rcutorture: Vary forward-progress test interval

Some of the Linux kernel's RCU implementations provide several mechanisms
to promote forward progress that operate over different timeframes.
This commit therefore causes rcu_torture_fwd_prog() to vary the duration
of its forward-progress testing in order to test each such mechanism.

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

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 8ab23143c24447911dd75c25961ed67cbfbef086..89cc4d9c9a0cdc1eaed1d2b6700b32d7876ebf5b 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1676,16 +1676,21 @@ static int rcu_torture_fwd_prog(void *args)
        unsigned long cver;
        unsigned long gps;
        int idx;
+       int sd;
+       int sd4;
        unsigned long stopat;
        bool tested = false;
        int tested_tries = 0;
+       static DEFINE_TORTURE_RANDOM(trs);
 
        VERBOSE_TOROUT_STRING("rcu_torture_fwd_progress task started");
        do {
                schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
                cver = READ_ONCE(rcu_torture_current_version);
                gps = cur_ops->get_gp_seq();
-               stopat = jiffies + cur_ops->stall_dur() / fwd_progress_div;
+               sd = cur_ops->stall_dur() + 1;
+               sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
+               stopat = jiffies + sd4 + torture_random(&trs) % (sd - sd4);
                while (time_before(jiffies, stopat) && !torture_must_stop()) {
                        idx = cur_ops->readlock();
                        udelay(10);