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bug#10641: [2.0.3+] start_signal_delivery_thread failure on x86_64-freeb
From: |
Ludovic Courtès |
Subject: |
bug#10641: [2.0.3+] start_signal_delivery_thread failure on x86_64-freebsd8.2 |
Date: |
Fri, 29 Mar 2013 10:49:41 +0100 |
User-agent: |
Gnus/5.130005 (Ma Gnus v0.5) Emacs/24.3 (gnu/linux) |
Andy Wingo <address@hidden> skribis:
> On Sun 29 Jan 2012 19:00, address@hidden (Ludovic Courtès) writes:
>
>> Adding printfs shows that the thread calling scm_spawn_thread leaves
>> cond_wait before the signal thread has signaled the condition (in
>> really_spawn).
>
> From
> http://pubs.opengroup.org/onlinepubs/009604599/functions/pthread_cond_wait.html
>
> When using condition variables there is always a Boolean predicate
> involving shared variables associated with each condition wait that is
> true if the thread should proceed. Spurious wakeups from the
> pthread_cond_timedwait() or pthread_cond_wait() functions may
> occur. Since the return from pthread_cond_timedwait() or
> pthread_cond_wait() does not imply anything about the value of this
> predicate, the predicate should be re-evaluated upon such return.
>
> It seems this code is not robust in the face of spurious wakeups. I
> pushed a patch that waits for data.thread to become non-false. That
> should fix this issue.
Good catch, and congratulations! I can confirm that this fixes
--with-thread builds on FreeBSD 8.2:
http://hydra.nixos.org/build/4519811
Thanks!
Ludo’.