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event_monitor: Replace unsound static mut MONITOR

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See discussion in https://github.com/rust-lang/rust/issues/53639.
This came up during an internal review.

Signed-off-by: Christian Blichmann <cblichmann@google.com>
(cherry picked from commit 88f3537b47)
Signed-off-by: Bo Chen <chen.bo@intel.com>
This commit is contained in:
Christian Blichmann 2023-09-14 11:19:12 +02:00 committed by Bo Chen
parent 9f316b2e50
commit ab18a923f1
3 changed files with 10 additions and 6 deletions
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1
Cargo.lock generated
View File

@ -312,6 +312,7 @@ name = "event_monitor"
version = "0.1.0"
dependencies = [
"libc",
"once_cell",
"serde",
"serde_json",
]

1
event_monitor/Cargo.toml
View File

@ -6,5 +6,6 @@ edition = "2021"
[dependencies]
libc = "0.2.138"
once_cell = "1.16.0"
serde = { version = "1.0.150", features = ["rc", "derive"] }
serde_json = "1.0.89"

14
event_monitor/src/lib.rs
View File

@ -3,6 +3,7 @@
// SPDX-License-Identifier: Apache-2.0
//
use once_cell::sync::OnceCell;
use serde::Serialize;
use std::borrow::Cow;
use std::collections::HashMap;
@ -11,12 +12,13 @@ use std::io::Write;
use std::os::unix::io::AsRawFd;
use std::time::{Duration, Instant};
static mut MONITOR: Option<(File, Instant)> = None;
static MONITOR: OnceCell<(File, Instant)> = OnceCell::new();
/// 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> {
assert!(unsafe { MONITOR.is_none() });
// There is only one caller of this function, so MONITOR is written to only once
assert!(MONITOR.get().is_none());
let fd = file.as_raw_fd();
let ret = unsafe {
let mut flags = libc::fcntl(fd, libc::F_GETFL);
@ -26,9 +28,9 @@ pub fn set_monitor(file: File) -> Result<(), std::io::Error> {
if ret < 0 {
return Err(std::io::Error::last_os_error());
}
unsafe {
MONITOR = Some((file, Instant::now()));
};
MONITOR.get_or_init(|| (file, Instant::now()));
Ok(())
}
@ -41,7 +43,7 @@ struct Event<'a> {
}
pub fn event_log(source: &str, event: &str, properties: Option<&HashMap<Cow<str>, Cow<str>>>) {
if let Some((file, start)) = unsafe { MONITOR.as_ref() } {
if let Some((file, start)) = MONITOR.get().as_ref() {
let e = Event {
timestamp: start.elapsed(),
source,