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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 45248] testlockperf of apr_thread_rwlock_t stalls forever on i686 Linux / glibc 2 .7
Date Wed, 02 Jul 2008 07:18:37 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=45248


Nix <nix@esperi.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |INVALID




--- Comment #18 from Nix <nix@esperi.org.uk>  2008-07-02 00:18:36 PST ---
No, it still fails. Thus it's not APR at fault.

... interesting. Adding a heap of write() calls shows:

Main
Main got lock
Thread
Thread
Thread
Main made threads
Thread got lock; thread released lock
[~10000 repetitions of the above two lines]
Thread released lock
Main released lock
ead released lock
Thread got lock; thread released lock
[~1.1 million repetitions of the above two lines]
[Hang]

Upon deadlock the rwlock says

__lock = 0, __nr_readers = 0, __readers_wakeup = 0, __writer_wakeup = 219178,
__nr_readers_queued = 0, __nr_writers_queued = 0, __flags = 0 '\0', __shared =
0 '\0', __pad1 = 0 '\0', __pad2 = 0 '\0', __writer = 0

i.e. it shouldn't be blocking (no readers, not locked nothing queued).

I think it's plain that pthread_rwlocks are not, well, locking, at least not
for me (although they deadlock fine), and that this cannot be blamed on APR.

Sorry for wasting your time. I'll dig into glibc's rwlock implementation and
see if any fixes have been made upstream since glibc 2.7.


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