[PATCH 2/4] test-ww_mutex: Report errors from stress workers

["Håkon Bugge" <haakon.bugge@oracle.com>]

If any of stress_one_work(), stress_reorder_work(), or
stress_inorder_work() fails, the error is not conveyed back to the
test harness function stress().

We may then see in the log:

   stress (stress_inorder_work) failed with -35
   Beginning ww (die) mutex selftests
   All ww mutex selftests passed

Besides being a contradiction by terms, the failure to return error
from said worker functions leads to false-positive results.

We fix that by adding a *result* variable to *struct stress*, update
it in said worker functions, and finally, in stress(), scan the
*stress_array* and report the first error if any.

Fixes: 2a0c11282881 ("locking/ww_mutex: Add kselftests for ww_mutex stress")
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
---
 kernel/locking/test-ww_mutex.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 6f56a29ed6d77..5a4c92801bdfb 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -392,6 +392,7 @@ struct stress {
 	struct ww_class *class;
 	unsigned long timeout;
 	int nlocks;
+	int result;
 };
 
 struct rnd_state rng;
@@ -440,6 +441,9 @@ static void stress_inorder_work(struct work_struct *work)
 	struct ww_mutex *locks = stress->locks;
 	struct ww_acquire_ctx ctx;
 	int *order;
+	int err;
+
+	stress->result = -ENOMEM;
 
 	order = get_random_order(nlocks);
 	if (!order)
@@ -447,7 +451,7 @@ static void stress_inorder_work(struct work_struct *work)
 
 	do {
 		int contended = -1;
-		int n, err;
+		int n;
 
 		ww_acquire_init(&ctx, stress->class);
 retry:
@@ -485,6 +489,7 @@ static void stress_inorder_work(struct work_struct *work)
 	} while (!time_after(jiffies, stress->timeout));
 
 	kfree(order);
+	stress->result = err;
 }
 
 struct reorder_lock {
@@ -501,6 +506,8 @@ static void stress_reorder_work(struct work_struct *work)
 	int *order;
 	int n, err;
 
+	stress->result = -ENOMEM;
+
 	order = get_random_order(stress->nlocks);
 	if (!order)
 		return;
@@ -545,6 +552,8 @@ static void stress_reorder_work(struct work_struct *work)
 		ww_acquire_fini(&ctx);
 	} while (!time_after(jiffies, stress->timeout));
 
+	stress->result = err;
+
 out:
 	list_for_each_entry_safe(ll, ln, &locks, link)
 		kfree(ll);
@@ -569,6 +578,8 @@ static void stress_one_work(struct work_struct *work)
 			break;
 		}
 	} while (!time_after(jiffies, stress->timeout));
+
+	stress->result = err;
 }
 
 #define STRESS_INORDER BIT(0)
@@ -581,6 +592,7 @@ static int stress(struct ww_class *class, int nlocks, int nthreads, unsigned int
 	struct ww_mutex *locks;
 	struct stress *stress_array;
 	int n, count;
+	int res = 0;
 
 	locks = kmalloc_objs(*locks, nlocks);
 	if (!locks)
@@ -635,10 +647,15 @@ static int stress(struct ww_class *class, int nlocks, int nthreads, unsigned int
 
 	for (n = 0; n < nlocks; n++)
 		ww_mutex_destroy(&locks[n]);
+
+	/* Report the first error */
+	for (n = 0; !res && n < count; n++)
+		res = stress_array[n].result;
+
 	kfree(stress_array);
 	kfree(locks);
 
-	return 0;
+	return res;
 }
 
 static int run_tests(struct ww_class *class)
-- 
2.43.5