rcutorture's tasks flavor models a Tasks RCU reader as "any stretch of kernel code", and rcu_read_delay() deliberately preempts inside it to check that a preemption does not end the read-side critical section. Once preemption outside a trampoline becomes a quiescent state that model no longer matches what Tasks RCU protects, and the readers would report false too-short grace periods. Have tasks_torture_read_lock()/unlock() raise and drop current->rcu_tramp_nesting so the reader models a trampoline, which is the thing Tasks RCU actually guards; the deliberate preemption inside it then continues to be, correctly, not a quiescent state. Assisted-by: LLM Signed-off-by: Josef Bacik --- kernel/rcu/rcutorture.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 794937e13e7c..df6dd708cea7 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1144,11 +1144,17 @@ static struct rcu_torture_ops trivial_preempt_ops = { static int tasks_torture_read_lock(void) { + /* + * Model a trampoline: with CONFIG_RCU_TASKS_PREEMPT_QS a preemption is + * otherwise a quiescent state and rcu_read_delay() preempts on purpose. + */ + rcu_tasks_trampoline_enter(); return 0; } static void tasks_torture_read_unlock(int idx) { + rcu_tasks_trampoline_exit(); } static void rcu_tasks_torture_deferred_free(struct rcu_torture *p) -- 2.55.0