linux-kernel - [BUG] ftrace: WARNING: suspicious RCU usage

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Date:   Tue, 27 Jun 2017 20:51:26 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [BUG] ftrace: WARNING: suspicious RCU usage

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
[   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
[   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,

-- 
Masami Hiramatsu <mhiramat@...nel.org>

View attachment "ftrace-core-rcubug.log" of type "text/plain" (12909 bytes)

Download attachment "ftrace-core-rcubug.kconfig" of type "application/octet-stream" (73405 bytes)