weak_alias(dummy_0, __do_orphaned_stdio_locks);
weak_alias(dummy_0, __dl_thread_cleanup);
+static void *dummy_1(void *p)
+{
+ return 0;
+}
+weak_alias(dummy_1, __start_sched);
+
_Noreturn void __pthread_exit(void *result)
{
pthread_t self = __pthread_self();
__pthread_tsd_run_dtors();
- __lock(self->exitlock);
-
- /* Mark this thread dead before decrementing count */
- __lock(self->killlock);
- self->dead = 1;
+ /* 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
+ * joinable threads it's a valid usage that must be handled. */
+ LOCK(self->killlock);
/* Block all signals before decrementing the live thread count.
* This is important to ensure that dynamically allocated TLS
* reasons as well. */
__block_all_sigs(&set);
- /* Wait to unlock the kill lock, which governs functions like
- * pthread_kill which target a thread id, until signals have
- * been blocked. This precludes observation of the thread id
- * as a live thread (with application code running in it) after
- * the thread was reported dead by ESRCH being returned. */
- __unlock(self->killlock);
-
/* It's impossible to determine whether this is "the last thread"
* until performing the atomic decrement, since multiple threads
* could exit at the same time. For the last thread, revert the
- * decrement and unblock signals to give the atexit handlers and
- * stdio cleanup code a consistent state. */
+ * decrement, restore the tid, and unblock signals to give the
+ * atexit handlers and stdio cleanup code a consistent state. */
if (a_fetch_add(&libc.threads_minus_1, -1)==0) {
libc.threads_minus_1 = 0;
+ UNLOCK(self->killlock);
__restore_sigs(&set);
exit(0);
}
__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. */
__unmapself(self->map_base, self->map_size);
}
+ /* After the kernel thread exits, its tid may be reused. Clear it
+ * to prevent inadvertent use and inform functions that would use
+ * it that it's no longer available. */
+ self->tid = 0;
+ UNLOCK(self->killlock);
+
for (;;) __syscall(SYS_exit, 0);
}
static int start(void *p)
{
pthread_t self = p;
- if (self->startlock[0]) {
- __wait(self->startlock, 0, 1, 1);
- if (self->startlock[0]) {
- self->detached = 2;
- pthread_exit(0);
- }
- __restore_sigs(self->sigmask);
- }
if (self->unblock_cancel)
__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
SIGPT_SET, 0, _NSIG/8);
weak_alias(dummy_tsd, __pthread_tsd_main);
volatile int __block_new_threads = 0;
-size_t __default_stacksize = DEFAULT_STACK_SIZE;
-size_t __default_guardsize = DEFAULT_GUARD_SIZE;
+extern size_t __default_stacksize;
+extern size_t __default_guardsize;
static FILE *volatile dummy_file = 0;
weak_alias(dummy_file, __stdin_used);
| CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
int do_sched = 0;
pthread_attr_t attr = { 0 };
+ struct start_sched_args ssa;
if (!libc.can_do_threads) return ENOSYS;
self = __pthread_self();
memset(stack, 0, need);
} else {
size = ROUND(need);
- guard = 0;
}
+ guard = 0;
} else {
guard = ROUND(attr._a_guardsize);
size = guard + ROUND(attr._a_stacksize
new->map_size = size;
new->stack = stack;
new->stack_size = stack - stack_limit;
+ new->guard_size = guard;
new->start = entry;
new->start_arg = arg;
new->self = new;
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;
- __block_app_sigs(new->sigmask);
+ do_sched = 1;
+ ssa.futex = -1;
+ ssa.start_fn = new->start;
+ ssa.start_arg = new->start_arg;
+ ssa.attr = &attr;
+ new->start = __start_sched;
+ new->start_arg = &ssa;
+ __block_app_sigs(&ssa.mask);
}
new->robust_list.head = &new->robust_list.head;
new->unblock_cancel = self->cancel;
new->CANARY = self->CANARY;
a_inc(&libc.threads_minus_1);
- ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->tid);
+ ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->detach_state);
__release_ptc();
if (do_sched) {
- __restore_sigs(new->sigmask);
+ __restore_sigs(&ssa.mask);
}
if (ret < 0) {
}
if (do_sched) {
- ret = __syscall(SYS_sched_setscheduler, new->tid,
- attr._a_policy, &attr._a_prio);
- a_store(new->startlock, ret<0 ? 2 : 0);
- __wake(new->startlock, 1, 1);
- if (ret < 0) return -ret;
+ __futexwait(&ssa.futex, -1, 1);
+ if (ret) return ret;
}
*res = new;
projects / musl / blobdiff