diff mbox

[RFC,tip/core/rcu,30/41] rcutorture: Permit holding off CPU-hotplug operations during boot

Message ID 1328125319-5205-30-git-send-email-paulmck@linux.vnet.ibm.com
State New
Headers show

Commit Message

Paul E. McKenney Feb. 1, 2012, 7:41 p.m. UTC 
From: "Paul E. McKenney" <paul.mckenney@linaro.org>

When rcutorture is started automatically at boot time, it might well
also start CPU-hotplug operations at that time, which might not be
desirable.  This commit therefore adds an rcutorture parameter that
allows CPU-hotplug operations to be held off for the specified number
of seconds after the start of boot.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 Documentation/RCU/torture.txt |   15 ++++++++++++---
 kernel/rcutorture.c           |   12 ++++++++++--
 2 files changed, 22 insertions(+), 5 deletions(-)

Comments

Josh Triplett Feb. 2, 2012, 5:43 a.m. UTC | #1 
On Wed, Feb 01, 2012 at 11:41:48AM -0800, Paul E. McKenney wrote:
> When rcutorture is started automatically at boot time, it might well
> also start CPU-hotplug operations at that time, which might not be
> desirable.  This commit therefore adds an rcutorture parameter that
> allows CPU-hotplug operations to be held off for the specified number
> of seconds after the start of boot.
> --- a/Documentation/RCU/torture.txt
> +++ b/Documentation/RCU/torture.txt
> @@ -271,11 +278,13 @@ The following script may be used to torture RCU:
>  	#!/bin/sh
>  
>  	modprobe rcutorture
> -	sleep 100
> +	sleep 3600
>  	rmmod rcutorture
>  	dmesg | grep torture:

This looks like an entirely unrelated change.

- Josh Triplett
Paul E. McKenney Feb. 2, 2012, 5:56 p.m. UTC | #2 
On Wed, Feb 01, 2012 at 09:43:00PM -0800, Josh Triplett wrote:
> On Wed, Feb 01, 2012 at 11:41:48AM -0800, Paul E. McKenney wrote:
> > When rcutorture is started automatically at boot time, it might well
> > also start CPU-hotplug operations at that time, which might not be
> > desirable.  This commit therefore adds an rcutorture parameter that
> > allows CPU-hotplug operations to be held off for the specified number
> > of seconds after the start of boot.
> > --- a/Documentation/RCU/torture.txt
> > +++ b/Documentation/RCU/torture.txt
> > @@ -271,11 +278,13 @@ The following script may be used to torture RCU:
> >  	#!/bin/sh
> >  
> >  	modprobe rcutorture
> > -	sleep 100
> > +	sleep 3600
> >  	rmmod rcutorture
> >  	dmesg | grep torture:
> 
> This looks like an entirely unrelated change.

I suppose it is.  I did split it out, though a one-line documentation change
seems a bit lightweight for a commit.

								Thanx, Paul
diff mbox

Patch

diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index d67068d..d25be87 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -69,6 +69,13 @@  onoff_interval
 		CPU-hotplug operations regardless of what value is
 		specified for onoff_interval.
 
+onoff_holdoff	The number of seconds to wait until starting CPU-hotplug
+		operations.  This would normally only be used when
+		rcutorture was built into the kernel and started
+		automatically at boot time, in which case it is useful
+		in order to avoid confusing boot-time code with CPUs
+		coming and going.
+
 shuffle_interval
 		The number of seconds to keep the test threads affinitied
 		to a particular subset of the CPUs, defaults to 3 seconds.
@@ -271,11 +278,13 @@  The following script may be used to torture RCU:
 	#!/bin/sh
 
 	modprobe rcutorture
-	sleep 100
+	sleep 3600
 	rmmod rcutorture
 	dmesg | grep torture:
 
 The output can be manually inspected for the error flag of "!!!".
 One could of course create a more elaborate script that automatically
-checked for such errors.  The "rmmod" command forces a "SUCCESS" or
-"FAILURE" indication to be printk()ed.
+checked for such errors.  The "rmmod" command forces a "SUCCESS",
+"FAILURE", or "RCU_HOTPLUG" indication to be printk()ed.  The first
+two are self-explanatory, while the last indicates that while there
+were no RCU failures, CPU-hotplug problems were detected.
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index a94eaef..eeafbd0 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -65,6 +65,7 @@  static int fqs_duration;	/* Duration of bursts (us), 0 to disable. */
 static int fqs_holdoff;		/* Hold time within burst (us). */
 static int fqs_stutter = 3;	/* Wait time between bursts (s). */
 static int onoff_interval;	/* Wait time between CPU hotplugs, 0=disable. */
+static int onoff_holdoff;	/* Seconds after boot before CPU hotplugs. */
 static int shutdown_secs;	/* Shutdown time (s).  <=0 for no shutdown. */
 static int test_boost = 1;	/* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */
 static int test_boost_interval = 7; /* Interval between boost tests, seconds. */
@@ -95,6 +96,8 @@  module_param(fqs_stutter, int, 0444);
 MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
 module_param(onoff_interval, int, 0444);
 MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
+module_param(onoff_holdoff, int, 0444);
+MODULE_PARM_DESC(onoff_holdoff, "Time after boot before CPU hotplugs (s)");
 module_param(shutdown_secs, int, 0444);
 MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), zero to disable.");
 module_param(test_boost, int, 0444);
@@ -1300,13 +1303,13 @@  rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
 		"fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
 		"test_boost=%d/%d test_boost_interval=%d "
 		"test_boost_duration=%d shutdown_secs=%d "
-		"onoff_interval=%d\n",
+		"onoff_interval=%d onoff_holdoff=%d\n",
 		torture_type, tag, nrealreaders, nfakewriters,
 		stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
 		test_boost, cur_ops->can_boost,
 		test_boost_interval, test_boost_duration, shutdown_secs,
-		onoff_interval);
+		onoff_interval, onoff_holdoff);
 }
 
 static struct notifier_block rcutorture_shutdown_nb = {
@@ -1410,6 +1413,11 @@  rcu_torture_onoff(void *arg)
 	for_each_online_cpu(cpu)
 		maxcpu = cpu;
 	WARN_ON(maxcpu < 0);
+	if (onoff_holdoff > 0) {
+		VERBOSE_PRINTK_STRING("rcu_torture_onoff begin holdoff");
+		schedule_timeout_interruptible(onoff_holdoff * HZ);
+		VERBOSE_PRINTK_STRING("rcu_torture_onoff end holdoff");
+	}
 	while (!kthread_should_stop()) {
 		cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
 		if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {