Commit 8946ccc2 authored by Boqun Feng's avatar Boqun Feng Committed by Peter Zijlstra
Browse files

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: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210618170110.3699115-5-boqun.feng@gmail.com
parent 7b1f8c61

lib/locking-selftest.c

+65 −0
Original line number Diff line number Diff line
@@ -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;