--- Begin Message ---
- To: Debian Bug Tracking System <submit@bugs.debian.org>
- Subject: libc-bin: robust mutex deadlocks instead of returning EOWNERDEAD
- From: Andrey Semashev <andysem@mail.ru>
- Date: Thu, 07 Nov 2013 18:24:46 +0400
- Message-id: <20131107142446.3491.52742.reportbug@bugatti.mcdlabs.net>
Package: libc-bin
Version: 2.13-38
Severity: normal
Dear Maintainer,
This bug has been reported as: http://sourceware.org/bugzilla/show_bug.cgi?id=13002 and http://bugzilla.redhat.com/show_bug.cgi?id=628608
If a parent process and child process share a robust mutex and the child exits
while holding the mutex lock, when the parent tries to acquire the lock it will
hang instead of being notified of the state by EOWNERDEAD.
Here's a testcase which exits successfully on Solaris but deadlocks with NPTL
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <pthread.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
void initialize(pthread_mutex_t* mtx)
{
pthread_mutexattr_t mtxa;
if(pthread_mutexattr_init(&mtxa))
abort();
if(pthread_mutexattr_setpshared(&mtxa, PTHREAD_PROCESS_SHARED))
abort();
if(pthread_mutexattr_setrobust_np(&mtxa, PTHREAD_MUTEX_ROBUST_NP))
abort();
if(pthread_mutex_init(mtx, &mtxa))
abort();
pthread_mutexattr_destroy(&mtxa);
}
void set_consistent(pthread_mutex_t* mtx)
{
if(pthread_mutex_consistent_np(mtx))
abort();
}
void lock(pthread_mutex_t* mtx)
{
int err;
if((err = pthread_mutex_lock(mtx))) {
if(EOWNERDEAD == err) { // handle abandoned mutex
if(pthread_mutex_consistent_np(mtx))
abort();
}
else
abort();
}
}
void unlock(pthread_mutex_t* mtx)
{
if(pthread_mutex_unlock(mtx))
abort();
}
pid_t spawn(int(*fn)())
{
// fork a child process
pid_t pid = fork();
switch(pid) {
case 0:
exit(fn());
case -1:
abort();
default:
return pid;
}
}
char const shared_file[] = "shared_file";
void* open_shared_file()
{
int fd = open(shared_file, O_CREAT | O_RDWR, (mode_t)0666);
if(fd < 0)
abort();
struct stat st;
if(fstat(fd, &st))
abort();
int new_file = !st.st_size;
if (new_file)
if(ftruncate(fd, sizeof(pthread_mutex_t)))
abort();
void* mem = mmap(NULL, sizeof(pthread_mutex_t), PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
close(fd);
if(MAP_FAILED == mem)
abort();
if (new_file)
initialize((pthread_mutex_t*)mem);
return mem;
}
int process_1()
{
unsigned pid = getpid();
printf("%u: process 1\n", pid);
pthread_mutex_t* m = (pthread_mutex_t*)open_shared_file();
printf("%u: locking mutex...\n", pid);
lock(m);
printf("%u: exiting\n", pid);
return 0;
}
int process_2()
{
unsigned pid = getpid();
printf("%u: process 2\n", pid);
pthread_mutex_t* m = (pthread_mutex_t*)open_shared_file();
printf("%u: locking mutex...\n", pid);
lock(m);
printf("%u: mutex locked\n", pid);
unlock(m);
return 0;
}
int main(int ac, char** av)
{
// fork process_1 and wait till it terminates
pid_t child;
unlink(shared_file);
int child_status;
child = spawn(process_1);
if(-1 == waitpid(child, &child_status, 0))
abort();
// now do process_2
return process_2();
}
-- System Information:
Debian Release: 7.2
APT prefers stable
APT policy: (400, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 3.2.0-4-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
-- no debconf information
--- End Message ---
--- Begin Message ---
- To: Andrey Semashev <andysem@mail.ru>
- Cc: 708750-done@bugs.debian.org
- Subject: Re: libc-bin: robust mutex deadlocks instead of returning EOWNERDEAD
- From: Aurelien Jarno <aurelien@aurel32.net>
- Date: Sat, 22 Feb 2014 23:34:17 +0100
- Message-id: <20140222223416.GA15928@volta.rr44.fr>
- In-reply-to: <20130518110143.10614.74071.reportbug@vaz.mcdlabs.net>
- References: <20130518110143.10614.74071.reportbug@vaz.mcdlabs.net>
Version: 2.17-1
On Sat, May 18, 2013 at 03:01:43PM +0400, Andrey Semashev wrote:
> Package: libc-bin
> Version: 2.11.3-4
> Severity: normal
>
>
> This bug has been reported as: http://sourceware.org/bugzilla/show_bug.cgi?id=13002 and http://bugzilla.redhat.com/show_bug.cgi?id=628608
> At least, Debian Squeeze and Wheezy are affected. Kubuntu 13.04 seem to be not affected by this.
>
> If a parent process and child process share a robust mutex and the child exits
> while holding the mutex lock, when the parent tries to acquire the lock it will
> hang instead of being notified of the state by EOWNERDEAD.
This bug has been fixed in libc6 version 2.17-1. Marking the bug as
fixed in this version.
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@aurel32.net http://www.aurel32.net
--- End Message ---