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Support process shared pthread_rwlock

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Cosmo now has a non-nsync implementation of POSIX read-write locks. It's
possible to call pthread_rwlockattr_setpshared in PTHREAD_PROCESS_SHARED
mode. Furthermore, if cosmo is built with PTHREAD_USE_NSYNC set to zero,
then Cosmo shouldn't use nsync at all. That's helpful if you want to not
link any Apache 2.0 licensed code.
This commit is contained in:
Justine Tunney 2024-12-13 02:50:19 -08:00
parent c22b413ac4
commit 2d43d400c6
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GPG key ID: BE714B4575D6E328
11 changed files with 179 additions and 35 deletions
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16
libc/thread/pthread_rwlock_destroy.c
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@ -16,16 +16,30 @@
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/errno.h"
#include "libc/intrin/atomic.h"
#include "libc/str/str.h"
#include "libc/thread/thread.h"
#include "third_party/nsync/mu.h"
/**
* Destroys read-write lock.
*
* @return 0 on success, or error number on failure
* @raise EINVAL if any threads still hold the lock
* @raise EBUSY if any threads still hold the lock
*/
errno_t pthread_rwlock_destroy(pthread_rwlock_t *rwlock) {
// check if lock is held
if (!rwlock->_pshared) {
nsync_mu *mu = (nsync_mu *)rwlock->_nsync;
if (atomic_load_explicit(&mu->word, memory_order_relaxed))
return EBUSY;
} else {
if (atomic_load_explicit(&rwlock->_word, memory_order_relaxed))
return EBUSY;
}
memset(rwlock, -1, sizeof(*rwlock));
return 0;
}