locking/selftests: Add a selftest for check_irq_usage()

Johannes Berg reported a lockdep problem which could be reproduced by
the special test case introduced in this patch, so add it.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210618170110.3699115-5-boqun.feng@gmail.com

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 2d85abac17448aa5df78203ba07148c537998e66..5c50b091039634c3c77dcef46c85a701a631be34 100644 (file)
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -53,6 +53,7 @@ __setup("debug_locks_verbose=", setup_debug_locks_verbose);
 #define LOCKTYPE_WW    0x10
 #define LOCKTYPE_RTMUTEX 0x20
 #define LOCKTYPE_LL    0x40
+#define LOCKTYPE_SPECIAL 0x80
 
 static struct ww_acquire_ctx t, t2;
 static struct ww_mutex o, o2, o3;
@@ -2744,6 +2745,66 @@ static void local_lock_tests(void)
        pr_cont("\n");
 }
 
+static void hardirq_deadlock_softirq_not_deadlock(void)
+{
+       /* mutex_A is hardirq-unsafe and softirq-unsafe */
+       /* mutex_A -> lock_C */
+       mutex_lock(&mutex_A);
+       HARDIRQ_DISABLE();
+       spin_lock(&lock_C);
+       spin_unlock(&lock_C);
+       HARDIRQ_ENABLE();
+       mutex_unlock(&mutex_A);
+
+       /* lock_A is hardirq-safe */
+       HARDIRQ_ENTER();
+       spin_lock(&lock_A);
+       spin_unlock(&lock_A);
+       HARDIRQ_EXIT();
+
+       /* lock_A -> lock_B */
+       HARDIRQ_DISABLE();
+       spin_lock(&lock_A);
+       spin_lock(&lock_B);
+       spin_unlock(&lock_B);
+       spin_unlock(&lock_A);
+       HARDIRQ_ENABLE();
+
+       /* lock_B -> lock_C */
+       HARDIRQ_DISABLE();
+       spin_lock(&lock_B);
+       spin_lock(&lock_C);
+       spin_unlock(&lock_C);
+       spin_unlock(&lock_B);
+       HARDIRQ_ENABLE();
+
+       /* lock_D is softirq-safe */
+       SOFTIRQ_ENTER();
+       spin_lock(&lock_D);
+       spin_unlock(&lock_D);
+       SOFTIRQ_EXIT();
+
+       /* And lock_D is hardirq-unsafe */
+       SOFTIRQ_DISABLE();
+       spin_lock(&lock_D);
+       spin_unlock(&lock_D);
+       SOFTIRQ_ENABLE();
+
+       /*
+        * mutex_A -> lock_C -> lock_D is softirq-unsafe -> softirq-safe, not
+        * deadlock.
+        *
+        * lock_A -> lock_B -> lock_C -> lock_D is hardirq-safe ->
+        * hardirq-unsafe, deadlock.
+        */
+       HARDIRQ_DISABLE();
+       spin_lock(&lock_C);
+       spin_lock(&lock_D);
+       spin_unlock(&lock_D);
+       spin_unlock(&lock_C);
+       HARDIRQ_ENABLE();
+}
+
 void locking_selftest(void)
 {
        /*
@@ -2872,6 +2933,10 @@ void locking_selftest(void)
 
        local_lock_tests();
 
+       print_testname("hardirq_unsafe_softirq_safe");
+       dotest(hardirq_deadlock_softirq_not_deadlock, FAILURE, LOCKTYPE_SPECIAL);
+       pr_cont("\n");
+
        if (unexpected_testcase_failures) {
                printk("-----------------------------------------------------------------\n");
                debug_locks = 0;