ 10.948797] cpu_startup_entry+0x1d/0x20
> [ 10.949569] start_secondary+0xfa/0x100
> [ 10.950335] secondary_startup_64+0x9f/0x9f
> [ 10.951182]
>
> I attached full log and kconfig. I can reproduce it with just running
> following script.
>
> ----
> cd tools/testing/selftests/ftrace
> while true; do
> ./ftracetest test.d/ftrace/fgraph-filter-stack.tc
> done
> ----
>
> Thank you,
>
next prev parent reply other threads:[~2017-06-27 13:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-27 11:51 [BUG] ftrace: WARNING: suspicious RCU usage Masami Hiramatsu
2017-06-27 13:29 ` Steven Rostedt [this message]
2017-06-27 13:53 ` Masami Hiramatsu
2017-06-27 22:52 ` Masami Hiramatsu
2017-06-27 22:57 ` Steven Rostedt
2017-06-28 0:44 ` Paul E. McKenney
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