diff options
| -rw-r--r-- | src/env/__init_tls.c | 4 | ||||
| -rw-r--r-- | src/internal/pthread_impl.h | 12 | ||||
| -rw-r--r-- | src/thread/pthread_create.c | 21 | ||||
| -rw-r--r-- | src/thread/pthread_detach.c | 7 | ||||
| -rw-r--r-- | src/thread/pthread_getattr_np.c | 2 | ||||
| -rw-r--r-- | src/thread/pthread_join.c | 11 |
6 files changed, 33 insertions, 24 deletions
diff --git a/src/env/__init_tls.c b/src/env/__init_tls.c index 80044960..1c5d98a0 100644 --- a/src/env/__init_tls.c +++ b/src/env/__init_tls.c @@ -15,8 +15,8 @@ int __init_tp(void *p) int r = __set_thread_area(TP_ADJ(p)); if (r < 0) return -1; if (!r) libc.can_do_threads = 1; - td->join_futex = -1; - td->tid = __syscall(SYS_set_tid_address, &td->join_futex); + td->detach_state = DT_JOINABLE; + td->tid = __syscall(SYS_set_tid_address, &td->detach_state); td->locale = &libc.global_locale; td->robust_list.head = &td->robust_list.head; return 0; diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h index 3b4ad94d..0a65fa37 100644 --- a/src/internal/pthread_impl.h +++ b/src/internal/pthread_impl.h @@ -24,7 +24,7 @@ struct pthread { /* Part 2 -- implementation details, non-ABI. */ int tsd_used, errno_val; volatile int cancel, canceldisable, cancelasync; - int detached; + volatile int detach_state; unsigned char *map_base; size_t map_size; void *stack; @@ -42,9 +42,7 @@ struct pthread { int unblock_cancel; volatile int timer_id; locale_t locale; - volatile int join_futex; volatile int killlock[1]; - volatile int exitlock[1]; volatile int startlock[2]; unsigned long sigmask[_NSIG/8/sizeof(long)]; char *dlerror_buf; @@ -58,6 +56,14 @@ struct pthread { void **dtv_copy; }; +enum { + DT_EXITED = 0, + DT_EXITING, + DT_JOINABLE, + DT_DETACHED, + DT_DYNAMIC, +}; + struct __timer { int timerid; pthread_t thread; diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c index a86b5e1b..e07d29e3 100644 --- a/src/thread/pthread_create.c +++ b/src/thread/pthread_create.c @@ -37,8 +37,6 @@ _Noreturn void __pthread_exit(void *result) __pthread_tsd_run_dtors(); - LOCK(self->exitlock); - /* Access to target the exiting thread with syscalls that use * its kernel tid is controlled by killlock. For detached threads, * any use past this point would have undefined behavior, but for @@ -85,15 +83,19 @@ _Noreturn void __pthread_exit(void *result) __do_orphaned_stdio_locks(); __dl_thread_cleanup(); - if (self->detached && self->map_base) { + /* This atomic potentially competes with a concurrent pthread_detach + * call; the loser is responsible for freeing thread resources. */ + int state = a_cas(&self->detach_state, DT_JOINABLE, DT_EXITING); + + if (state>=DT_DETACHED && self->map_base) { /* Detached threads must avoid the kernel clear_child_tid * feature, since the virtual address will have been * unmapped and possibly already reused by a new mapping * at the time the kernel would perform the write. In * the case of threads that started out detached, the * initial clone flags are correct, but if the thread was - * detached later (== 2), we need to clear it here. */ - if (self->detached == 2) __syscall(SYS_set_tid_address, 0); + * detached later, we need to clear it here. */ + if (state == DT_DYNAMIC) __syscall(SYS_set_tid_address, 0); /* Robust list will no longer be valid, and was already * processed above, so unregister it with the