From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753268AbcDXVbR (ORCPT ); Sun, 24 Apr 2016 17:31:17 -0400 Received: from e18.ny.us.ibm.com ([129.33.205.208]:49475 "EHLO e18.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753124AbcDXVbQ (ORCPT ); Sun, 24 Apr 2016 17:31:16 -0400 X-IBM-Helo: d01dlp03.pok.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Sun, 24 Apr 2016 14:31:47 -0700 From: "Paul E. McKenney" To: Guenter Roeck Cc: Boqun Feng , Josh Triplett , Steven Rostedt , linux-kernel@vger.kernel.org Subject: Re: next: suspicious RCU usage message since commit 'rcu: Remove superfluous versions of rcu_read_lock_sched_held()' Message-ID: <20160424213147.GW3756@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20160424211424.GA20388@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160424211424.GA20388@roeck-us.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16042421-0045-0000-0000-000003FE82FD Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 24, 2016 at 02:14:24PM -0700, Guenter Roeck wrote: > Hi, > > I see the following log message when running a qemu test for 'beagle' > with omap2plus_defconfig. > > =============================== > [ INFO: suspicious RCU usage. ] > 4.6.0-rc4-next-20160422 #1 Not tainted > ------------------------------- > include/trace/events/power.h:328 suspicious rcu_dereference_check() usage! > > 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! > no locks held by swapper/0/0. > > stack backtrace: > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc4-next-20160422 #1 > Hardware name: Generic OMAP3-GP (Flattened Device Tree) > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > [] (show_stack) from [] (dump_stack+0xa8/0xe0) > [] (dump_stack) from [] (pwrdm_set_next_pwrst+0xf8/0x1cc) > [] (pwrdm_set_next_pwrst) from [] (omap3_enter_idle_bm+0x1b8/0x1e8) > [] (omap3_enter_idle_bm) from [] (cpuidle_enter_state+0x84/0x408) > [] (cpuidle_enter_state) from [] (cpu_startup_entry+0x1c8/0x3f0) > [] (cpu_startup_entry) from [] (start_kernel+0x354/0x3cc) > > bisect points to commit 'rcu: Remove superfluous versions of > rcu_read_lock_sched_held()'. Bisect log is attached. I believe that the real fix is not a revert of that commit, but rather that some of the tracing statements need an "_rcuidle" suffix. Something like the following (untested, probably does not build) patch. Thanx, Paul ------------------------------------------------------------------------ commit ca91304178e1cf53ee391236a0ac3969cc814e5f Author: Paul E. McKenney Date: Sun Apr 24 14:30:16 2016 -0700 arm: Use _rcuidle tracepoint to allow use from idle Signed-off-by: Paul E. McKenney diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c index 78af6d8cf2e2..12b66b5bcc55 100644 --- a/arch/arm/mach-omap2/powerdomain.c +++ b/arch/arm/mach-omap2/powerdomain.c @@ -523,8 +523,8 @@ int pwrdm_set_next_pwrst(struct powerdomain *pwrdm, u8 pwrst) if (arch_pwrdm && arch_pwrdm->pwrdm_set_next_pwrst) { /* Trace the pwrdm desired target state */ - trace_power_domain_target(pwrdm->name, pwrst, - smp_processor_id()); + trace_power_domain_target_rcuidle(pwrdm->name, pwrst, + smp_processor_id()); /* Program the pwrdm desired target state */ ret = arch_pwrdm->pwrdm_set_next_pwrst(pwrdm, pwrst); }