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Date: Wed, 20 May 2020 02:09:25 +0000
From: tangyizhou <>
To: "" <>
CC: "Wanghui (John)" <>, "Huangshuai (OSLab)"
	<>, "" <>
Subject: Fix the return value of pthread_getschedparam in musl libc


>From the latest upstream, I find the return value of pthread_getschedparam() is wrong when syscall sched_getparam succeeds but sched_getscheduler fails. It is rare to see this situation. When it happens, pthread_getschedparam() will return r which must be 0, that means a success according to POSIX 2017 specification. It's wrong.

Also, POSIX 2017 specification says an error number shall be returned to indicate the error. I think returning -*policy is appropriate because syscall sched_getscheduler returns an negative error code in kernel like Linux when it fails.

Here is my patch. I want to be Cc'd on replies. Thanks.

diff --git a/src/thread/pthread_getschedparam.c b/src/thread/pthread_getschedparam.c
index 1cba073d..8203d609 100644
--- a/src/thread/pthread_getschedparam.c
+++ b/src/thread/pthread_getschedparam.c
@@ -12,6 +12,9 @@ int pthread_getschedparam(pthread_t t, int *restrict policy, struct sched_param
                if (!r) {
                        *policy = __syscall(SYS_sched_getscheduler, t->tid);
+               if (*policy < 0) {
+                       r = -*policy;
+               }
        return r;

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