mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-07-12 05:59:10 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

Support process shared pthread_rwlock

Browse source 
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
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
11 changed files with 179 additions and 35 deletions
Download patch file Download diff file Expand all files Collapse all files

36
libc/thread/pthread_rwlock_unlock.c
View file

@ -16,6 +16,8 @@
│ 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/thread/thread.h"
#include "third_party/nsync/mu.h"
@ -26,11 +28,33 @@
* @raise EINVAL if lock is in a bad state
*/
errno_t pthread_rwlock_unlock(pthread_rwlock_t *rwlock) {
if (rwlock->_iswrite) {
rwlock->_iswrite = 0;
nsync_mu_unlock((nsync_mu *)rwlock);
} else {
nsync_mu_runlock((nsync_mu *)rwlock);
#if PTHREAD_USE_NSYNC
// use nsync if possible
if (!rwlock->_pshared) {
if (rwlock->_iswrite) {
rwlock->_iswrite = 0;
nsync_mu_unlock((nsync_mu *)rwlock->_nsync);
} else {
nsync_mu_runlock((nsync_mu *)rwlock->_nsync);
}
return 0;
}
#endif
// naive implementation
uint32_t word = atomic_load_explicit(&rwlock->_word, memory_order_relaxed);
for (;;) {
if (word & 1) {
atomic_store_explicit(&rwlock->_word, 0, memory_order_release);
return 0;
} else if (word) {
if (atomic_compare_exchange_weak_explicit(&rwlock->_word, &word, word - 2,
memory_order_release,
memory_order_relaxed))
return 0;
} else {
return EPERM;
}
}
return 0;
}