Date: Mon, 21 Nov 2016 15:16:16 +0100 From: Volker Lendecke <Volker.Lendecke@SerNet.DE> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org Subject: Re: process shared mutexes? Message-ID: <20161121141616.GB30947@sernet.de> In-Reply-To: <20161121135036.GY54029@kib.kiev.ua> References: <20161121133528.GA30947@sernet.de> <20161121135036.GY54029@kib.kiev.ua>
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On Mon, Nov 21, 2016 at 03:50:36PM +0200, Konstantin Belousov wrote:
> On Mon, Nov 21, 2016 at 02:35:28PM +0100, Volker Lendecke wrote:
> > Hello!
> >
> > For Samba's tdb I'm trying to get process shared robust mutexes to
> > work. However, tdb has a usage pattern that seems to confuse FreeBSD
> > 11 (32-bit x86 if that matters).
> >
> > The attached program fails in the final pthread_mutex_lock call. If I
> > comment out the call to
> >
> > ptr = mmap(NULL, 0xb0, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x1000);
> >
> > it works.
> >
> > FWIW, tdb uses robust shared mutexes on Linux successfully for a while
> > now. I haven't tried Solaris yet, the only other platform I know about
> > that has them.
> >
> > What am I doing wrong?
> >
> > Thanks,
> >
>
> There is no attached program, please mail it either inline or put it
> somewhere on web.
Hmm. Inline now.
Volker
#include <stdio.h>
#include <pthread.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <string.h>
int main(int argc, const char *argv[])
{
int fd, ret;
void *ptr;
pthread_mutex_t *m;
pthread_mutexattr_t attr;
if (argc != 2) {
fprintf(stderr, "usage: %s <filename>\n", argv[0]);
return 1;
}
fd = open(argv[1], O_RDWR|O_CREAT, 0644);
if (fd == -1) {
perror("open failed");
return 1;
}
ret = ftruncate(fd, 0x1000+0xb0);
if (ret == -1) {
perror("ftruncate failed");
return 1;
}
m = mmap(NULL, 0x1000, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
if (m == MAP_FAILED) {
perror("mmap failed");
return 1;
}
ret = pthread_mutexattr_init(&attr);
if (ret != 0) {
fprintf(stderr, "pthread_mutexattr_init failed: %s\n",
strerror(ret));
return 1;
}
ret = pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
if (ret != 0) {
fprintf(stderr, "pthread_mutexattr_setpshared failed: %s\n",
strerror(ret));
return 1;
}
ret = pthread_mutex_init(m, &attr);
if (ret != 0) {
fprintf(stderr, "pthread_mutex_init failed: %s\n",
strerror(ret));
return 1;
}
ret = munmap(m, 0x1000);
if (ret == -1) {
perror("munmap failed");
return 1;
}
#if 1
ptr = mmap(NULL, 0xb0, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x1000);
if (ptr == MAP_FAILED) {
perror("mmap failed");
return 1;
}
#endif
m = mmap(NULL, 0x1000, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
if (m == MAP_FAILED) {
perror("mmap failed");
return 1;
}
ret = pthread_mutex_lock(m);
if (ret != 0) {
fprintf(stderr, "pthread_mutex_lock failed: %s\n",
strerror(ret));
return 1;
}
ret = pthread_mutex_unlock(m);
if (ret != 0) {
fprintf(stderr, "pthread_mutex_lock failed: %s\n",
strerror(ret));
return 1;
}
return 0;
}
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