Re: dietlibc (0.31), fork and pthreads

Hi Tim,

I investigated a bit further into the dietlibc libpthread impl.
The problem could be reproduced w/ a vanilla dietlibc-0.32, of course
after patching the makefile for the -fno-stack-protector bug in Ubuntu.

However, if I comment out the call to

__thread_manager_close();
in libpthread/pthread_atfork.c, line 66

Your testcase works like expected (return fds 3,4 before fork,
in child, and in parent). I am not able to explain this properly,
but I am sure that Olaf Dreesen can.

Kind regards

Ingo Struck

On Monday 01 March 2010 13:08:26 Ingo Struck wrote:
> Hi Tim,
>
> > I am compiling with a gcc 4.4.1-4ubuntu0, dietlibc 0.31-1.2ubuntu2, on an
> > x86 machine running ubuntu 9.10.
>
> I can reproduce your problem (w/ proper headers and waitpid call fixed)
> on
>
> ubuntu 8.04.4 LTS, 2.6.24-26-server
> gcc version 4.2.4 (Ubuntu 4.2.4-1ubuntu4)
> diet version 0.31-1ubuntu3
>
> Seems to be a problem in the dietlib libpthread impl.
>
> Maybe you should have a closer look at __thread_manager_close,
> __manager_pipe in libpthread/pthread_internal.c
> and fork() in libpthread/pthread_atfork.c -- it seems that there
> is a call to __thread_manager_close within pid_t fork () in the child
> branch after the __libc_fork() call.
>
> __thread_manager_close calls close() on both mgr_recv_fd and mgr_send_fd
> so maybe something goes wrong there.
>
> Kind regards
>
> Ingo Struck