Subject: [Bug 203647] Locking API testsuite fails "mixed read-lock/lock-write ABBA" rlock on kernels >=4.14.x

From: [email-masked]
Date: Tue, 21 May 2019 05:35:22 +0000

https://bugzilla.kernel.org/show_bug.cgi?id=203647

Michael Ellerman ([email-masked]) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            [email-masked]
         Resolution|---                         |DOCUMENTED

--- Comment #6 from Michael Ellerman ([email-masked]) ---
This appears to be working as expected, which I admit is a little confusing.

The key thing is that at the end you see, eg:

  [    0.179788] Good, all 261 testcases passed! |

See the commit that added the test:

https://git.kernel.org/torvalds/c/e91498589746

  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.

And in the code:

        print_testname("mixed read-lock/lock-write ABBA");
        pr_cont("             |");
        dotest(rlock_ABBA1, FAILURE, LOCKTYPE_RWLOCK);
#ifdef CONFIG_PROVE_LOCKING
        /*
         * Lockdep does indeed fail here, but there's nothing we can do about
         * that now.  Don't kill lockdep for it.
         */
        unexpected_testcase_failures--;
#endif

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