Messages in this thread | | | Date | Tue, 27 Jun 2017 09:29:26 -0400 | From | Steven Rostedt <> | Subject | Re: [BUG] ftrace: WARNING: suspicious RCU usage |
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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, >
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