Auto merge of #2899 - saethlin:measureme-cleanup, r=RalfJung

Try to ensure measureme output is valid when the interpreter is interrupted

Dropping our `measureme::Profiler` will have the profiler flush its output buffer and write out its string table. If the profiler's `Drop` impl does not run, the output file is not usable.

This approach has zero runtime overhead.

Author: bors

Cargo.lock

@@ -29,6 +29,7 @@ smallvec = "1.7"
 # for more information.
 rustc-workspace-hack = "1.0.0"
 measureme = "10.0.0"
+ctrlc = "3.2.5"
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"

Cargo.toml

@@ -3,6 +3,7 @@
 use std::cell::RefCell;
 use std::collections::hash_map::Entry;
 use std::num::TryFromIntError;
+use std::sync::atomic::{AtomicBool, Ordering::Relaxed};
 use std::task::Poll;
 use std::time::{Duration, SystemTime};
 
@@ -1012,8 +1013,24 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
     /// Run the core interpreter loop. Returns only when an interrupt occurs (an error or program
     /// termination).
     fn run_threads(&mut self) -> InterpResult<'tcx, !> {
+        static SIGNALED: AtomicBool = AtomicBool::new(false);
+        ctrlc::set_handler(move || {
+            // Indicate that we have ben signaled to stop. If we were already signaled, exit
+            // immediately. In our interpreter loop we try to consult this value often, but if for
+            // whatever reason we don't get to that check or the cleanup we do upon finding that
+            // this bool has become true takes a long time, the exit here will promptly exit the
+            // process on the second Ctrl-C.
+            if SIGNALED.swap(true, Relaxed) {
+                std::process::exit(1);
+            }
+        })
+        .unwrap();
         let this = self.eval_context_mut();
         loop {
+            if SIGNALED.load(Relaxed) {
+                this.machine.handle_abnormal_termination();
+                std::process::exit(1);
+            }
             match this.machine.threads.schedule(&this.machine.clock)? {
                 SchedulingAction::ExecuteStep => {
                     if !this.step()? {

src/concurrency/thread.rs

@@ -713,6 +713,15 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
         let def_id = frame.instance.def_id();
         def_id.is_local() || self.local_crates.contains(&def_id.krate)
     }
+
+    /// Called when the interpreter is going to shut down abnormally, such as due to a Ctrl-C.
+    pub(crate) fn handle_abnormal_termination(&mut self) {
+        // All strings in the profile data are stored in a single string table which is not
+        // written to disk until the profiler is dropped. If the interpreter exits without dropping
+        // the profiler, it is not possible to interpret the profile data and all measureme tools
+        // will panic when given the file.
+        drop(self.profiler.take());
+    }
 }
 
 impl VisitTags for MiriMachine<'_, '_> {