weak_alias(dummy_0, __do_orphaned_stdio_locks);
weak_alias(dummy_0, __dl_thread_cleanup);
-static void *dummy_1(void *p)
+void __tl_lock(void)
{
- return 0;
+ if (!a_cas(&__thread_list_lock, 0, 1)) return;
+ do {
+ a_cas(&__thread_list_lock, 1, 2);
+ __futexwait(&__thread_list_lock, 2, 0);
+ } while (a_cas(&__thread_list_lock, 0, 2));
+}
+
+void __tl_unlock(void)
+{
+ if (a_swap(&__thread_list_lock, 0)==2)
+ __wake(&__thread_list_lock, 1, 0);
+}
+
+void __tl_sync(pthread_t td)
+{
+ a_barrier();
+ if (!__thread_list_lock) return;
+ a_cas(&__thread_list_lock, 1, 2);
+ __wait(&__thread_list_lock, 0, 2, 0);
+ __wake(&__thread_list_lock, 1, 0);
}
-weak_alias(dummy_1, __start_sched);
_Noreturn void __pthread_exit(void *result)
{
* 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
- * is not under-allocated/over-committed, and possibly for other
- * reasons as well. */
- __block_all_sigs(&set);
-
- /* 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, 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);
+ /* The thread list lock must be AS-safe, and thus requires
+ * application signals to be blocked before it can be taken. */
+ __block_app_sigs(&set);
+ __tl_lock();
+
+ /* If this is the only thread in the list, don't proceed with
+ * termination of the thread, but restore the previous lock and
+ * signal state to prepare for exit to call atexit handlers. */
+ if (self->next == self) {
+ __tl_unlock();
__restore_sigs(&set);
+ UNLOCK(self->killlock);
exit(0);
}
+ /* At this point we are committed to thread termination. Unlink
+ * the thread from the list. This change will not be visible
+ * until the lock is released, which only happens after SYS_exit
+ * has been called, via the exit futex address pointing at the lock. */
+ libc.threads_minus_1--;
+ self->next->prev = self->prev;
+ self->prev->next = self->next;
+ self->prev = self->next = self;
+
/* Process robust list in userspace to handle non-pshared mutexes
* and the detached thread case where the robust list head will
* be invalid when the kernel would process it. */
* 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, we need to clear it here. */
- if (state == DT_DYNAMIC) __syscall(SYS_set_tid_address, 0);
+ if (state==DT_DETACHED && self->map_base) {
+ /* Detached threads must block even implementation-internal
+ * signals, since they will not have a stack in their last
+ * moments of existence. */
+ __block_all_sigs(&set);
/* 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);
}
+ /* Wake any joiner. */
+ __wake(&self->detach_state, 1, 1);
+
/* 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. */
__pthread_self()->cancelbuf = cb->__next;
}
+struct start_args {
+ void *(*start_func)(void *);
+ void *start_arg;
+ pthread_attr_t *attr;
+ volatile int *perr;
+ unsigned long sig_mask[_NSIG/8/sizeof(long)];
+};
+
static int start(void *p)
{
- pthread_t self = p;
- if (self->unblock_cancel)
- __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
- SIGPT_SET, 0, _NSIG/8);
- __pthread_exit(self->start(self->start_arg));
+ struct start_args *args = p;
+ if (args->attr) {
+ pthread_t self = __pthread_self();
+ int ret = -__syscall(SYS_sched_setscheduler, self->tid,
+ args->attr->_a_policy, &args->attr->_a_prio);
+ if (a_swap(args->perr, ret)==-2)
+ __wake(args->perr, 1, 1);
+ if (ret) {
+ self->detach_state = DT_DETACHED;
+ __pthread_exit(0);
+ }
+ }
+ __syscall(SYS_rt_sigprocmask, SIG_SETMASK, &args->sig_mask, 0, _NSIG/8);
+ __pthread_exit(args->start_func(args->start_arg));
return 0;
}
static int start_c11(void *p)
{
- pthread_t self = p;
- int (*start)(void*) = (int(*)(void*)) self->start;
- __pthread_exit((void *)(uintptr_t)start(self->start_arg));
+ struct start_args *args = p;
+ int (*start)(void*) = (int(*)(void*)) args->start_func;
+ __pthread_exit((void *)(uintptr_t)start(args->start_arg));
return 0;
}
weak_alias(dummy_tsd, __pthread_tsd_main);
volatile int __block_new_threads = 0;
-extern size_t __default_stacksize;
-extern size_t __default_guardsize;
static FILE *volatile dummy_file = 0;
weak_alias(dummy_file, __stdin_used);
unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
| CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
| CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
- int do_sched = 0;
pthread_attr_t attr = { 0 };
- struct start_sched_args ssa;
+ sigset_t set;
+ volatile int err = -1;
if (!libc.can_do_threads) return ENOSYS;
self = __pthread_self();
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->detach_state = DT_DETACHED;
- flags -= CLONE_CHILD_CLEARTID;
} else {
new->detach_state = DT_JOINABLE;
}
- if (attr._a_sched) {
- 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->detach_state);
-
- __release_ptc();
+ /* Setup argument structure for the new thread on its stack.
+ * It's safe to access from the caller only until the thread
+ * list is unlocked. */
+ stack -= (uintptr_t)stack % sizeof(uintptr_t);
+ stack -= sizeof(struct start_args);
+ struct start_args *args = (void *)stack;
+ args->start_func = entry;
+ args->start_arg = arg;
+ if (attr._a_sched) {
+ args->attr = &attr;
+ args->perr = &err;
+ } else {
+ args->attr = 0;
+ args->perr = 0;
+ }
- if (do_sched) {
- __restore_sigs(&ssa.mask);
+ /* Application signals (but not the synccall signal) must be
+ * blocked before the thread list lock can be taken, to ensure
+ * that the lock is AS-safe. */
+ __block_app_sigs(&set);
+
+ /* Ensure SIGCANCEL is unblocked in new thread. This requires
+ * working with a copy of the set so we can restore the
+ * original mask in the calling thread. */
+ memcpy(&args->sig_mask, &set, sizeof args->sig_mask);
+ args->sig_mask[(SIGCANCEL-1)/8/sizeof(long)] &=
+ ~(1UL<<((SIGCANCEL-1)%(8*sizeof(long))));
+
+ __tl_lock();
+ libc.threads_minus_1++;
+ ret = __clone((c11 ? start_c11 : start), stack, flags, args, &new->tid, TP_ADJ(new), &__thread_list_lock);
+
+ /* If clone succeeded, new thread must be linked on the thread
+ * list before unlocking it, even if scheduling may still fail. */
+ if (ret >= 0) {
+ new->next = self->next;
+ new->prev = self;
+ new->next->prev = new;
+ new->prev->next = new;
}
+ __tl_unlock();
+ __restore_sigs(&set);
+ __release_ptc();
if (ret < 0) {
- a_dec(&libc.threads_minus_1);
+ libc.threads_minus_1--;
if (map) __munmap(map, size);
return EAGAIN;
}
- if (do_sched) {
- __futexwait(&ssa.futex, -1, 1);
- ret = ssa.futex;
+ if (attr._a_sched) {
+ if (a_cas(&err, -1, -2)==-1)
+ __wait(&err, 0, -2, 1);
+ ret = err;
if (ret) return ret;
}
projects / musl / blobdiff