Re: [PATCH] Make rcutorture more vicious: reinstate boot-time testing

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

On Thu, Jun 19, 2008 at 02:17:25PM -0700, Randy Dunlap wrote:
> On Thu, 19 Jun 2008 08:58:54 -0700 Paul E. McKenney wrote:
> 
> > On Thu, Jun 19, 2008 at 11:29:14AM +0200, Ingo Molnar wrote:
> > > 
> > > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> > > 
> > > > Hello again!
> > > > 
> > 
> >  Documentation/RCU/torture.txt      |   21 
> >  Documentation/RCU/torture.txt.orig |    8 
>                                 ~~~~~
> 
> >  kernel/rcutorture.c                |   14 
> >  kernel/rcutorture.c.orig           |   59 
>                        !!!!
> 
> >  kernel/sysctl.c                    |   13 
> >  kernel/sysctl.c.orig               | 2851 +++++++++++++++++++++++++++++++++++++
>                    ~~~~
> 
> >  lib/Kconfig.debug                  |   20 
> >  lib/Kconfig.debug.orig             |  679 ++++++++
>                      ~~~~
> 
> What's with all of these .orig files, eh??

Gah, typos generating the diffs.  :-/

> >  8 files changed, 3651 insertions(+), 14 deletions(-)

How about the following instead?  (I expect to be following up with
a version that gets rid of the threads in response to writing a "0"
to /proc/sys/kernel/rcutorture_runnable later on.)

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

 Documentation/RCU/torture.txt |   21 ++++++++++++++-------
 kernel/rcutorture.c           |   14 ++++++++++++--
 kernel/sysctl.c               |   13 +++++++++++++
 lib/Kconfig.debug             |   20 +++++++++++++++++++-
 4 files changed, 58 insertions(+), 10 deletions(-)

diff -urpNa -X dontdiff linux-2.6.26-rc4-rcut1-stutter/Documentation/RCU/torture.txt linux-2.6.26-rc4-rcut2-proc/Documentation/RCU/torture.txt
--- linux-2.6.26-rc4-rcut1-stutter/Documentation/RCU/torture.txt	2008-06-18 05:15:43.000000000 -0700
+++ linux-2.6.26-rc4-rcut2-proc/Documentation/RCU/torture.txt	2008-06-18 08:11:19.000000000 -0700
@@ -10,13 +10,20 @@ status messages via printk(), which can 
 command (perhaps grepping for "torture").  The test is started
 when the module is loaded, and stops when the module is unloaded.
 
-However, actually setting this config option to "y" results in the system
-running the test immediately upon boot, and ending only when the system
-is taken down.  Normally, one will instead want to build the system
-with CONFIG_RCU_TORTURE_TEST=m and to use modprobe and rmmod to control
-the test, perhaps using a script similar to the one shown at the end of
-this document.  Note that you will need CONFIG_MODULE_UNLOAD in order
-to be able to end the test.
+CONFIG_RCU_TORTURE_TEST_RUNNABLE
+
+It is also possible to specify CONFIG_RCU_TORTURE_TEST=y, which will
+result in the tests being loaded into the base kernel.  In this case,
+the CONFIG_RCU_TORTURE_TEST_RUNNABLE config option is used to specify
+whether the RCU torture tests are to be started immediately during
+boot or whether the /proc/sys/kernel/rcutorture_runnable file is used
+to enable them.  This /proc file can be used to repeatedly pause and
+restart the tests, regardless of the initial state specified by the
+CONFIG_RCU_TORTURE_TEST_RUNNABLE config option.
+
+You will normally -not- want to start the RCU torture tests during boot
+(and thus the default is CONFIG_RCU_TORTURE_TEST_RUNNABLE=n), but doing
+this can sometimes be useful in finding boot-time bugs.
 
