[tip:locking/core] tools/lib/lockdep: Add tests for AA and ABBA locking

[tip-bot for Alfredo Alvarez Fernandez]

Commit-ID:  11a1ac206d0806b0db39712c3292f6006e77a7e8
Gitweb:     http://git.kernel.org/tip/11a1ac206d0806b0db39712c3292f6006e77a7e8
Author:     Alfredo Alvarez Fernandez <alfredoalvarezfernandez@xxxxxxxxx>
AuthorDate: Fri, 19 Feb 2016 07:48:52 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 29 Feb 2016 10:29:33 +0100

tools/lib/lockdep: Add tests for AA and ABBA locking

Add test for AA and 2 threaded ABBA locking.

Rename AA.c to ABA.c since it was implementing an ABA instead of a pure
AA. Now both cases are covered.

The expected output for AA.c is that the process blocks and lockdep
reports a deadlock.

ABBA_2threads.c differs from ABBA.c in that lockdep keeps separate chains
of held locks per task. This can lead to different behaviour regarding
lock detection. The expected output for this test is that the process
blocks and lockdep reports a circular locking dependency.

These tests found a lockdep bug - fixed by the next commit.

Signed-off-by: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1455864533-7536-3-git-send-email-alfredoalvarezernandez@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 tools/lib/lockdep/tests/AA.c            |  8 +++---
 tools/lib/lockdep/tests/{AA.c => ABA.c} |  0
 tools/lib/lockdep/tests/ABBA_2threads.c | 46 +++++++++++++++++++++++++++++++++
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/tools/lib/lockdep/tests/AA.c b/tools/lib/lockdep/tests/AA.c
index 0f782ff..18211a5 100644
--- a/tools/lib/lockdep/tests/AA.c
+++ b/tools/lib/lockdep/tests/AA.c
@@ -1,13 +1,13 @@
 #include <liblockdep/mutex.h>
 
-void main(void)
+int main(void)
 {
-	pthread_mutex_t a, b;
+	pthread_mutex_t a;
 
 	pthread_mutex_init(&a, NULL);
-	pthread_mutex_init(&b, NULL);
 
 	pthread_mutex_lock(&a);
-	pthread_mutex_lock(&b);
 	pthread_mutex_lock(&a);
+
+	return 0;
 }
diff --git a/tools/lib/lockdep/tests/AA.c b/tools/lib/lockdep/tests/ABA.c
similarity index 100%
copy from tools/lib/lockdep/tests/AA.c
copy to tools/lib/lockdep/tests/ABA.c
diff --git a/tools/lib/lockdep/tests/ABBA_2threads.c b/tools/lib/lockdep/tests/ABBA_2threads.c
new file mode 100644
index 0000000..cd807d7
--- /dev/null
+++ b/tools/lib/lockdep/tests/ABBA_2threads.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <pthread.h>
+
+pthread_mutex_t a = PTHREAD_MUTEX_INITIALIZER;
+pthread_mutex_t b = PTHREAD_MUTEX_INITIALIZER;
+pthread_barrier_t bar;
+
+void *ba_lock(void *arg)
+{
+	int ret, i;
+
+	pthread_mutex_lock(&b);
+
+	if (pthread_barrier_wait(&bar) == PTHREAD_BARRIER_SERIAL_THREAD)
+		pthread_barrier_destroy(&bar);
+
+	pthread_mutex_lock(&a);
+
+	pthread_mutex_unlock(&a);
+	pthread_mutex_unlock(&b);
+}
+
+int main(void)
+{
+	pthread_t t;
+
+	pthread_barrier_init(&bar, NULL, 2);
+
+	if (pthread_create(&t, NULL, ba_lock, NULL)) {
+		fprintf(stderr, "pthread_create() failed\n");
+		return 1;
+	}
+	pthread_mutex_lock(&a);
+
+	if (pthread_barrier_wait(&bar) == PTHREAD_BARRIER_SERIAL_THREAD)
+		pthread_barrier_destroy(&bar);
+
+	pthread_mutex_lock(&b);
+
+	pthread_mutex_unlock(&b);
+	pthread_mutex_unlock(&a);
+
+	pthread_join(t, NULL);
+
+	return 0;
+}