From 512bf713cb4c8a42ae76e5ba1a78e70a768af301 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Mon, 29 Nov 2021 18:46:50 +0100 Subject: lockdep/selftests: Unbalanced migrate_disable() & rcu_read_lock(). The tests with unbalanced lock() + unlock() operation leave a modified preemption counter behind which is then reset to its original value after the test. The spin_lock() function on PREEMPT_RT does not include a preempt_disable() statement but migrate_disable() and read_rcu_lock(). As a consequence both counter never get back to their original value and the system explodes later after the selftest. In the double-unlock case on PREEMPT_RT, the migrate_disable() and RCU code will trigger a warning which should be avoided. These counter should not be decremented below their initial value. Save both counters and bring them back to their original value after the test. In the double-unlock case, increment both counter in advance to they become balanced after the double unlock. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20211129174654.668506-8-bigeasy@linutronix.de --- lib/locking-selftest.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) (limited to 'lib/locking-selftest.c') diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 4d614c74e6ec..417056ba28e1 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -712,12 +712,18 @@ GENERATE_TESTCASE(ABCDBCDA_rtmutex); #undef E +#ifdef CONFIG_PREEMPT_RT +# define RT_PREPARE_DBL_UNLOCK() { migrate_disable(); rcu_read_lock(); } +#else +# define RT_PREPARE_DBL_UNLOCK() +#endif /* * Double unlock: */ #define E() \ \ LOCK(A); \ + RT_PREPARE_DBL_UNLOCK(); \ UNLOCK(A); \ UNLOCK(A); /* fail */ @@ -1398,7 +1404,13 @@ static int unexpected_testcase_failures; static void dotest(void (*testcase_fn)(void), int expected, int lockclass_mask) { - unsigned long saved_preempt_count = preempt_count(); + int saved_preempt_count = preempt_count(); +#ifdef CONFIG_PREEMPT_RT +#ifdef CONFIG_SMP + int saved_mgd_count = current->migration_disabled; +#endif + int saved_rcu_count = current->rcu_read_lock_nesting; +#endif WARN_ON(irqs_disabled()); @@ -1432,6 +1444,18 @@ static void dotest(void (*testcase_fn)(void), int expected, int lockclass_mask) * count, so restore it: */ preempt_count_set(saved_preempt_count); + +#ifdef CONFIG_PREEMPT_RT +#ifdef CONFIG_SMP + while (current->migration_disabled > saved_mgd_count) + migrate_enable(); +#endif + + while (current->rcu_read_lock_nesting > saved_rcu_count) + rcu_read_unlock(); + WARN_ON_ONCE(current->rcu_read_lock_nesting < saved_rcu_count); +#endif + #ifdef CONFIG_TRACE_IRQFLAGS if (softirq_count()) current->softirqs_enabled = 0; -- cgit v1.2.3