Commit 620316e5 authored Jan 30, 2016 by Paul E. McKenney

rcutorture: Avoid RCU CPU stall warning and RT throttling

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 <paulmck@linux.vnet.ibm.com>

parent df37e66b

kernel/rcu/rcuperf.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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;