diff options
| -rw-r--r-- | lib/libthr/thread/thr_mutex.c | 55 | ||||
| -rw-r--r-- | lib/libthr/thread/thr_private.h | 8 |
2 files changed, 61 insertions, 2 deletions
diff --git a/lib/libthr/thread/thr_mutex.c b/lib/libthr/thread/thr_mutex.c index 3342c9f..865e4cf 100644 --- a/lib/libthr/thread/thr_mutex.c +++ b/lib/libthr/thread/thr_mutex.c @@ -38,6 +38,7 @@ * $FreeBSD$ */ +#include <stdbool.h> #include "namespace.h" #include <stdlib.h> #include <errno.h> @@ -264,6 +265,51 @@ set_inherited_priority(struct pthread *curthread, struct pthread_mutex *m) m->m_lock.m_ceilings[1] = -1; } +static void +shared_mutex_init(struct pthread_mutex *pmtx, const struct + pthread_mutex_attr *mutex_attr) +{ + static const struct pthread_mutex_attr foobar_mutex_attr = { + .m_type = PTHREAD_MUTEX_DEFAULT, + .m_protocol = PTHREAD_PRIO_NONE, + .m_ceiling = 0, + .m_pshared = PTHREAD_PROCESS_SHARED + }; + bool done; + + /* + * Hack to allow multiple pthread_mutex_init() calls on the + * same process-shared mutex. We rely on kernel allocating + * zeroed offpage for the mutex, i.e. the + * PMUTEX_INITSTAGE_ALLOC value must be zero. + */ + for (done = false; !done;) { + switch (pmtx->m_ps) { + case PMUTEX_INITSTAGE_DONE: + atomic_thread_fence_acq(); + done = true; + break; + case PMUTEX_INITSTAGE_ALLOC: + if (atomic_cmpset_int(&pmtx->m_ps, + PMUTEX_INITSTAGE_ALLOC, PMUTEX_INITSTAGE_BUSY)) { + if (mutex_attr == NULL) + mutex_attr = &foobar_mutex_attr; + mutex_init_body(pmtx, mutex_attr); + atomic_store_rel_int(&pmtx->m_ps, + PMUTEX_INITSTAGE_DONE); + done = true; + } + break; + case PMUTEX_INITSTAGE_BUSY: + _pthread_yield(); + break; + default: + PANIC("corrupted offpage"); + break; + } + } +} + int __pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutex_attr) @@ -285,7 +331,7 @@ __pthread_mutex_init(pthread_mutex_t *mutex, if (pmtx == NULL) return (EFAULT); *mutex = THR_PSHARED_PTR; - mutex_init_body(pmtx, *mutex_attr); + shared_mutex_init(pmtx, *mutex_attr); return (0); } @@ -426,6 +472,7 @@ check_and_init_mutex(pthread_mutex_t *mutex, struct pthread_mutex **m) *m = __thr_pshared_offpage(mutex, 0); if (*m == NULL) ret = EINVAL; + shared_mutex_init(*m, NULL); } else if (__predict_false(*m <= THR_MUTEX_DESTROYED)) { if (*m == THR_MUTEX_DESTROYED) { ret = EINVAL; @@ -588,6 +635,7 @@ _pthread_mutex_unlock(pthread_mutex_t *mutex) mp = __thr_pshared_offpage(mutex, 0); if (mp == NULL) return (EINVAL); + shared_mutex_init(mp, NULL); } else { mp = *mutex; } @@ -815,6 +863,7 @@ _pthread_mutex_getprioceiling(pthread_mutex_t *mutex, m = __thr_pshared_offpage(mutex, 0); if (m == NULL) return (EINVAL); + shared_mutex_init(m, NULL); } else { m = *mutex; if (m <= THR_MUTEX_DESTROYED) @@ -839,6 +888,7 @@ _pthread_mutex_setprioceiling(pthread_mutex_t *mutex, m = __thr_pshared_offpage(mutex, 0); if (m == NULL) return (EINVAL); + shared_mutex_init(m, NULL); } else { m = *mutex; if (m <= THR_MUTEX_DESTROYED) @@ -942,12 +992,13 @@ __pthread_mutex_setyieldloops_np(pthread_mutex_t *mutex, int count) int _pthread_mutex_isowned_np(pthread_mutex_t *mutex) { - struct pthread_mutex *m; + struct pthread_mutex *m; if (*mutex == THR_PSHARED_PTR) { m = __thr_pshared_offpage(mutex, 0); if (m == NULL) return (0); + shared_mutex_init(m, NULL); } else { m = *mutex; if (m <= THR_MUTEX_DESTROYED) diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h index 7ee1fbf..0db2dad 100644 --- a/lib/libthr/thread/thr_private.h +++ b/lib/libthr/thread/thr_private.h @@ -146,6 +146,13 @@ TAILQ_HEAD(mutex_queue, pthread_mutex); #define MAX_DEFER_WAITERS 50 +/* + * Values for pthread_mutex m_ps indicator. + */ +#define PMUTEX_INITSTAGE_ALLOC 0 +#define PMUTEX_INITSTAGE_BUSY 1 +#define PMUTEX_INITSTAGE_DONE 2 + struct pthread_mutex { /* * Lock for accesses to this structure. @@ -156,6 +163,7 @@ struct pthread_mutex { int m_count; int m_spinloops; int m_yieldloops; + int m_ps; /* pshared init stage */ /* * Link for all mutexes a thread currently owns, of the same * prio type. |
