Optimization: Skip pidfd_open if last call failed with ENOSYS

And fixed `test::is_pidfd_available`

Signed-off-by: Jiahao XU <[email protected]>

tokio/src/process/unix/pidfd_reaper.rs

@@ -4,7 +4,7 @@ use crate::{
  runtime::Handle,
 };
 
-use libc::{syscall, SYS_pidfd_open, PIDFD_NONBLOCK};
+use libc::{syscall, SYS_pidfd_open, __errno_location, ENOSYS, PIDFD_NONBLOCK};
 use mio::{event::Source, unix::SourceFd};
 use std::{
  fs::File,
@@ -15,6 +15,7 @@ use std::{
  os::unix::io::{AsRawFd, FromRawFd, RawFd},
  pin::Pin,
  process::ExitStatus,
+ sync::atomic::{AtomicBool, Ordering::Relaxed},
  task::{Context, Poll},
 };
 
@@ -25,9 +26,22 @@ struct Pidfd {
 
 impl Pidfd {
  fn open(pid: u32) -> Option<Pidfd> {
+ // Store false (0) to reduce executable size
+ static NO_PIDFD_SUPPORT: AtomicBool = AtomicBool::new(false);
+
+ if NO_PIDFD_SUPPORT.load(Relaxed) {
+ return None;
+ }
+
  unsafe {
  let fd = syscall(SYS_pidfd_open, pid, PIDFD_NONBLOCK);
  if fd == -1 {
+ let errno = *__errno_location();
+
+ if errno == ENOSYS {
+ NO_PIDFD_SUPPORT.store(true, Relaxed)
+ }
+
  None
  } else {
  Some(Pidfd {
@@ -196,8 +210,8 @@ mod test {
  let stdout = String::from_utf8_lossy(&stdout);
 
  let mut kernel_version_iter = stdout.split_once('-').unwrap().0.split('.');
- let major = kernel_version_iter.next().unwrap();
- let minor = kernel_version_iter.next().unwrap();
+ let major: u32 = kernel_version_iter.next().unwrap().parse().unwrap();
+ let minor: u32 = kernel_version_iter.next().unwrap().parse().unwrap();
 
  major >= 6 || (major == 5 && minor >= 10)
  }