fix potential race condition in detached threads

[musl] / src / thread / pthread_create.c

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 48290d3..ae2f9e4 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -36,6 +36,8 @@ void pthread_exit(void *result)
        if (!n) exit(0);
 
        if (self->detached && self->map_base) {
+               if (self->detached == 2)
+                       __syscall(SYS_set_tid_address, 0);
                __syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1},0,8);
                __unmapself(self->map_base, self->map_size);
        }
@@ -87,6 +89,7 @@ int pthread_create(pthread_t *res, const pthread_attr_t *attr, void *(*entry)(vo
        size_t guard = DEFAULT_GUARD_SIZE;
        struct pthread *self = pthread_self(), *new;
        unsigned char *map, *stack, *tsd;
+       unsigned flags = 0x7d8f00;
 
        if (!self) return ENOSYS;
        if (!libc.threaded) {
@@ -121,7 +124,10 @@ int pthread_create(pthread_t *res, const pthread_attr_t *attr, void *(*entry)(vo
        new->start_arg = arg;
        new->self = new;
        new->tsd = (void *)tsd;
-       if (attr) new->detached = attr->_a_detach;
+       if (attr && attr->_a_detach) {
+               new->detached = 1;
+               flags -= 0x200000;
+       }
        new->unblock_cancel = self->cancel;
        new->canary = self->canary ^ (uintptr_t)&new;
        stack = (void *)new;
@@ -129,7 +135,7 @@ int pthread_create(pthread_t *res, const pthread_attr_t *attr, void *(*entry)(vo
        __synccall_lock();
 
        a_inc(&libc.threads_minus_1);
-       ret = __clone(start, stack, 0x7d8f00, new, &new->tid, new, &new->tid);
+       ret = __clone(start, stack, flags, new, &new->tid, new, &new->tid);
 
        __synccall_unlock();