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Date:	Tue, 28 Jan 2025 09:57:26 +0100
To:	cygwin AT cygwin DOT com
Subject:	Re: mq_send()/mq_receive() may never return if used from threads
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From:	Corinna Vinschen via Cygwin <cygwin AT cygwin DOT com>
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Cc:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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On Jan 28 09:00, Christian Franke via Cygwin wrote:
> Corinna Vinschen via Cygwin wrote:
> > On Jan 27 20:35, Corinna Vinschen via Cygwin wrote:
> > > On Jan 27 19:59, Christian Franke via Cygwin wrote:
> > > > Christian Franke wrote:
> > > > > Found with 'stress-ng --workload ...':
> > > > > 
> > > > > If mq_receive is called on an empty queue and mq_send is called later
> > > > > from a different thread, both functions never return and signals
> > > > > (including SIGKILL) are no longer processed.
> > > > > 
> > > > > Testcase (attached):
> > > > > 
> > > > > $ uname -r
> > > > > 3.5.5-1.x86_64
> > > > > 
> > > > The problem is also reproducible with 3.5.6-1 and recent
> > > > 3.6.0-0.345.gb940faa144ca
> > > Yes, because I didn't have the time to look into it yet.
> > > 
> > > I just did, and I think I see what's going on.  This should be fixed
> > > in 3.5.7.
> > I just pushed a patch, please try cygwin-3.6.0-0.346.gfe6ddc15a356.
> 
> $ uname -r
> 3.6.0-0.346.gfe6ddc15a356.x86_64
> 
> $ time ./mqhang
> mq_send...
> mq_send = 0
> mq_receive...
> mq_receive = 8
> mq_receive...
> mq_send...
> mq_receive = 8
> mq_send = 0
> 
> real    0m5.002s
> user    0m0.000s
> sys     0m0.000s
> 
> $ stress-ng --workload 16 --timeout 60 --verify
> stress-ng: info:  [4873] setting to a 1 min run per stressor
> stress-ng: info:  [4873] dispatching hogs: 16 workload
> stress-ng: info:  [4874] workload: running with 2 threads per stressor
> instance
> stress-ng: info:  [4873] skipped: 0
> stress-ng: info:  [4873] passed: 16: workload (16)
> stress-ng: info:  [4873] failed: 0
> stress-ng: info:  [4873] metrics untrustworthy: 0
> stress-ng: info:  [4873] successful run completed in 1 min, 3.31 secs
> 
> Looks good!

Cool, thanks for testing.  I guess I release a 3.5.7 pretty soon.


Thanks,
Corinna

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