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event_monitor: add safety comments

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Signed-off-by: Wei Liu <liuwe@microsoft.com>
This commit is contained in:
Wei Liu 2022-11-16 21:22:45 +00:00 committed by Liu Wei
parent b9ad3eda27
commit b1efa5b26b
1 changed files with 4 additions and 0 deletions
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4
event_monitor/src/lib.rs
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@ -16,8 +16,10 @@ static mut MONITOR: Option<(File, Instant)> = None;
/// This function must only be called once from the main process before any threads
/// are created to avoid race conditions
pub fn set_monitor(file: File) -> Result<(), std::io::Error> {
// SAFETY: there is only one caller of this function, so MONITOR is written to only once
assert!(unsafe { MONITOR.is_none() });
let fd = file.as_raw_fd();
// SAFETY: FFI call to configure the fd
let ret = unsafe {
let mut flags = libc::fcntl(fd, libc::F_GETFL);
flags |= libc::O_NONBLOCK;
@ -26,6 +28,7 @@ pub fn set_monitor(file: File) -> Result<(), std::io::Error> {
if ret < 0 {
return Err(std::io::Error::last_os_error());
}
// SAFETY: MONITOR is None. Nobody else can hold a reference to it.
unsafe {
MONITOR = Some((file, Instant::now()));
};
@ -41,6 +44,7 @@ struct Event<'a> {
}
pub fn event_log(source: &str, event: &str, properties: Option<&HashMap<Cow<str>, Cow<str>>>) {
// SAFETY: MONITOR is always in a valid state (None or Some).
if let Some((file, start)) = unsafe { MONITOR.as_ref() } {
let e = Event {
timestamp: start.elapsed(),