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From venkatnv <venka...@yahoo.com>
Subject Re: Posix sems still not recommended?
Date Fri, 24 Apr 2009 02:33:59 GMT

We are observing issues with pthread Mutexes on Apache22/Solaris10. Not sure
if this is relevant to this thread, but would appreciate any  inputs.

- We are running Apache22 in Worker mode. Apache22 is compiled with gcc346
on Solaris10
- We are having a custom module (DSO) loaded with Apache.

On stress test, we see that a mutex is not working as intended.
To be precise, we are seeing core dumps and further investigation revealed
that there are two threads that have acquired a lock using
pthread_mutex_lock, a the same time. 

Please note that we do not see this behavior on Apache2. This occurs only
with Apache22. Has anyone come across a similar situation. Any help in
narrowing down the cause would be greatly appreciated!


Rainer Jung-3 wrote:
> On 30.03.2009 20:58, Jeff Trawick wrote:
>> On Mon, Mar 30, 2009 at 2:33 PM, Jeff Trawick <trawick@gmail.com
>> <mailto:trawick@gmail.com>> wrote:
>> On Mon, Mar 30, 2009 at 2:07 PM, Jim Jagielski <jim@jagunet.com
>> <mailto:jim@jagunet.com>> wrote:
>> Anyone know if:
>> # POSIX semaphores and cross-process pthread mutexes are not # used
>> by default since they have less desirable behaviour when # e.g. a
>> process holding the mutex segfaults.
>> is still applicable, at least for posix sems?
>> AFAIK, the Solaris-specific recovery logic for cross-process pthread
>> mutexes has been working reliably for a long time, but with the
>> current wind direction APR is choosing fcntl(), which has sysdef
>> implementations on that
>> ugh; "sysdef implications"
> and quite often shows EDEADLOCK, even when you can prove there can't be
> one. Especially when starting to use more than one lock of that type
> (e.g. when SSL comes into the game).
>> platform.
>> no clues here about the POSIX semaphores
> I would be much interested in an answer as well. Because of the
> EDEADLOCK problems I did suggest using the pthread based mutex on
> Solaris for a while to people and got no problem reports. But what
> experience do others have?
> In a related thread on the Tomcat users list about mod_jk I wrote in
> February:
>    I now did some searching and it turns out that the implementation of
>    pthread mutexes for Solaris 10 has very recently changed quite a bit.
>    So all speculations about improved pthread mutex behaviour
>    (especially for "robust" mutexes) in the last years might have become
>    obsolete.
>    The new implementation is contained in Solaris kernel patch 137137-09
>    and most likely also in Solaris 10 Update 6 (10/08). I didn't check,
>    whether that update simply contains the kernel patch or the fix is
>    included independently.
>    Some detail is logged in Sunsolve under the bug IDs
>    6296770 2160259 6664275 6697344 6729759 6564706
> Regards,
> Rainer

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