always block signals for starting new threads, refactor start args

[musl] / src / thread / pthread_create.c

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 3da7db1..8761381 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -16,12 +16,6 @@ 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();
@@ -135,21 +129,38 @@ void __do_cleanup_pop(struct __ptcb *cb)
        __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_DYNAMIC;
+                       __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;
 }
 
@@ -182,9 +193,9 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
        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();
@@ -257,8 +268,6 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
        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;
@@ -268,38 +277,48 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
        } 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;
 
+       /* Setup argument structure for the new thread on its stack. */
+       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;
+       }
+
+       __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))));
+
        a_inc(&libc.threads_minus_1);
-       ret = __clone((c11 ? start_c11 : start), stack, flags, new, &new->tid, TP_ADJ(new), &new->detach_state);
+       ret = __clone((c11 ? start_c11 : start), stack, flags, args, &new->tid, TP_ADJ(new), &new->detach_state);
 
+       __restore_sigs(&set);
        __release_ptc();
 
-       if (do_sched) {
-               __restore_sigs(&ssa.mask);
-       }
-
        if (ret < 0) {
                a_dec(&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;
        }