X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=src%2Fthread%2Fpthread_create.c;h=10f1b7d8cd39605d42dfea19370c88b9183e6036;hb=4554f155dd23a65fcdfd39f1d5af8af55ba37694;hp=edaf9a6e2022acfec53dff13b6b535acebfacbea;hpb=dd0a23dd9e157624347fdcc9dca452675b93da70;p=musl diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c index edaf9a6e..10f1b7d8 100644 --- a/src/thread/pthread_create.c +++ b/src/thread/pthread_create.c @@ -72,12 +72,13 @@ _Noreturn void __pthread_exit(void *result) /* 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. */ + * joinable threads it's a valid usage that must be handled. + * Signals must be blocked since pthread_kill must be AS-safe. */ + __block_app_sigs(&set); LOCK(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); + /* The thread list lock must be AS-safe, and thus depends on + * application signals being blocked above. */ __tl_lock(); /* If this is the only thread in the list, don't proceed with @@ -85,19 +86,12 @@ _Noreturn void __pthread_exit(void *result) * signal state to prepare for exit to call atexit handlers. */ if (self->next == self) { __tl_unlock(); - __restore_sigs(&set); UNLOCK(self->killlock); + __restore_sigs(&set); 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; + /* At this point we are committed to thread termination. */ /* Process robust list in userspace to handle non-pshared mutexes * and the detached thread case where the robust list head will @@ -121,6 +115,16 @@ _Noreturn void __pthread_exit(void *result) __do_orphaned_stdio_locks(); __dl_thread_cleanup(); + /* Last, unlink 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. + * This needs to happen after any possible calls to LOCK() that might + * skip locking if process appears single-threaded. */ + if (!--libc.threads_minus_1) libc.need_locks = -1; + self->next->prev = self->prev; + self->prev->next = self->next; + self->prev = self->next = self; + /* 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); @@ -172,23 +176,20 @@ void __do_cleanup_pop(struct __ptcb *cb) struct start_args { void *(*start_func)(void *); void *start_arg; - pthread_attr_t *attr; - volatile int *perr; + volatile int control; unsigned long sig_mask[_NSIG/8/sizeof(long)]; }; static int start(void *p) { 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); + int state = args->control; + if (state) { + if (a_cas(&args->control, 1, 2)==1) + __wait(&args->control, 0, 2, 1); + if (args->control) { + __syscall(SYS_set_tid_address, &args->control); + for (;;) __syscall(SYS_exit, 0); } } __syscall(SYS_rt_sigprocmask, SIG_SETMASK, &args->sig_mask, 0, _NSIG/8); @@ -233,7 +234,6 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED; pthread_attr_t attr = { 0 }; sigset_t set; - volatile int err = -1; if (!libc.can_do_threads) return ENOSYS; self = __pthread_self(); @@ -325,13 +325,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att 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; - } + args->control = attr._a_sched ? 1 : 0; /* Application signals (but not the synccall signal) must be * blocked before the thread list lock can be taken, to ensure @@ -346,18 +340,31 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att ~(1UL<<((SIGCANCEL-1)%(8*sizeof(long)))); __tl_lock(); - libc.threads_minus_1++; + if (!libc.threads_minus_1++) libc.need_locks = 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. */ + /* All clone failures translate to EAGAIN. If explicit scheduling + * was requested, attempt it before unlocking the thread list so + * that the failed thread is never exposed and so that we can + * clean up all transient resource usage before returning. */ + if (ret < 0) { + ret = -EAGAIN; + } else if (attr._a_sched) { + ret = __syscall(SYS_sched_setscheduler, + new->tid, attr._a_policy, &attr._a_prio); + if (a_swap(&args->control, ret ? 3 : 0)==2) + __wake(&args->control, 1, 1); + if (ret) + __wait(&args->control, 0, 3, 0); + } + if (ret >= 0) { new->next = self->next; new->prev = self; new->next->prev = new; new->prev->next = new; } else { - libc.threads_minus_1--; + if (!--libc.threads_minus_1) libc.need_locks = 0; } __tl_unlock(); __restore_sigs(&set); @@ -365,14 +372,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att if (ret < 0) { if (map) __munmap(map, size); - return EAGAIN; - } - - if (attr._a_sched) { - if (a_cas(&err, -1, -2)==-1) - __wait(&err, 0, -2, 1); - ret = err; - if (ret) return ret; + return -ret; } *res = new;