Commit ad56450d authored by Boqun Feng's avatar Boqun Feng Committed by Peter Zijlstra
Browse files

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: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-19-boqun.feng@gmail.com
parent 108dc42e

lib/locking-selftest.c

+104 −0
Original line number Diff line number Diff line
@@ -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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