1 files changed, 45 insertions, 0 deletions
diff --git a/container/syscall.go b/container/syscall.go
index ef9fb153..e5f86cf6 100644
--- a/container/syscall.go
+++ b/container/syscall.go
@@ -3,6 +3,8 @@ package container
 import (
 	. "syscall"
 	"unsafe"
+
+	"hakurei.app/container/std"
 )
 
 // Prctl manipulates various aspects of the behavior of the calling thread or process.
@@ -41,6 +43,49 @@ func Isatty(fd int) bool {
 	return r == 0
 }
 
+// include/uapi/linux/sched.h
+const (
+	SCHED_NORMAL = iota
+	SCHED_FIFO
+	SCHED_RR
+	SCHED_BATCH
+	_ // SCHED_ISO: reserved but not implemented yet
+	SCHED_IDLE
+	SCHED_DEADLINE
+	SCHED_EXT
+)
+
+// schedParam is equivalent to struct sched_param from include/linux/sched.h.
+type schedParam struct {
+	// sched_priority
+	priority std.ScmpInt
+}
+
+// schedSetscheduler sets both the scheduling policy and parameters for the
+// thread whose ID is specified in tid. If tid equals zero, the scheduling
+// policy and parameters of the calling thread will be set.
+//
+// This function is unexported because it is [very subtle to use correctly]. The
+// function signature in libc is misleading: pid actually refers to a thread ID.
+// The glibc wrapper for this system call ignores this semantic and exposes
+// this counterintuitive behaviour.
+//
+// This function is only called from the container setup thread. Do not reuse
+// this if you do not have something similar in place!
+//
+// [very subtle to use correctly]: https://www.openwall.com/lists/musl/2016/03/01/4
+func schedSetscheduler(tid, policy int, param *schedParam) error {
+	if r, _, errno := Syscall(
+		SYS_SCHED_SETSCHEDULER,
+		uintptr(tid),
+		uintptr(policy),
+		uintptr(unsafe.Pointer(param)),
+	); r < 0 {
+		return errno
+	}
+	return nil
+}
+
 // IgnoringEINTR makes a function call and repeats it if it returns an
 // EINTR error. This appears to be required even though we install all
 // signal handlers with SA_RESTART: see #22838, #38033, #38836, #40846.