From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030274AbcDLPth (ORCPT ); Tue, 12 Apr 2016 11:49:37 -0400 Received: from e18.ny.us.ibm.com ([129.33.205.208]:59757 "EHLO e18.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965748AbcDLPnn (ORCPT ); Tue, 12 Apr 2016 11:43:43 -0400 X-IBM-Helo: d01dlp02.pok.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 12/24] rcutorture: Avoid RCU CPU stall warning and RT throttling Date: Tue, 12 Apr 2016 08:43:45 -0700 Message-Id: <1460475837-26498-12-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <20160412154332.GA24983@linux.vnet.ibm.com> References: <20160412154332.GA24983@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16041215-0045-0000-0000-000003E4640B Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Running rcuperf can result in RCU CPU stall warnings and RT throttling. These occur because on of the real-time writer processes does ftrace_dump() while still running at real-time priority. This commit therefore prevents these problems by setting the writer thread back to SCHED_NORMAL (AKA SCHED_OTHER) before doing ftrace_dump(). In addition, this commit adds a small fixed delay before dumping ftrace buffer in order to decrease the probability that this dumping will interfere with other writers' grace periods. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcuperf.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index 278600143bb6..4c0572859ff0 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -404,11 +404,15 @@ rcu_perf_writer(void *arg) started = true; if (!done && i >= MIN_MEAS) { done = true; + sp.sched_priority = 0; + sched_setscheduler_nocheck(current, + SCHED_NORMAL, &sp); pr_alert("%s" PERF_FLAG "rcu_perf_writer %ld has %d measurements\n", perf_type, me, MIN_MEAS); if (atomic_inc_return(&n_rcu_perf_writer_finished) >= nrealwriters) { + schedule_timeout_interruptible(10); rcu_ftrace_dump(DUMP_ALL); PERFOUT_STRING("Test complete"); t_rcu_perf_writer_finished = t; -- 2.5.2