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Date: Thu, 16 Aug 2018 01:09:33 +0200
From: Piotr Tworek <>
Cc: Piotr Tworek <>
Subject: [PATCH] Don't return new thread ID from pthread_create.

From: Piotr Tworek <>

According to documentation pthread_create is supposed to return 0 on
success or error code in case of failure. Unfortunately this is not
always the case in musl. In case the application has called
pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED),
pthread_create will return new thread ID. To make matters worse such non
zero value does not mean thread creation failed. Its quite the oposite.
Thread was created succesfully and start routine passed to pthread_create
will actually get invoked.

To fix the problem simply drop the return statement from the last
if statement in musl's pthread_create. The value currently being returned
from there is a return code from __clone. Negative values indicating
failure have already been handled by previous if statement and positive
value indicates everything went correctly and pthread_create should return 0.
 src/thread/pthread_create.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 2df2e9f9..792cb42e 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -306,7 +306,6 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
 	if (do_sched) {
 		__futexwait(&ssa.futex, -1, 1);
-		if (ret) return ret;
 	*res = new;

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