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@xxxxxxxxxxxxxxxxxxxxx/ Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> --- lib/locking-selftest.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index afa7d4bb291f..4c24ac8a456c 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -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"); -- 2.28.0
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