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rcutorture: Update ->extendables check for lazy preemption

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The rcutorture_one_extend_check() function's second last check assumes
that "preempt_count() & PREEMPT_MASK" is non-zero only if
RCUTORTURE_RDR_PREEMPT or RCUTORTURE_RDR_SCHED bit is set.

This works for preemptible RCU and for non-preemptible RCU running in
a non-preemptible kernel.  But it fails for non-preemptible RCU running
in a preemptible kernel because then rcu_read_lock() is just
preempt_disable(), which increases preempt count.

This commit therefore adjusts this check to take into account the case
fo non-preemptible RCU running in a preemptible kernel.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Boqun Feng 2025-02-23 20:29:31 -08:00
parent 0be4b19edd
commit a56ca5619f
1 changed files with 10 additions and 2 deletions
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12
kernel/rcu/rcutorture.c
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@ -1901,8 +1901,16 @@ static void rcutorture_one_extend_check(char *s, int curstate, int new, int old,
WARN_ONCE(cur_ops->extendables &&
!(curstate & (RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH)) &&
(preempt_count() & SOFTIRQ_MASK), ROEC_ARGS);
WARN_ONCE(cur_ops->extendables &&
!(curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) &&
/*
* non-preemptible RCU in a preemptible kernel uses preempt_disable()
* as rcu_read_lock().
*/
mask = RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
if (!IS_ENABLED(CONFIG_PREEMPT_RCU))
mask |= RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;
WARN_ONCE(cur_ops->extendables && !(curstate & mask) &&
(preempt_count() & PREEMPT_MASK), ROEC_ARGS);
/*