[PATCH] Cygwin: sched_setscheduler: allow changes of the priority

[Christian Franke]

sched_setscheduler(pid, sched_getscheduler(pid), param) should behave like
sched_setparam(pid, param).

--
Regards,
Christian


From a67e6679cc2bb199713b1f783d5219cb8364f5f4 Mon Sep 17 00:00:00 2001
From: Christian Franke <christian.fra...@t-online.de>
Date: Sat, 23 Nov 2024 19:50:29 +0100
Subject: [PATCH] Cygwin: sched_setscheduler: allow changes of the priority

Behave like sched_setparam() if the requested policy is identical
to the fixed value (SCHED_FIFO) returned by sched_getscheduler().

Signed-off-by: Christian Franke <christian.fra...@t-online.de>
---
 winsup/cygwin/release/3.6.0 | 3 +++
 winsup/cygwin/sched.cc      | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/release/3.6.0 b/winsup/cygwin/release/3.6.0
index 468a2ab24..09aa5376e 100644
--- a/winsup/cygwin/release/3.6.0
+++ b/winsup/cygwin/release/3.6.0
@@ -43,3 +43,6 @@ What changed:
 
 - Now using AVX/AVX2/AVX-512 instructions in signal handler does not
   break their context.
+
+- sched_setscheduler(2) allows to change the priority if the policy is
+  equal to the value returned by sched_getscheduler(2).
diff --git a/winsup/cygwin/sched.cc b/winsup/cygwin/sched.cc
index 71a1e868f..333786f44 100644
--- a/winsup/cygwin/sched.cc
+++ b/winsup/cygwin/sched.cc
@@ -399,8 +399,11 @@ int
 sched_setscheduler (pid_t pid, int policy,
                    const struct sched_param *param)
 {
+  if (policy == SCHED_FIFO) /* returned by sched_getscheduler. */
+    return sched_setparam (pid, param);
+
   /* on win32, you can't change the scheduler. Doh! */
-  set_errno (ENOSYS);
+  set_errno (EINVAL);
   return -1;
 }
 
-- 
2.45.1