Commit e04ce676 authored by Boqun Feng's avatar Boqun Feng Committed by Peter Zijlstra
Browse files

lockdep/selftest: Add spin_nest_lock test 

Add a self test case to test the behavior for the following case:

	lock(A);
	lock_nest_lock(C1, A);
	lock(B);
	lock_nest_lock(C2, A);

This is a reproducer for a problem[1] reported by Chris Wilson, and is
helpful to prevent this.

[1]: https://lore.kernel.org/lkml/160390684819.31966.12048967113267928793@build.alporthouse.com/



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/20201102053743.450459-2-boqun.feng@gmail.com
parent a2e9ae58

lib/locking-selftest.c

+17 −0
Original line number Diff line number Diff line
@@ -2009,6 +2009,19 @@ static void ww_test_spin_nest_unlocked(void) 
	U(A);

}



/* This is not a deadlock, because we have X1 to serialize Y1 and Y2 */

static void ww_test_spin_nest_lock(void)

{

	spin_lock(&lock_X1);

	spin_lock_nest_lock(&lock_Y1, &lock_X1);

	spin_lock(&lock_A);

	spin_lock_nest_lock(&lock_Y2, &lock_X1);

	spin_unlock(&lock_A);

	spin_unlock(&lock_Y2);

	spin_unlock(&lock_Y1);

	spin_unlock(&lock_X1);

}



static void ww_test_unneeded_slow(void)

{

	WWAI(&t);
@@ -2226,6 +2239,10 @@ static void ww_tests(void) 
	dotest(ww_test_spin_nest_unlocked, FAILURE, LOCKTYPE_WW);

	pr_cont("\n");



	print_testname("spinlock nest test");

	dotest(ww_test_spin_nest_lock, SUCCESS, LOCKTYPE_WW);

	pr_cont("\n");



	printk("  -----------------------------------------------------\n");

	printk("                                 |block | try  |context|\n");

	printk("  -----------------------------------------------------\n");