rcutorture: Ignore attempts to test preemption and forward progress

Use of the rcutorture preempt_duration and the default-on fwd_progress
kernel parameters can result in preemption of callback processing during
forward-progress testing, which is an excellent way to OOM your test
if your kernel offloads RCU callbacks.  This commit therefore treats
preempt_duration in the same way as stall_cpu in CONFIG_RCU_NOCB_CPU=y
kernels, prohibiting fwd_progress testing and splatting when rcutorture
is built in (as opposed to being a loadable module).

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 8c7820a00f3c35b2b67de964e6d45826ed76b80d..3595ce889b44fb315c8de15f2dd04ca567679dc4 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -3145,12 +3145,12 @@ static int __init rcu_torture_fwd_prog_init(void)
                fwd_progress = 0;
                return 0;
        }
-       if (stall_cpu > 0) {
-               VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
+       if (stall_cpu > 0 || (preempt_duration > 0 && IS_ENABLED(CONFIG_RCU_NOCB_CPU))) {
+               VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall and/or preemption testing");
                fwd_progress = 0;
                if (IS_MODULE(CONFIG_RCU_TORTURE_TEST))
                        return -EINVAL; /* In module, can fail back to user. */
-               WARN_ON(1); /* Make sure rcutorture notices conflict. */
+               WARN_ON(1); /* Make sure rcutorture scripting notices conflict. */
                return 0;
        }
        if (fwd_progress_holdoff <= 0)