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/* This example asks the rtkit service to make our thread realtime priority.
Rtkit puts a few limitations on us to let us become realtime, such as setting
RLIMIT_RTTIME correctly, hence the syscalls. */
extern crate dbus;
extern crate libc;
use std::cmp;
use libc::c_int;
use dbus::{Connection, BusType, Props, MessageItem, Message};
/* External C stuff. Currently only working for x86_64 */
#[allow(non_upper_case_globals)]
#[cfg(target_arch = "x86_64")]
static SYS_gettid: c_int = 186;
static RLIMIT_RTTIME: c_int = 15;
#[repr(C)]
#[cfg(target_arch = "x86_64")]
#[derive(Copy, Clone)]
struct rlimit {
rlim_cur: u64,
rlim_max: u64,
}
extern "C" {
fn syscall(num: c_int, ...) -> c_int;
fn getrlimit(resource: c_int, rlim: *mut rlimit) -> c_int;
fn setrlimit(resource: c_int, rlim: *const rlimit) -> c_int;
}
fn item_as_i64(i: MessageItem) -> Result<i64, Box<std::error::Error>> {
match i {
MessageItem::Int32(i) => Ok(i as i64),
MessageItem::Int64(i) => Ok(i),
_ => Err(Box::from(&*format!("Property is not integer ({:?})", i)))
}
}
fn rtkit_set_realtime(c: &Connection, thread: u64, prio: u32) -> Result<(), ::dbus::Error> {
let mut m = Message::new_method_call("org.freedesktop.RealtimeKit1", "/org/freedesktop/RealtimeKit1",
"org.freedesktop.RealtimeKit1", "MakeThreadRealtime").unwrap();
m.append_items(&[thread.into(), prio.into()]);
let mut r = try!(c.send_with_reply_and_block(m, 10000));
r.as_result().map(|_| ())
}
fn make_realtime(prio: u32) -> Result<u32, Box<std::error::Error>> {
let c = try!(Connection::get_private(BusType::System));
let p = Props::new(&c, "org.freedesktop.RealtimeKit1", "/org/freedesktop/RealtimeKit1",
"org.freedesktop.RealtimeKit1", 10000);
// Make sure we don't fail by wanting too much
let max_prio = try!(item_as_i64(try!(p.get("MaxRealtimePriority")))) as u32;
let prio = cmp::min(prio, max_prio);
// Enforce RLIMIT_RTPRIO, also a must before asking rtkit for rtprio
let max_rttime = try!(item_as_i64(try!(p.get("RTTimeNSecMax")))) as u64;
let new_limit = rlimit { rlim_cur: max_rttime, rlim_max: max_rttime };
let mut old_limit = new_limit;
if unsafe { getrlimit(RLIMIT_RTTIME, &mut old_limit) } < 0 {
return Err(Box::from("getrlimit failed"));
}
if unsafe { setrlimit(RLIMIT_RTTIME, &new_limit) } < 0 {
return Err(Box::from("setrlimit failed"));
}
// Finally, let's ask rtkit to make us realtime
let thread_id = unsafe { syscall(SYS_gettid) };
let r = rtkit_set_realtime(&c, thread_id as u64, prio);
if r.is_err() {
unsafe { setrlimit(RLIMIT_RTTIME, &old_limit) };
}
try!(r);
Ok(prio)
}
fn main() {
match make_realtime(5) {
Ok(n) => println!("Got rtprio, level {}", n),
Err(e) => println!("No rtprio: {}", e),
}
}
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