Hi all,
in my app, some threads that cannot be detached a-priori : sometimes,
they
have to be joinable, but sometimes they can be detached (no other
thread
will wait for them).
At the same time, I needed to be sure that storage of all the thread
are
reclaimed when they terminate.
I set up a solution on Linux that ran properly.
On linux, I always detached the thread that may be joined JUST BEFORE
it
exists.
In case this thread was not awaited (no pending call to pthread_join()
by
another thread), its storage was reclaimed when terminating.
In case this thread was already awaited (joined) by another thread, the
pthread_join in the other thread resulted in a error EINVAL indicating
that the thread was detached. However, the storage was still reclaimed
when terminating, and the pthread_join exited when the joined thread
terminates (or just before). In a few words, it was 'OK'.
Here is an example of the code :
// THREAD 1 routine
// (thread 1 pthread_t is thread1_id)
void thread1_routine(void *data) {
// do some work
// wait for thread 2
// As an example, thread2 is here always joined.
// However, in my app, it is joined only in some cases
int res = pthread_join(thread2_id, NULL);
// in case the thread2 was not already terminated, EINVAL is
returned...
// in case the thread2 wa already terminated, ESRCH is returned...
if( res != 0) {
switch(res) {
case ESRCH :
printf("pthread_join error the thread is not valid\n");
break;
case EINVAL :
printf("the thread is already detached\n");
break;
case EDEADLK :
printf("called by the calling thread\n");
break;
default :
couterr <<"unknown"<<endl;
break;
}
}
}
// THREAD 2 routine
// (thread 2 pthread_t is thread2_id)
void thread2_routine(void *data) {
// do some work
// before terminating, detach the thread to be sure its storage is
reclaimed
int res = pthread_detach(thread2_id, NULL);
if( res != 0) {
switch(res) {
case ESRCH :
printf("the thread is not valid \n");
break;
case EINVAL :
printf("the thread is already detached\n);
break;
}
pthread_exit(NULL);
}
As far as I chercked, a code like this one does not run on mac os X.
The call to pthread_join results in :
mach_port_mod_refs(reply_port) failed: (os/kern) invalid name
mach_port_deallocate(kernel_thread) failed: (os/kern) invalid name
and sometimes in :
mach_port_deallocate(kernel_thread) failed: (os/kern) invalid name
*** malloc[1243]: Deallocation of a pointer not malloced: 0x580bc00;
This
could be a double free(), or free() called with the middle of an
allocated
block; Try setting environment variable MallocHelp to see tools to help
debug
(then, the program aborts).
Indeed, it seems that we cannot call pthread_detach on a thread while
this
thread is already by another thread awaited within a pthread_join.
Is that true ?
If it is, well... It is not documented in the man pages...
Does it correspond with the POSIX standard, or should I register it as
a
bug ?
Thx,
Nicolas
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