The following commit has been merged into the locking/core branch of tip: Commit-ID: ad56450db86413ff911eb527b5a49e04a4345e61 Gitweb: https://git.kernel.org/tip/ad56450db86413ff911eb527b5a49e04a4345e61 Author: Boqun Feng <boqun.feng@xxxxxxxxx> AuthorDate: Fri, 07 Aug 2020 15:42:37 +08:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Wed, 26 Aug 2020 12:42:07 +02:00 locking/selftest: Add test cases for queued_read_lock() Add two self test cases for the following case: P0: P1: P2: <in irq handler> spin_lock_irq(&slock) read_lock(&rwlock) write_lock_irq(&rwlock) read_lock(&rwlock) spin_lock(&slock) , which is a deadlock, as the read_lock() on P0 cannot get the lock because of the fairness. P0: P1: P2: <in irq handler> spin_lock(&slock) read_lock(&rwlock) write_lock(&rwlock) read_lock(&rwlock) spin_lock_irq(&slock) , which is not a deadlock, as the read_lock() on P0 can get the lock because it could use the unfair fastpass. Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20200807074238.1632519-19-boqun.feng@xxxxxxxxx --- lib/locking-selftest.c | 104 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 104 insertions(+) diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 4264cf4..17f8f6f 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -2201,6 +2201,108 @@ static void ww_tests(void) pr_cont("\n"); } + +/* + * <in hardirq handler> + * read_lock(&A); + * <hardirq disable> + * spin_lock(&B); + * spin_lock(&B); + * read_lock(&A); + * + * is a deadlock. + */ +static void queued_read_lock_hardirq_RE_Er(void) +{ + HARDIRQ_ENTER(); + read_lock(&rwlock_A); + LOCK(B); + UNLOCK(B); + read_unlock(&rwlock_A); + HARDIRQ_EXIT(); + + HARDIRQ_DISABLE(); + LOCK(B); + read_lock(&rwlock_A); + read_unlock(&rwlock_A); + UNLOCK(B); + HARDIRQ_ENABLE(); +} + +/* + * <in hardirq handler> + * spin_lock(&B); + * <hardirq disable> + * read_lock(&A); + * read_lock(&A); + * spin_lock(&B); + * + * is not a deadlock. + */ +static void queued_read_lock_hardirq_ER_rE(void) +{ + HARDIRQ_ENTER(); + LOCK(B); + read_lock(&rwlock_A); + read_unlock(&rwlock_A); + UNLOCK(B); + HARDIRQ_EXIT(); + + HARDIRQ_DISABLE(); + read_lock(&rwlock_A); + LOCK(B); + UNLOCK(B); + read_unlock(&rwlock_A); + HARDIRQ_ENABLE(); +} + +/* + * <hardirq disable> + * spin_lock(&B); + * read_lock(&A); + * <in hardirq handler> + * spin_lock(&B); + * read_lock(&A); + * + * is a deadlock. Because the two read_lock()s are both non-recursive readers. + */ +static void queued_read_lock_hardirq_inversion(void) +{ + + HARDIRQ_ENTER(); + LOCK(B); + UNLOCK(B); + HARDIRQ_EXIT(); + + HARDIRQ_DISABLE(); + LOCK(B); + read_lock(&rwlock_A); + read_unlock(&rwlock_A); + UNLOCK(B); + HARDIRQ_ENABLE(); + + read_lock(&rwlock_A); + read_unlock(&rwlock_A); +} + +static void queued_read_lock_tests(void) +{ + printk(" --------------------------------------------------------------------------\n"); + printk(" | queued read lock tests |\n"); + printk(" ---------------------------\n"); + print_testname("hardirq read-lock/lock-read"); + dotest(queued_read_lock_hardirq_RE_Er, FAILURE, LOCKTYPE_RWLOCK); + pr_cont("\n"); + + print_testname("hardirq lock-read/read-lock"); + dotest(queued_read_lock_hardirq_ER_rE, SUCCESS, LOCKTYPE_RWLOCK); + pr_cont("\n"); + + print_testname("hardirq inversion"); + dotest(queued_read_lock_hardirq_inversion, FAILURE, LOCKTYPE_RWLOCK); + pr_cont("\n"); +} + void locking_selftest(void) { /* @@ -2318,6 +2420,8 @@ void locking_selftest(void) /* * queued_read_lock() specific test cases can be put here */ + if (IS_ENABLED(CONFIG_QUEUED_RWLOCKS)) + queued_read_lock_tests(); if (unexpected_testcase_failures) { printk("-----------------------------------------------------------------\n");
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