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: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201102053743.450459-2-boqun.feng@gmail.com

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index afa7d4bb291f46d80e10b9239abed9698de44c7a..4c24ac8a456c4c1bcc38ee71b2c68fa5c30eff54 100644 (file)
--- 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");