 
 MODULE PARAMETERS
diff -urpNa -X dontdiff linux-2.6.26-rc4-rcut1-stutter/kernel/rcutorture.c linux-2.6.26-rc4-rcut2-proc/kernel/rcutorture.c
--- linux-2.6.26-rc4-rcut1-stutter/kernel/rcutorture.c	2008-06-18 04:54:41.000000000 -0700
+++ linux-2.6.26-rc4-rcut2-proc/kernel/rcutorture.c	2008-06-19 04:48:56.000000000 -0700
@@ -125,6 +125,13 @@ static struct list_head rcu_torture_remo
 
 static int stutter_pause_test = 0;
 
+#if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
+#define RCUTORTURE_RUNNABLE_INIT 1
+#else
+#define RCUTORTURE_RUNNABLE_INIT 0
+#endif
+int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT;
+
 /*
  * Allocate an element from the rcu_tortures pool.
  */
@@ -188,8 +195,11 @@ rcu_random(struct rcu_random_state *rrsp
 static void
 rcu_stutter_wait(void)
 {
-	while (stutter_pause_test)
-		schedule_timeout_interruptible(1);
+	while (stutter_pause_test || !rcutorture_runnable)
+		if (rcutorture_runnable)
+			schedule_timeout_interruptible(1);
+		else
+			schedule_timeout_interruptible(HZ);
 }
 
 /*
diff -urpNa -X dontdiff linux-2.6.26-rc4-rcut1-stutter/kernel/sysctl.c linux-2.6.26-rc4-rcut2-proc/kernel/sysctl.c
--- linux-2.6.26-rc4-rcut1-stutter/kernel/sysctl.c	2008-05-30 04:39:01.000000000 -0700
+++ linux-2.6.26-rc4-rcut2-proc/kernel/sysctl.c	2008-06-18 07:35:26.000000000 -0700
@@ -82,6 +82,9 @@ extern int maps_protect;
 extern int sysctl_stat_interval;
 extern int latencytop_enabled;
 extern int sysctl_nr_open_min, sysctl_nr_open_max;
+#ifdef CONFIG_RCU_TORTURE_TEST
+extern int rcutorture_runnable;
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
 
 /* Constants used for minimum and  maximum */
 #if defined(CONFIG_DETECT_SOFTLOCKUP) || defined(CONFIG_HIGHMEM)
@@ -813,6 +816,16 @@ static struct ctl_table kern_table[] = {
 		.child		= key_sysctls,
 	},
 #endif
+#ifdef CONFIG_RCU_TORTURE_TEST
+	{
+		.ctl_name       = CTL_UNNUMBERED,
+		.procname       = "rcutorture_runnable",
+		.data           = &rcutorture_runnable,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = &proc_dointvec,
+	},
+#endif
 /*
  * NOTE: do not add new entries to this table unless you have read
  * Documentation/sysctl/ctl_unnumbered.txt
diff -urpNa -X dontdiff linux-2.6.26-rc4-rcut1-stutter/lib/Kconfig.debug linux-2.6.26-rc4-rcut2-proc/lib/Kconfig.debug
--- linux-2.6.26-rc4-rcut1-stutter/lib/Kconfig.debug	2008-05-30 04:39:01.000000000 -0700
+++ linux-2.6.26-rc4-rcut2-proc/lib/Kconfig.debug	2008-06-18 06:32:48.000000000 -0700
@@ -531,16 +531,34 @@ config BOOT_PRINTK_DELAY
 config RCU_TORTURE_TEST
 	tristate "torture tests for RCU"
 	depends on DEBUG_KERNEL
-	depends on m
 	default n
 	help
 	  This option provides a kernel module that runs torture tests
 	  on the RCU infrastructure.  The kernel module may be built
 	  after the fact on the running kernel to be tested, if desired.
 
+	  Say Y here if you want RCU torture tests to be built into
+	  the kernel.
 	  Say M if you want the RCU torture tests to build as a module.
 	  Say N if you are unsure.
 
+config RCU_TORTURE_TEST_RUNNABLE
+	bool "torture tests for RCU runnable by default"
+	depends on RCU_TORTURE_TEST = y
+	default n
+	help
+	  This option provides a way to build the RCU torture tests
+	  directly into the kernel without them starting up at boot
+	  time.  You can use /proc/sys/kernel/rcutorture_runnable
+	  to manually override this setting.  This /proc file is
+	  available only when the RCU torture tests have been built
+	  into the kernel.
+
+	  Say Y here if you want the RCU torture tests to start during
+	  boot (you probably don't).
+	  Say N here if you want the RCU torture tests to start only
+	  after being manually enabled via /proc.
+
 config KPROBES_SANITY_TEST
 	bool "Kprobes sanity tests"
 	depends on DEBUG_KERNEL