kernel. */ @@ -141,7 +143,7 @@ static int start(void *p) if (self->startlock[0]) { __wait(self->startlock, 0, 1, 1); if (self->startlock[0] == 2) { - self->detached = 2; + self->detach_state = DT_DYNAMIC; pthread_exit(0); } __restore_sigs(self->sigmask); @@ -274,8 +276,10 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att new->tsd = (void *)tsd; new->locale = &libc.global_locale; if (attr._a_detach) { - new->detached = 1; + new->detach_state = DT_DETACHED; flags -= CLONE_CHILD_CLEARTID; + } else { + new->detach_state = DT_JOINABLE; } if (attr._a_sched) { do_sched = new->startlock[0] = 1; @@ -284,10 +288,9 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att new->robust_list.head = &new->robust_list.head; new->unblock_cancel = self->cancel; new->CANARY = self->CANARY; - new->join_futex = -1; a_inc(&libc.threads_minus_1); - ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->join_futex); + ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->detach_state); __release_ptc(); diff --git a/src/thread/pthread_detach.c b/src/thread/pthread_detach.c index 692bbaf9..9cee7a89 100644 --- a/src/thread/pthread_detach.c +++ b/src/thread/pthread_detach.c @@ -5,11 +5,10 @@ int __pthread_join(pthread_t, void **); static int __pthread_detach(pthread_t t) { - /* Cannot detach a thread that's already exiting */ - if (a_cas(t->exitlock, 0, INT_MIN + 1)) + /* If the cas fails, detach state is either already-detached + * or exiting/exited, and pthread_join will trap or cleanup. */ + if (a_cas(&t->detach_state, DT_JOINABLE, DT_DYNAMIC) != DT_JOINABLE) return __pthread_join(t, 0); - t->detached = 2; - UNLOCK(t->exitlock); return 0; } diff --git a/src/thread/pthread_getattr_np.c b/src/thread/pthread_getattr_np.c index 29a209bd..2881831f 100644 --- a/src/thread/pthread_getattr_np.c +++ b/src/thread/pthread_getattr_np.c @@ -6,7 +6,7 @@ int pthread_getattr_np(pthread_t t, pthread_attr_t *a) { *a = (pthread_attr_t){0}; - a->_a_detach = !!t->detached; + a->_a_detach = t->detach_state>=DT_DETACHED; a->_a_guardsize = t->guard_size; if (t->stack) { a->_a_stackaddr = (uintptr_t)t->stack; diff --git a/src/thread/pthread_join.c b/src/thread/pthread_join.c index 67eaf9d8..18264da6 100644 --- a/src/thread/pthread_join.c +++ b/src/thread/pthread_join.c @@ -7,13 +7,14 @@ int __pthread_setcancelstate(int, int *); int __pthread_timedjoin_np(pthread_t t, void **res, const struct timespec *at) { - int tmp, cs, r = 0; + int state, cs, r = 0; __pthread_testcancel(); __pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs); if (cs == PTHREAD_CANCEL_ENABLE) __pthread_setcancelstate(cs, 0); - if (t->detached) a_crash(); - while ((tmp = t->join_futex) && r != ETIMEDOUT && r != EINVAL) - r = __timedwait_cp(&t->join_futex, tmp, CLOCK_REALTIME, at, 0); + while ((state = t->detach_state) && r != ETIMEDOUT && r != EINVAL) { + if (state >= DT_DETACHED) a_crash(); + r = __timedwait_cp(&t->detach_state, state, CLOCK_REALTIME, at, 0); + } __pthread_setcancelstate(cs, 0); if (r == ETIMEDOUT || r == EINVAL) return r; a_barrier(); @@ -29,7 +30,7 @@ int __pthread_join(pthread_t t, void **res) int __pthread_tryjoin_np(pthread_t t, void **res) { - return t->join_futex ? EBUSY : __pthread_join(t, res); + return t->detach_state==DT_JOINABLE ? EBUSY : __pthread_join(t, res); } weak_alias(__pthread_tryjoin_np, pthread_tryjoin_np); |