From: Ken Brown <kbrown@cornell.edu>
To: cygwin@cygwin.com
Subject: Re: (call-process ...) hangs in emacs
Date: Thu, 07 Aug 2014 18:54:00 -0000 [thread overview]
Message-ID: <53E3CB46.1020909@cornell.edu> (raw)
In-Reply-To: <53E39BAD.3010004@redhat.com>
On 8/7/2014 11:30 AM, Eric Blake wrote:
> On 08/07/2014 05:51 AM, Ken Brown wrote:
>>
>> I think I found the problem with NORMAL mutexes. emacs calls
>> pthread_atfork after initializing the mutexes, and the resulting
>> 'prepare' handler locks the mutexes. (The parent and child handlers
>> unlock them.) So when emacs calls fork, the mutexes are locked, and
>> shortly thereafter the Cygwin DLL calls calloc, leading to a deadlock.
>> Here's a gdb backtrace showing the sequence of calls:
>
> Arguably, that's an upstream bug in emacs. POSIX has declared
> pthread_atfork to be fundamentally useless; it is broken by design,
> because you cannot use it for anything that is not async-signal-safe
> without risking deadlock. And (except for sem_post()), NONE of the
> standardized locking functions are async-signal-safe.
>
> http://austingroupbugs.net/view.php?id=858
>
> That said, it would still be nice to support this, since even though the
> theory says it is broken, there are still lots of (broken)
> programs/libraries still trying to use it.
So what do you think emacs should do instead of using pthread_atfork?
Or is it better to just remove it? I don't know how likely it is that
this would cause a problem.
Ken
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next prev parent reply other threads:[~2014-08-07 18:54 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-01 12:51 Angelo Graziosi
2014-08-01 13:17 ` Peter Hull
2014-08-01 13:32 ` Corinna Vinschen
2014-08-04 1:03 ` Ken Brown
2014-08-04 8:00 ` Corinna Vinschen
2014-08-04 13:34 ` Ken Brown
2014-08-04 13:45 ` Corinna Vinschen
2014-08-05 12:21 ` Ken Brown
2014-08-05 13:33 ` Peter Hull
2014-08-05 13:59 ` Peter Hull
2014-08-05 13:58 ` Corinna Vinschen
2014-08-05 17:55 ` Ken Brown
2014-08-05 18:40 ` Corinna Vinschen
2014-08-07 11:52 ` Ken Brown
2014-08-07 12:51 ` Corinna Vinschen
2014-08-07 18:54 ` Ken Brown
2014-08-07 15:30 ` Eric Blake
2014-08-07 18:54 ` Ken Brown [this message]
2014-08-07 21:42 ` Eric Blake
2014-08-08 13:27 ` Ken Brown
2014-08-08 15:39 ` Peter Hull
2014-08-09 1:38 ` Ken Brown
2014-08-18 12:28 ` Ken Brown
2014-08-18 14:58 ` Peter Hull
2014-08-18 15:03 ` Larry Hall (Cygwin)
2014-08-25 19:00 ` Ken Brown
2014-08-26 9:13 ` Peter Hull
2014-08-26 18:55 ` Achim Gratz
2014-08-26 22:13 ` Ken Brown
2014-08-27 8:42 ` Corinna Vinschen
2014-08-27 12:53 ` Ken Brown
2014-08-27 13:47 ` Corinna Vinschen
2014-08-27 14:40 ` Eric Blake
2014-08-27 17:15 ` Ken Brown
2014-08-27 15:15 ` Achim Gratz
2014-08-28 7:25 ` Achim Gratz
2014-08-28 9:55 ` Corinna Vinschen
2014-08-28 13:18 ` Corinna Vinschen
2014-08-28 15:04 ` Achim Gratz
2014-08-28 15:10 ` Corinna Vinschen
2014-08-28 15:27 ` Achim Gratz
2014-08-29 9:59 ` Achim Gratz
2014-08-29 11:09 ` Corinna Vinschen
2014-08-29 18:08 ` Ken Brown
2014-08-29 19:23 ` Achim Gratz
2014-08-29 19:36 ` Ken Brown
2014-08-29 20:00 ` Achim Gratz
2014-08-29 21:38 ` Ken Brown
2014-08-29 20:05 ` Andrey Repin
2014-08-29 21:43 ` Corinna Vinschen
2014-08-29 23:35 ` Andrey Repin
2014-09-01 11:47 ` Corinna Vinschen
2014-09-01 11:57 ` Corinna Vinschen
2014-09-01 17:38 ` Achim Gratz
2014-09-02 8:32 ` Corinna Vinschen
2014-09-02 17:29 ` Achim Gratz
2014-09-02 19:19 ` Corinna Vinschen
2014-09-02 19:42 ` Achim Gratz
2014-09-02 20:09 ` Corinna Vinschen
2014-09-02 20:23 ` Achim Gratz
2014-09-03 13:04 ` Corinna Vinschen
2014-09-03 17:59 ` Achim Gratz
2014-08-28 10:34 ` Eric Blake
2014-08-27 21:05 ` Andrey Repin
2014-08-28 10:01 ` Corinna Vinschen
2014-08-28 13:35 ` Andrey Repin
2014-08-28 14:10 ` Corinna Vinschen
2014-08-28 17:05 ` ACL behavior in Cygwin // " Andrey Repin
2014-08-28 18:29 ` Achim Gratz
2014-08-29 8:29 ` Corinna Vinschen
2014-08-28 18:38 ` Achim Gratz
2014-08-28 19:50 ` Andrey Repin
2014-08-06 2:30 ` Katsumi Yamaoka
2014-08-06 8:48 ` Corinna Vinschen
2014-08-06 23:41 ` Katsumi Yamaoka
2014-08-07 0:35 ` Andrey Repin
2014-08-04 8:05 ` Peter Hull
2014-08-04 13:36 ` Ken Brown
-- strict thread matches above, loose matches on Subject: below --
2014-08-06 0:15 Angelo Graziosi
2014-07-31 14:51 Peter Hull
2014-07-31 17:35 ` Ken Brown
2014-08-01 7:36 ` Peter Hull
2014-08-01 10:22 ` Katsumi Yamaoka
2014-08-01 11:33 ` Peter Hull
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