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X-HELO: calimero.vinschen.de
Date: Wed, 25 Feb 2015 18:51:49 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Unexpected EINVAL from pthread_join
Message-ID: <20150225175149.GR437@calimero.vinschen.de>
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On Feb 24 22:20, Corinna Vinschen wrote:
> Hi Lasse,
>=20
> On Feb 24 20:37, Lasse Collin wrote:
> > On 2015-02-24 Corinna Vinschen wrote:
> > > On Feb 24 15:54, Lasse Collin wrote:
> > > > Many other pthread functions are similar in sense that they must
> > > > never return EINTR. A bug similar to the one in pthread::join exist
> > > > in pthread_mutex::lock. If SA_RESTART isn't used, signals can make
> > > > multiple threads get a lock on the same mutex at the same time. A
> > > > test program is attached. Adding cw_sig_restart to the cygwait call
> > > > in pthread_mutex::lock fixes this.
> > >=20
> > > Can you collect the info which functions are affected so that lazy me
> > > just has to apply the cw_sig_restart patches in bulk?
> >=20
> > I grepped for cygwait uses earlier but I don't understand the code well
> > enough to be sure about anything. The following is pretty much
> > guessing, but hopefully there's something useful still.
> >=20
> > These look the most suspicious to me, possibly needing cw_sig_restart:
> >=20
> >     thread.h          fast_mutex::lock
> >     fhandler_tape.cc  fhandler_dev_tape::_lock

FYI, I fixed these plus pthread_mutex::lock.

> > When looking for things needing cw_sig_restart, I started to wonder if
> > cw_sig_eintr is used properly in all cases. Often the caller of
> > cygwait + cw_sig_eintr will also conditionally call
> > _my_tls.call_signal_handler, but the following functions don't. The
> > comment in handle_sigsuspend makes me think that this may be a false
> > alarm but I mention these just in case.
> >=20
> >     exceptions.cc     handle_sigsuspend

This works as desired, afaics.

> >     posix_ipc.cc      ipc_mutex_lock
> >     signal.cc         clock_nanosleep
> >     signal.cc         sigwaitinfo
> >     thread.cc         pthread_cond::wait
> >     thread.cc         semaphore::_timedwait
> >     thread.cc         semaphore::_wait
> [...]
> > In the following functions the situation is kind of reversed. Those
> > functions call _my_tls.call_signal_handler even though cw_sig_eintr
> > wasn't specified. cygwait will already have called the signal handler
> > since cw_sig has been specified via cygwait(DWORD). So I guess in these
> > functions the signal handler might get called twice.
> >=20
> >     fhandler_dsp.cc   fhandler_dev_dsp::Audio_out::waitforspace
> >     fhandler_dsp.cc   fhandler_dev_dsp::Audio_in::waitfordata

I'm still mulling over the rest of your list...


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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