Re: Robust shared mutexes?

[Szabolcs Nagy <nsz@port70.net>]

* Sebastian Kemper <sebastian_ml@gmx.net> [2016-11-27 11:54:34 +0100]:
> On Sun, Nov 27, 2016 at 12:01:10AM +0100, Szabolcs Nagy wrote:
> > * Rich Felker <dalias@libc.org> [2016-11-26 17:56:18 -0500]:
> > > On Sat, Nov 26, 2016 at 11:51:05PM +0100, Sebastian Kemper wrote:
> > > > 
> > > > http://lists.openembedded.org/pipermail/openembedded-core/2016-March/119214.html
> > > > 
> > > > It says musl doesn't have process shared mutexes so one should set
> > > > apr_cv_process_shared_works=no. I take it that is correct?
> > > 
> > > No, it's incorrect and I have no idea where that idea came from. I'll
> > > ask Khem.
> > > 
> > 
> > apr might care about sharing mutexes across i386 vs x86_64 ?
> > 
> > that does not work (glibc ditto)
> 
> Hello Szabolcs, list,
> 
> I installed a Gentoo musl-1.1.15 x86_64 chroot on my computer. Then I
> ran ./configure in apr-1.5.2 in the musl chroot and also outside the
> chroot in a glibc-2.22 environment.
> 
> The outcome was the same except for apr_cv_mutex_robust_shared:
> 
> ac_cv_func_setpgrp_void         musl yes glibc yes
> ac_cv_file__dev_zero            musl yes glibc yes
> apr_cv_tcp_nodelay_with_cork    musl yes glibc yes
> apr_cv_mutex_recursive          musl yes glibc yes
> ac_cv_func_pthread_rwlock_init  musl yes glibc yes
> apr_cv_type_rwlock_t=yes        musl yes glibc yes
> apr_cv_process_shared_works     musl yes glibc yes
> apr_cv_mutex_robust_shared      musl no  glibc yes
> 
> I've posted the corresponding part from config.log below. It fails
> because musl doesn't define PTHREAD_MUTEX_ROBUST_NP (glibc does). And
> apr uses PTHREAD_MUTEX_ROBUST_NP. It means that I should set
> apr_cv_mutex_robust_shared=no when cross-compiling this apr, I suppose
> :)

the standard name is PTHREAD_MUTEX_ROBUST since posix2008,
so this is an apr bug.

> configure:25459: checking for robust cross-process mutex support
> configure:25500: gcc -o conftest -g -O2 -DLINUX -D_REENTRANT -D_GNU_SOURCE  conftest.c -lpthread >&5
> conftest.c: In function 'main':
> conftest.c:197:47: error: 'PTHREAD_MUTEX_ROBUST_NP' undeclared (first use in this function)
>      if (pthread_mutexattr_setrobust_np(&attr, PTHREAD_MUTEX_ROBUST_NP))
>                                                ^

i think they should use the standard name and provide
their own definition on legacy systems

#ifndef PTHREAD_MUTEX_ROBUST
#define PTHREAD_MUTEX_ROBUST PTHREAD_MUTEX_ROBUST_NP
#endif