diff mbox series

[3/3] test-ww_mutex: Make sure we bail out instead of livelock

Message ID 20230922043616.19282-4-jstultz@google.com
State New
Headers
Series Fixes for test-ww_mutex stress test |

Commit Message

John Stultz Sept. 22, 2023, 4:36 a.m. UTC 
  I've seen what appears to be livelocks in the stress_inorder_work()
function, and looking at the code it is clear we can have a case
where we continually retry acquiring the locks and never check to
see if we have passed the specified timeout.

This patch reworks that function so we always check the timeout
before iterating through the loop again.

I believe others may have hit this previously here:
https://lore.kernel.org/lkml/895ef450-4fb3-5d29-a6ad-790657106a5a@intel.com/

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: kernel-team@android.com
Reported-by: Li Zhijian <zhijianx.li@intel.com>
Link: https://lore.kernel.org/lkml/895ef450-4fb3-5d29-a6ad-790657106a5a@intel.com/
Signed-off-by: John Stultz <jstultz@google.com>
---
 kernel/locking/test-ww_mutex.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index 358d66150426..78719e1ef1b1 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -465,17 +465,18 @@  static void stress_inorder_work(struct work_struct *work)
 			ww_mutex_unlock(&locks[order[n]]);
 
 		if (err == -EDEADLK) {
-			ww_mutex_lock_slow(&locks[order[contended]], &ctx);
-			goto retry;
+			if (!time_after(jiffies, stress->timeout)) {
+				ww_mutex_lock_slow(&locks[order[contended]], &ctx);
+				goto retry;
+			}
 		}
 
+		ww_acquire_fini(&ctx);
 		if (err) {
 			pr_err_once("stress (%s) failed with %d\n",
 				    __func__, err);
 			break;
 		}
-
-		ww_acquire_fini(&ctx);
 	} while (!time_after(jiffies, stress->timeout));
 
 	kfree(order);