Messages in this thread | | | Date | Wed, 28 Jun 2017 07:52:22 +0900 | From | Masami Hiramatsu <> | Subject | Re: [BUG] ftrace: WARNING: suspicious RCU usage |
| |
Hi,
On Tue, 27 Jun 2017 22:53:56 +0900 Masami Hiramatsu <mhiramat@kernel.org> wrote:
> > > [ 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.
Yes, the Commit 03ecd3f4 fixed only rcu_eqs_enter_common() path, but not rcu_eqs_exit().
> > > > > > Do you have this commit in this branch? > > > > Commit 03ecd3f4 "rcu/tracing: Add rcu_disabled to denote when > > rcu_irq_enter() will not work" > > Yes, that is merged. > > Hmm, I'll check this is correctly enabled again, since this time > I couldn't reproduce it.
I could reproduce it again with running full ftracetest (not sure why, but with only fgraph-filter-stack.tc, it is hard to be reproduced.
Please see attached patch, after applying that, I didn't see this problem.
Thank you,
-- Masami Hiramatsu <mhiramat@kernel.org> [unhandled content-type:application/octet-stream] | |