main: Trap SIGQUIT to trigger a blackbox

The signal_hook crate makes this easy, but unfortunately insists on
hardcoding SA_RESTART. So we have to then use libc directly to patch
that out...

Still worth using signal_hook for the atomic flag helper though.

Signed-off-by: Hector Martin <marcan@marcan.st>

Cargo.lock

@@ -286,9 +286,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.137"
+version = "0.2.150"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc7fcc620a3bff7cdd7a365be3376c97191aeaccc2a603e600951e452615bf89"
+checksum = "89d92a4743f9a61002fae18374ed11e7973f530cb3a3255fb354818118b2203c"
 
 [[package]]
 name = "linux-raw-sys"
@@ -414,6 +414,25 @@ version = "1.0.152"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bb7d1f0d3021d347a83e556fc4683dea2ea09d87bccdf88ff5c12545d89d5efb"
 
+[[package]]
+name = "signal-hook"
+version = "0.3.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8621587d4798caf8eb44879d42e56b9a93ea5dcd315a6487c357130095b62801"
+dependencies = [
+ "libc",
+ "signal-hook-registry",
+]
+
+[[package]]
+name = "signal-hook-registry"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8229b473baa5980ac72ef434c4415e70c4b5e71b423043adb4ba059f89c99a1"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "simple_logger"
 version = "1.16.0"
@@ -437,7 +456,9 @@ dependencies = [
  "clap-verbosity-flag",
  "configparser",
  "json",
+ "libc",
  "log",
+ "signal-hook",
  "simple_logger",
 ]
 

Cargo.toml

@@ -15,3 +15,5 @@ clap-verbosity-flag = "2.0.0"
 simple_logger = "1.16.0"
 chrono = "0.4.31"
 json = "0.12.4"
+signal-hook = "0.3.17"
+libc = "0.2.150"

src/main.rs

@@ -11,6 +11,8 @@ use std::collections::BTreeMap;
 use std::fs;
 use std::panic::{catch_unwind, resume_unwind, AssertUnwindSafe};
 use std::path::{Path, PathBuf};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
 use std::time::Instant;
 
 use alsa::nix::errno::Errno;
@@ -88,6 +90,22 @@ impl Default for SpeakerGroup {
 fn main() {
     let args = Options::parse();
 
+    let sigquit = Arc::new(AtomicBool::new(false));
+    signal_hook::flag::register(signal_hook::consts::SIGQUIT, Arc::clone(&sigquit)).unwrap();
+    // signal_hook insists on using SA_RESTART, which we don't want. Override it.
+    unsafe {
+        let mut act: libc::sigaction = core::mem::zeroed();
+        assert!(libc::sigaction(signal_hook::consts::SIGQUIT, core::ptr::null(), &mut act) == 0);
+        act.sa_flags &= !libc::SA_RESTART;
+        assert!(
+            libc::sigaction(
+                signal_hook::consts::SIGQUIT,
+                &mut act,
+                core::ptr::null_mut()
+            ) == 0
+        );
+    }
+
     SimpleLogger::new()
         .with_level(args.verbose.log_level_filter())
         .without_timestamps()
@@ -223,10 +241,16 @@ fn main() {
         let mut once_nominal = false;
 
         loop {
+            if sigquit.load(Ordering::Relaxed) {
+                panic!("SIGQUIT received");
+            }
             // Block while we're reading into the buffer
             let read = io
                 .readi(&mut buf)
                 .or_else(|e| {
+                    if sigquit.load(Ordering::Relaxed) {
+                        panic!("SIGQUIT received");
+                    }
                     if e.errno() == Errno::ESTRPIPE {
                         warn!("Suspend detected!");
                         // Resume handling