Commit e9149858 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

locking/lockdep/selftests: Add mixed read-write ABBA tests 



Currently lockdep has limited support for recursive readers, add a few
mixed read-write ABBA selftests to show the extend of these
limitations.

  [    0.000000] ----------------------------------------------------------------------------
  [    0.000000]                                  | spin |wlock |rlock |mutex | wsem | rsem |
  [    0.000000]   --------------------------------------------------------------------------

  [    0.000000]   mixed read-lock/lock-write ABBA:             |FAILED|             |  ok  |
  [    0.000000]    mixed read-lock/lock-read ABBA:             |  ok  |             |  ok  |
  [    0.000000]  mixed write-lock/lock-write ABBA:             |  ok  |             |  ok  |

This clearly illustrates the case where lockdep fails to find a
deadlock.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: byungchul.park@lge.com
Cc: david@fromorbit.com
Cc: johannes@sipsolutions.net
Cc: oleg@redhat.com
Cc: tj@kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0e709703

lib/locking-selftest.c

+115 −2
Original line number Diff line number Diff line
@@ -362,6 +362,103 @@ static void rsem_AA3(void) 
	RSL(X2); // this one should fail

}



/*

 * read_lock(A)

 * spin_lock(B)

 *		spin_lock(B)

 *		write_lock(A)

 */

static void rlock_ABBA1(void)

{

	RL(X1);

	L(Y1);

	U(Y1);

	RU(X1);



	L(Y1);

	WL(X1);

	WU(X1);

	U(Y1); // should fail

}



static void rwsem_ABBA1(void)

{

	RSL(X1);

	ML(Y1);

	MU(Y1);

	RSU(X1);



	ML(Y1);

	WSL(X1);

	WSU(X1);

	MU(Y1); // should fail

}



/*

 * read_lock(A)

 * spin_lock(B)

 *		spin_lock(B)

 *		read_lock(A)

 */

static void rlock_ABBA2(void)

{

	RL(X1);

	L(Y1);

	U(Y1);

	RU(X1);



	L(Y1);

	RL(X1);

	RU(X1);

	U(Y1); // should NOT fail

}



static void rwsem_ABBA2(void)

{

	RSL(X1);

	ML(Y1);

	MU(Y1);

	RSU(X1);



	ML(Y1);

	RSL(X1);

	RSU(X1);

	MU(Y1); // should fail

}





/*

 * write_lock(A)

 * spin_lock(B)

 *		spin_lock(B)

 *		write_lock(A)

 */

static void rlock_ABBA3(void)

{

	WL(X1);

	L(Y1);

	U(Y1);

	WU(X1);



	L(Y1);

	WL(X1);

	WU(X1);

	U(Y1); // should fail

}



static void rwsem_ABBA3(void)

{

	WSL(X1);

	ML(Y1);

	MU(Y1);

	WSU(X1);



	ML(Y1);

	WSL(X1);

	WSU(X1);

	MU(Y1); // should fail

}



/*

 * ABBA deadlock:

 */
@@ -1056,8 +1153,6 @@ static void dotest(void (*testcase_fn)(void), int expected, int lockclass_mask) 
	if (debug_locks != expected) {

		unexpected_testcase_failures++;

		pr_cont("FAILED|");



		dump_stack();

	} else {

		testcase_successes++;

		pr_cont("  ok  |");
@@ -1933,6 +2028,24 @@ void locking_selftest(void) 
	dotest(rsem_AA3, FAILURE, LOCKTYPE_RWSEM);

	pr_cont("\n");



	print_testname("mixed read-lock/lock-write ABBA");

	pr_cont("             |");

	dotest(rlock_ABBA1, FAILURE, LOCKTYPE_RWLOCK);

	pr_cont("             |");

	dotest(rwsem_ABBA1, FAILURE, LOCKTYPE_RWSEM);



	print_testname("mixed read-lock/lock-read ABBA");

	pr_cont("             |");

	dotest(rlock_ABBA2, SUCCESS, LOCKTYPE_RWLOCK);

	pr_cont("             |");

	dotest(rwsem_ABBA2, FAILURE, LOCKTYPE_RWSEM);



	print_testname("mixed write-lock/lock-write ABBA");

	pr_cont("             |");

	dotest(rlock_ABBA3, FAILURE, LOCKTYPE_RWLOCK);

	pr_cont("             |");

	dotest(rwsem_ABBA3, FAILURE, LOCKTYPE_RWSEM);



	printk("  --------------------------------------------------------------------------\n");



	/*

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