locktorture: Make the rt_boost factor a tunable

The rt boosting in locktorture has a factor variable s currently large enough
that boosting only happens once every minute or so. Add a tunable to reduce the
factor so that boosting happens more often, to test paths and arrive at failure
modes earlier. With this change, I can set the factor to like 50 and have the
boosting happens every 10 seconds or so.

Tested with boot parameters:
locktorture.torture_type=mutex_lock
locktorture.onoff_interval=1
locktorture.nwriters_stress=8
locktorture.stutter=0
locktorture.rt_boost=1
locktorture.rt_boost_factor=50
locktorture.nlocks=3

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index e2271e8fc302763f2f1b8e60722b58d193c1af57..f04b1978899dda4185697b6d2d69bbdf02c1ea38 100644 (file)
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -48,6 +48,7 @@ torture_param(int, stat_interval, 60,
 torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
 torture_param(int, rt_boost, 2,
                "Do periodic rt-boost. 0=Disable, 1=Only for rt_mutex, 2=For all lock types.");
+torture_param(int, rt_boost_factor, 50, "A factor determining how often rt-boost happens.");
 torture_param(int, verbose, 1,
             "Enable verbose debugging printk()s");
 
@@ -131,12 +132,12 @@ static void torture_lock_busted_write_unlock(int tid __maybe_unused)
 
 static void __torture_rt_boost(struct torture_random_state *trsp)
 {
-       const unsigned int factor = 50000; /* yes, quite arbitrary */
+       const unsigned int factor = rt_boost_factor;
 
        if (!rt_task(current)) {
                /*
-                * Boost priority once every ~50k operations. When the
-                * task tries to take the lock, the rtmutex it will account
+                * Boost priority once every rt_boost_factor operations. When
+                * the task tries to take the lock, the rtmutex it will account
                 * for the new priority, and do any corresponding pi-dance.
                 */
                if (trsp && !(torture_random(trsp) %
@@ -146,8 +147,9 @@ static void __torture_rt_boost(struct torture_random_state *trsp)
                        return;
        } else {
                /*
-                * The task will remain boosted for another ~500k operations,
-                * then restored back to its original prio, and so forth.
+                * The task will remain boosted for another 10 * rt_boost_factor
+                * operations, then restored back to its original prio, and so
+                * forth.
                 *
                 * When @trsp is nil, we want to force-reset the task for
                 * stopping the kthread.