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tracer: 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 21:44:42 +00:00 committed by Liu Wei
parent ca02a69fdf
commit 93883681be
1 changed files with 13 additions and 6 deletions
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19
tracer/src/tracer.rs
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@ -30,6 +30,7 @@ impl Tracer {
fn end(&self) {
let end = Instant::now();
// SAFETY: FFI call
let path = format!("cloud-hypervisor-{}.trace", unsafe { libc::getpid() });
let mut file = File::create(&path).unwrap();
@ -105,11 +106,14 @@ struct TraceEvent {
pub fn trace_point_log(event: &'static str) {
let trace_event = TraceEvent {
// SAFETY: start has been initialised as part of initialising the value of TRACER
timestamp: Instant::now().duration_since(unsafe { TRACER.get().unwrap().start }),
event,
end_timestamp: None,
// SAFETY: thread_depth accesses current thread only specific data
depth: unsafe { TRACER.get().unwrap().thread_depth() },
};
// SAFETY: add_event accesses current thread only specific data
unsafe {
TRACER.get_mut().unwrap().add_event(trace_event);
}
@ -122,6 +126,7 @@ pub struct TraceBlock {
impl TraceBlock {
pub fn new(event: &'static str) -> Self {
// SAFETY: increase_thread_depth accesses current thread only specific data
unsafe {
TRACER.get_mut().unwrap().increase_thread_depth();
}
@ -134,16 +139,16 @@ impl TraceBlock {
impl Drop for TraceBlock {
fn drop(&mut self) {
// SAFETY: start has been initialised as part of initialising the value of TRACER
let start = unsafe { TRACER.get().unwrap().start };
let trace_event = TraceEvent {
timestamp: self
.start
.duration_since(unsafe { TRACER.get().unwrap().start }),
timestamp: self.start.duration_since(start),
event: self.event,
end_timestamp: Some(
Instant::now().duration_since(unsafe { TRACER.get().unwrap().start }),
),
end_timestamp: Some(Instant::now().duration_since(start)),
// SAFETY: thread_depth() returns a number local to the current thread
depth: unsafe { TRACER.get().unwrap().thread_depth() },
};
// SAFETY: add_event and decrease_thread_depth access current thread only specific data
unsafe {
TRACER.get_mut().unwrap().add_event(trace_event);
TRACER.get_mut().unwrap().decrease_thread_depth();
@ -166,9 +171,11 @@ macro_rules! trace_scoped {
}
pub fn end() {
// SAFETY: this is called after all other threads end
unsafe { TRACER.get().unwrap().end() }
}
pub fn start() {
// SAFETY: this is called before other threads start
unsafe { TRACER.set(Tracer::new()).unwrap() }
}