Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Fix self profiler ICE on Windows #56170

Merged
merged 2 commits into from
Nov 25, 2018
Merged

Fix self profiler ICE on Windows #56170

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
b319715
Disable the self-profiler unless the `-Z self-profile` flag is set
wesleywiser Nov 22, 2018
dce1c45
[Windows] Work around non-monotonic clocks in the self-profiler
wesleywiser Nov 22, 2018
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 4 additions & 2 deletions src/librustc/session/mod.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -826,8 +826,10 @@ impl Session {
}

pub fn profiler<F: FnOnce(&mut SelfProfiler) -> ()>(&self, f: F) {
let mut profiler = self.self_profiling.borrow_mut();
f(&mut profiler);
if self.opts.debugging_opts.self_profile {
let mut profiler = self.self_profiling.borrow_mut();
f(&mut profiler);
}
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Was this change needed? (Not that it's wrong, just surprised it wasn't already the case).

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Not needed per se. It wasn't already the case because we showed a very small amount of overhead from turning on the profiler. I think it's probably best to make it opt-in though.

}

pub fn print_profiler_results(&self) {
Expand Down
17 changes: 15 additions & 2 deletions src/librustc/util/profiling.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ use session::config::Options;

use std::fs;
use std::io::{self, StdoutLock, Write};
use std::time::Instant;
use std::time::{Duration, Instant};

macro_rules! define_categories {
($($name:ident,)*) => {
Expand Down Expand Up @@ -197,7 +197,20 @@ impl SelfProfiler {
}

fn stop_timer(&mut self) -> u64 {
let elapsed = self.current_timer.elapsed();
let elapsed = if cfg!(windows) {
// On Windows, timers don't always appear to be monotonic (see #51648)
// which can lead to panics when calculating elapsed time.
// Work around this by testing to see if the current time is less than
// our recorded time, and if it is, just returning 0.
let now = Instant::now();
if self.current_timer >= now {
Duration::new(0, 0)
} else {
self.current_timer.elapsed()
Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Shouldn't this line (209) be changed to do now - self.current_timer instead? I think right now it's susceptible to the same error the workaround is meant to prevent. Since Instant::elapsed will call Instant::now again, which could be inaccurate and won't be double-checked like the variable now just was.

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

That seems like a reasonable change to me

}
} else {
self.current_timer.elapsed()
};

self.current_timer = Instant::now();

Expand Down