Re: [PATCH] make rwlocks SHAREABLE + cleanups

Am Freitag den, 30. August 2002, um 01:47, schrieb Saurabh Desai:
>
> I have a question regarding the following changes in 
> pth_mutex_release():
>
> +    if (!mutex->mx_shared.pshared && mutex->mx_owner != current) return
> EPERM;
>
> Why this check is not needed for the pshared case? The mx_owner is 
> always
> set to current in pth_mutex_acquire() for both normal and pshared 
> mutexes.
>

I thought the pointers wouldn't have to be the same in different 
processes
and address spaces.

Process A aquires the lock - mutex->mx_owner=0xADDA
Process B tries to release it (which is wrong) - ok, mx_owner is still 
NULL in
_this_ address space

I got that wrong.

For EDEADLK we have to test if the lock is already held by the caller - 
but
only if the mutex is not PTHREAD_MUTEX_RECURSIVE.

Does the check belongs here?
pth_sync.s:239
wait:
     /* already locked by caller? */
     if (mutex->mx_count >= 1 && mutex->mx_owner == current &&
     mutex->mx_owner_pid==descr->pid &&
     mutex->mx_type == PTH_MUTEX_RECURSIVE_NP) {
         /* recursive lock */
         mutex->mx_count++;
         _pth_release_lock(&(mutex->mx_lock), descr->tid);
         return 0;
     }

     /* should we just tryonly?                    ibm*/
     if (tryonly) {                              /*ibm*/
         _pth_release_lock(&(mutex->mx_lock), descr->tid);
         return EBUSY;                           /*ibm*/
!    } else
!	return EDEADLK;


> Also,  if (!(mutex->mx_state & PTH_MUTEX_INITIALIZED)) return EINVAL;
> is not needed, because the caller always check for valid mx_mutex.
>

The caller checks against mx_init.  But perhaps I'm still too dazed and 
get this
also wrong.. ;-)
pth_mutex_init sets mx_state to PTH_MUTEX_INITIALIZED, but the flag is
also used to check if it's locked or not. I don't know if these tests 
are obsolete.

Keep up the good work.