fix pthread_create return value with PTHREAD_EXPLICIT_SCHED

[musl] / src / thread / pthread_create.c

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index a86b5e1..27ace2c 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -19,6 +19,12 @@ weak_alias(dummy_0, __pthread_tsd_run_dtors);
 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();
@@ -37,8 +43,6 @@ _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 +89,19 @@ _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. */
@@ -133,19 +141,6 @@ void __do_cleanup_pop(struct __ptcb *cb)
 static int start(void *p)
 {
        pthread_t self = p;
-       /* States for startlock:
-        * 0 = no need for start sync
-        * 1 = waiting for parent to do work
-        * 2 = failure in parent, child must abort
-        * 3 = success in parent, child must restore sigmask */
-       if (self->startlock[0]) {
-               __wait(self->startlock, 0, 1, 1);
-               if (self->startlock[0] == 2) {
-                       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);
@@ -170,8 +165,8 @@ static void *dummy_tsd[1] = { 0 };
 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);
@@ -196,6 +191,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
                | 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();
@@ -274,25 +270,32 @@ 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;
-               __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;
-       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();
 
        if (do_sched) {
-               __restore_sigs(new->sigmask);
+               __restore_sigs(&ssa.mask);
        }
 
        if (ret < 0) {
@@ -302,11 +305,9 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
        }
 
        if (do_sched) {
-               ret = __syscall(SYS_sched_setscheduler, new->tid,
-                       attr._a_policy, &attr._a_prio);
-               a_store(new->startlock, ret<0 ? 2 : 3);
-               __wake(new->startlock, 1, 1);
-               if (ret < 0) return -ret;
+               __futexwait(&ssa.futex, -1, 1);
+               ret = ssa.futex;
+               if (ret) return ret;
        }
 
        *res = new;