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Re: [1.7] flock change breaks autotools 'make -j2'
- From: Corinna Vinschen <corinna-cygwin at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Fri, 17 Apr 2009 12:01:48 +0200
- Subject: Re: [1.7] flock change breaks autotools 'make -j2'
- References: <loom.20090416T201917-225@post.gmane.org>
- Reply-to: cygwin at cygwin dot com
On Apr 16 20:39, Eric Blake wrote:
> This change in cygwin 1.7:
>
> - File locking is now advisory, not mandatory anymore. The fcntl(2) and
> the new lockf(2) APIs create and maintain locks with POSIX semantics,
> the flock(2) API creates and maintains locks with BSD semantics.
> POSIX and BSD locks are independent of each other.
>
> is causing parallel make bugs in autotooled projects:
>
> http://lists.gnu.org/archive/html/bug-automake/2009-04/msg00048.html
>
> The problem is that perl's flock is no longer locking files the way it
> used to, so parallel instances of autom4te (the engine behind both
> autoconf and automake) end up stomping on each others' output. I
> don't know if it something that needs to be fixed in perl, in
> automake's XFile::lock wrapper around perl's flock, or even in cygwin
> itself. But it seems like if two instances of the same perl program
> are using the same advisory locking mechanism, that they should keep
> each other out of the file properly (advisory means that processes not
> using flock can still stomp on the file, but not other processes using
> the same locking mechanism).
Default question: Do you have a simple testcase to reproduce this
problem? I'm going to play with the lock.pl perl script from
http://lists.gnu.org/archive/html/bug-automake/2009-04/msg00053.html but
I don't know if I can get it working. Perl isn't exactly my domain.
I'd prefer a testcase in C.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
Red Hat
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