omit CLONE_PARENT flag to clone in pthread_create

CLONE_PARENT is not necessary (CLONE_THREAD provides all the useful
parts of it) and Linux treats CLONE_PARENT as an error in certain
situations, without noticing that it would be a no-op due to
CLONE_THREAD. this error case prevents, for example, use of a
multi-threaded init process and certain usages with containers.

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index fc666fc..ee6c31c 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -130,7 +130,7 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp
        struct pthread *self = pthread_self(), *new;
        unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
        unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
-               | CLONE_PARENT | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
+               | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
                | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
        int do_sched = 0;
        pthread_attr_t attr = {0};