Remove signalfd feature in favor of conditional compilation

Note that this is now only available for Linux as support is missing in libc
for Android (see rust-lang/libc#671).

As part of this work the SIGUSR2 signal mutex was altered to be a general
signal mutex. This is because all signal handling is shared across all threads
in the Rust test harness, so if you alter one signal, depending on whether it's
additive or may overwrite the mask for other signals, it could break the other
ones. Instead of putting this on the user, just broaden the scope of the mutex
so that any altering of signal handling needs to use it.

Author: Susurrus

Cargo.toml

@@ -17,7 +17,6 @@ exclude     = [
 
 [features]
 execvpe = []
-signalfd = []
 
 [dependencies]
 libc = "0.2.25"
@@ -36,12 +35,6 @@ nix-test = { path = "nix-test", version = "0.0.1" }
 name = "test"
 path = "test/test.rs"
 
-[[test]]
-name = "test-signalfd"
-path = "test/test_signalfd.rs"
-harness = false
-test = true
-
 [[test]]
 name = "test-mount"
 path = "test/test_mount.rs"

src/sys/mod.rs

@@ -23,8 +23,8 @@ pub mod sendfile;
 
 pub mod signal;
 
-#[cfg(any(target_os = "linux", target_os = "android"))]
-#[cfg(feature = "signalfd")]
+// FIXME: Add to Android once libc#671 lands in a release
+#[cfg(target_os = "linux")]
 pub mod signalfd;
 
 pub mod socket;

src/sys/signalfd.rs

@@ -60,12 +60,10 @@ pub fn signalfd(fd: RawFd, mask: &SigSet, flags: SfdFlags) -> Result<RawFd> {
 /// # Examples
 ///
 /// ```
-/// use nix::sys::signalfd::*;
-///
+/// # use nix::sys::signalfd::*;
+/// // Set the thread to block the SIGUSR1 signal, otherwise the default handler will be used
 /// let mut mask = SigSet::empty();
-/// mask.add(signal::SIGUSR1).unwrap();
-///
-/// // Block the signal, otherwise the default handler will be invoked instead.
+/// mask.add(signal::SIGUSR1);
 /// mask.thread_block().unwrap();
 ///
 /// // Signals are queued up on the file descriptor
@@ -74,11 +72,9 @@ pub fn signalfd(fd: RawFd, mask: &SigSet, flags: SfdFlags) -> Result<RawFd> {
 /// match sfd.read_signal() {
 ///     // we caught a signal
 ///     Ok(Some(sig)) => (),
-///
 ///     // there were no signals waiting (only happens when the SFD_NONBLOCK flag is set,
 ///     // otherwise the read_signal call blocks)
 ///     Ok(None) => (),
-///
 ///     Err(err) => (), // some error happend
 /// }
 /// ```

test/sys/mod.rs

@@ -2,6 +2,8 @@ mod test_signal;
 #[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_os = "ios",
           target_os = "netbsd", target_os = "macos", target_os = "linux"))]
 mod test_aio;
+#[cfg(target_os = "linux")]
+mod test_signalfd;
 mod test_socket;
 mod test_sockopt;
 mod test_termios;

test/sys/test_aio.rs

@@ -244,7 +244,7 @@ extern fn sigfunc(_: c_int) {
 #[cfg_attr(any(all(target_env = "musl", target_arch = "x86_64"), target_arch = "mips"), ignore)]
 fn test_write_sigev_signal() {
     #[allow(unused_variables)]
-    let m = ::SIGUSR2_MTX.lock().expect("Mutex got poisoned by another test");
+    let m = ::SIGNAL_MTX.lock().expect("Mutex got poisoned by another test");
     let sa = SigAction::new(SigHandler::Handler(sigfunc),
                             SA_RESETHAND,
                             SigSet::empty());
@@ -375,7 +375,7 @@ fn test_lio_listio_nowait() {
 #[cfg_attr(any(target_arch = "mips", target_env = "musl"), ignore)]
 fn test_lio_listio_signal() {
     #[allow(unused_variables)]
-    let m = ::SIGUSR2_MTX.lock().expect("Mutex got poisoned by another test");
+    let m = ::SIGNAL_MTX.lock().expect("Mutex got poisoned by another test");
     const INITIAL: &'static [u8] = b"abcdef123456";
     const WBUF: &'static [u8] = b"CDEF";
     let rbuf = Rc::new(vec![0; 4].into_boxed_slice());

test/sys/test_signalfd.rs

@@ -0,0 +1,26 @@
+#[test]
+fn test_signalfd() {
+    use nix::sys::signalfd::SignalFd;
+    use nix::sys::signal::{self, raise, Signal, SigSet};
+
+    // Grab the mutex for altering signals so we don't interfere with other tests.
+    #[allow(unused_variables)]
+    let m = ::SIGNAL_MTX.lock().expect("Mutex got poisoned by another test");
+
+    // Block the SIGUSR1 signal from automatic processing for this thread
+    let mut mask = SigSet::empty();
+    mask.add(signal::SIGUSR1);
+    mask.thread_block().unwrap();
+
+    let mut fd = SignalFd::new(&mask).unwrap();
+
+    // Send a SIGUSR1 signal to the current process. Note that this uses `raise` instead of `kill`
+    // because `kill` with `getpid` isn't correct during multi-threaded execution like during a
+    // cargo test session. Instead use `raise` which does the correct thing by default.
+    raise(signal::SIGUSR1).ok().expect("Error: Kill Failed");
+
+    // And now catch that same signal.
+    let res = fd.read_signal().unwrap().unwrap();
+    let signo = Signal::from_c_int(res.ssi_signo as i32).unwrap();
+    assert_eq!(signo, signal::SIGUSR1);
+}

test/test.rs

@@ -11,7 +11,7 @@ extern crate nix_test as nixtest;
 
 mod sys;
 mod test_fcntl;
-#[cfg(any(target_os = "linux"))]
+#[cfg(target_os = "linux")]
 mod test_mq;
 mod test_net;
 mod test_nix_path;
@@ -45,8 +45,8 @@ lazy_static! {
     /// Any test that creates child processes must grab this mutex, regardless
     /// of what it does with those children.
     pub static ref FORK_MTX: Mutex<()> = Mutex::new(());
-    /// Any test that registers a SIGUSR2 handler must grab this mutex
-    pub static ref SIGUSR2_MTX: Mutex<()> = Mutex::new(());
+    /// Any test that alters signal handling must grab this mutex.
+    pub static ref SIGNAL_MTX: Mutex<()> = Mutex::new(());
 }
 
 #[test]