[PATCH rcu 12/18] rcutorture: Ignore attempts to test preemption and forward progress

[Paul E. McKenney]

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 <paul...@kernel.org>
---
 kernel/rcu/rcutorture.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 8c7820a00f3c3..3595ce889b44f 100644
--- 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)
-- 
2.40.1