As our chain cache doesn't differ read/write locks, so even we can
detect a read-lock/lock-write deadlock in check_noncircular(), we can
still be fooled if a read-lock/lock-read case(which is not a deadlock)
comes first.
So introduce this test case to test specific to the chain cache behavior
on detecting recursive read lock related deadlocks.
Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
---
lib/locking-selftest.c | 47 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)
diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index caadc4dd3368..002d1ec09852 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -396,6 +396,49 @@ static void rwsem_ABBA1(void)
MU(Y1); // should fail
}
+/*
+ * read_lock(A)
+ * spin_lock(B)
+ * spin_lock(B)
+ * write_lock(A)
+ *
+ * This test case is aimed at poking whether the chain cache prevents us from
+ * detecting a read-lock/lock-write deadlock: if the chain cache doesn't differ
+ * read/write locks, the following case may happen
+ *
+ * { read_lock(A)->lock(B) dependency exists }
+ *
+ * P0:
+ * lock(B);
+ * read_lock(A);
+ *
+ * { Not a deadlock, B -> A is added in the chain cache }
+ *
+ * P1:
+ * lock(B);
+ * write_lock(A);
+ *
+ * { B->A found in chain cache, not reported as a deadlock }
+ *
+ */
+static void rlock_chaincache_ABBA1(void)
+{
+ RL(X1);
+ L(Y1);
+ U(Y1);
+ RU(X1);
+
+ L(Y1);
+ RL(X1);
+ RU(X1);
+ U(Y1);
+
+ L(Y1);
+ WL(X1);
+ WU(X1);
+ U(Y1); // should fail
+}
+
/*
* read_lock(A)
* spin_lock(B)
@@ -2062,6 +2105,10 @@ void locking_selftest(void)
pr_cont(" |");
dotest(rwsem_ABBA3, FAILURE, LOCKTYPE_RWSEM);
+ print_testname("chain cached mixed R-L/L-W ABBA");
+ pr_cont(" |");
+ dotest(rlock_chaincache_ABBA1, FAILURE, LOCKTYPE_RWLOCK);
+
printk(" --------------------------------------------------------------------------\n");
/*
--
2.28.0
