rcuperf: Don't treat gp_exp mis-setting as a WARN (af06d4f7) · Commits · 戴 / test

0day found a boot warning triggered in rcu_perf_writer() on !SMP kernel: WARN_ON(rcu_gp_is_normal() && gp_exp); , the root cause of which is trying to measure expedited grace periods(by setting gp_exp to true by default) when all the grace periods are normal(TINY RCU only has normal grace periods). However, such a mis-setting would only result in failing to measure the performance for a specific kind of grace periods, therefore using a WARN_ON to check this is a little overkilling. We could handle this inside rcuperf module via some error messages to tell users about the mis-settings. Therefore this patch removes the WARN_ON in rcu_perf_writer() and handles those checkings in rcu_perf_init() with plain if() code. Moreover, this patch changes the default value of gp_exp to 1) align with rcutorture tests and 2) make the default setting work for all RCU implementations by default. Suggested-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by:

Boqun Feng <boqun.feng@gmail.com> Fixes: http://lkml.kernel.org/r/57411b10.mFvG0+AgcrMXGtcj%fengguang.wu@intel.com Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/rcuperf.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -58,7 +58,7 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>");
		#define VERBOSE_PERFOUT_ERRSTRING(s) \
		do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)

		torture_param(bool, gp_exp, true, "Use expedited GP wait primitives");
		torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
		torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
		torture_param(int, nreaders, -1, "Number of RCU reader threads");
		torture_param(int, nwriters, -1, "Number of RCU updater threads");
		@@ -358,8 +358,6 @@ rcu_perf_writer(void *arg)
		u64 *wdpp = writer_durations[me];

		VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
		WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp);
		WARN_ON(rcu_gp_is_normal() && gp_exp);
		WARN_ON(!wdpp);
		set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
		sp.sched_priority = 1;
		@@ -626,6 +624,16 @@ rcu_perf_init(void)
		firsterr = -ENOMEM;
		goto unwind;
		}
		if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp) {
		VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
		firsterr = -EINVAL;
		goto unwind;
		}
		if (rcu_gp_is_normal() && gp_exp) {
		VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
		firsterr = -EINVAL;
		goto unwind;
		}
		for (i = 0; i < nrealwriters; i++) {
		writer_durations[i] =
		kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),

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