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locking/ww_mutex/test: Make sure we bail out instead of livelock

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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/

Reported-by: Li Zhijian <zhijianx.li@intel.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230922043616.19282-4-jstultz@google.com
This commit is contained in:
John Stultz 2023-09-22 04:36:01 +00:00 committed by Ingo Molnar
parent bccdd80890
commit cfa92b6d52
1 changed files with 5 additions and 4 deletions
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9
kernel/locking/test-ww_mutex.c
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@ -465,17 +465,18 @@ retry:
ww_mutex_unlock(&locks[order[n]]); ww_mutex_unlock(&locks[order[n]]);
if (err == -EDEADLK) { if (err == -EDEADLK) {
ww_mutex_lock_slow(&locks[order[contended]], &ctx); if (!time_after(jiffies, stress->timeout)) {
goto retry; ww_mutex_lock_slow(&locks[order[contended]], &ctx);
goto retry;
}
} }
ww_acquire_fini(&ctx);
if (err) { if (err) {
pr_err_once("stress (%s) failed with %d\n", pr_err_once("stress (%s) failed with %d\n",
__func__, err); __func__, err);
break; break;
} }
ww_acquire_fini(&ctx);
} while (!time_after(jiffies, stress->timeout)); } while (!time_after(jiffies, stress->timeout));
kfree(order); kfree(order);