From 31a72bce0bd6f3e0114009288bccbc96376eeeca Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 18 Jun 2008 09:26:49 -0700 Subject: rcu: make rcutorture more vicious: reinstate boot-time testing This patch re-institutes the ability to build rcutorture directly into the Linux kernel. The reason that this capability was removed was that this could result in your kernel being pretty much useless, as rcutorture would be running starting from early boot. This problem has been avoided by (1) making rcutorture run only three seconds of every six by default, (2) adding a CONFIG_RCU_TORTURE_TEST_RUNNABLE that permits rcutorture to be quiesced at boot time, and (3) adding a sysctl in /proc named /proc/sys/kernel/rcutorture_runnable that permits rcutorture to be quiesced and unquiesced when built into the kernel. Please note that this /proc file is -not- available when rcutorture is built as a module. Please also note that to get the earlier take-no-prisoners behavior, you must use the boot command line to set rcutorture's "stutter" parameter to zero. The rcutorture quiescing mechanism is currently quite crude: loops in each rcutorture process that poll a global variable once per tick. Suggestions for improvement are welcome. The default action will be to reduce the polling rate to a few times per second. Signed-off-by: Paul E. McKenney Suggested-by: Ingo Molnar Signed-off-by: Ingo Molnar --- kernel/rcutorture.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'kernel/rcutorture.c') diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 98ae7d168225..27003e2421c7 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -125,6 +125,13 @@ static struct list_head rcu_torture_removed; 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. */ @@ -188,7 +195,7 @@ rcu_random(struct rcu_random_state *rrsp) static void rcu_stutter_wait(void) { - while (stutter_pause_test) + while (stutter_pause_test || !rcutorture_runnable) schedule_timeout_interruptible(1); } -- cgit v1.2.2