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feat: Allow fallback to signal backend
As pidfd isn't available in older versions of Linux that Rust still supports, this is necessary for running on older Linux. In addition, signals tests are still kept in CI. Signed-off-by: John Nunley <dev@notgull.net>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,221 @@ | ||
| //! The underlying system reaper. | ||
| //! | ||
| //! There are two backends: | ||
| //! | ||
| //! - signal, which waits for SIGCHLD. | ||
| //! - wait, which waits directly on a process handle. | ||
| //! | ||
| //! "wait" is preferred, but is not available on all supported Linuxes. So we | ||
| //! test to see if pidfd is supported first. If it is, we use wait. If not, we use | ||
| //! signal. | ||
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| #![allow(irrefutable_let_patterns)] | ||
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| /// Enable the waiting reaper. | ||
| #[cfg(any(target_os = "linux", target_os = "android"))] | ||
| macro_rules! cfg_wait { | ||
| ($($tt:tt)*) => {$($tt)*}; | ||
| } | ||
|
|
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| /// Enable the waiting reaper. | ||
| #[cfg(not(any(target_os = "linux", target_os = "android")))] | ||
| macro_rules! cfg_wait { | ||
| ($($tt:tt)*) => {}; | ||
| } | ||
|
|
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| /// Enable signals. | ||
| macro_rules! cfg_signal { | ||
| ($($tt:tt)*) => {$($tt)*}; | ||
| } | ||
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| cfg_wait! { | ||
| mod wait; | ||
| } | ||
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| cfg_signal! { | ||
| mod signal; | ||
| } | ||
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| use std::io; | ||
| use std::sync::Mutex; | ||
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| /// The underlying system reaper. | ||
| pub(crate) enum Reaper { | ||
| #[cfg(any(target_os = "linux", target_os = "android"))] | ||
| /// The reaper based on the wait backend. | ||
| Wait(wait::Reaper), | ||
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| /// The reaper based on the signal backend. | ||
| Signal(signal::Reaper), | ||
| } | ||
|
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| /// The wrapper around a child. | ||
| pub(crate) enum ChildGuard { | ||
| #[cfg(any(target_os = "linux", target_os = "android"))] | ||
| /// The child guard based on the wait backend. | ||
| Wait(wait::ChildGuard), | ||
|
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| /// The child guard based on the signal backend. | ||
| Signal(signal::ChildGuard), | ||
| } | ||
|
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| /// A lock on the reaper. | ||
| pub(crate) enum Lock { | ||
| #[cfg(any(target_os = "linux", target_os = "android"))] | ||
| /// The wait-based reaper needs no lock. | ||
| Wait, | ||
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| /// The lock for the signal-based reaper. | ||
| Signal(signal::Lock), | ||
| } | ||
|
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| impl Reaper { | ||
| /// Create a new reaper. | ||
| pub(crate) fn new() -> Self { | ||
| cfg_wait! { | ||
| if wait::available() && !cfg!(async_process_force_signal_backend) { | ||
| return Self::Wait(wait::Reaper::new()); | ||
| } | ||
| } | ||
|
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| // Return the signal-based reaper. | ||
| cfg_signal! { | ||
| return Self::Signal(signal::Reaper::new()); | ||
| } | ||
|
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| #[allow(unreachable_code)] | ||
| { | ||
| panic!("neither the signal backend nor the waiter backend is available") | ||
| } | ||
| } | ||
|
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| /// Lock the driver thread. | ||
| /// | ||
| /// This makes it so only one thread can reap at once. | ||
| pub(crate) async fn lock(&'static self) -> Lock { | ||
| cfg_wait! { | ||
| if let Self::Wait(_this) = self { | ||
| // No locking needed. | ||
| return Lock::Wait; | ||
| } | ||
| } | ||
|
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| cfg_signal! { | ||
| if let Self::Signal(this) = self { | ||
| // We need to lock. | ||
| return Lock::Signal(this.lock().await); | ||
| } | ||
| } | ||
|
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||
| unreachable!() | ||
| } | ||
|
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| /// Reap zombie processes forever. | ||
| pub(crate) async fn reap(&'static self, lock: Lock) -> ! { | ||
| cfg_wait! { | ||
| if let (Self::Wait(this), Lock::Wait) = (self, &lock) { | ||
| return this.reap().await; | ||
| } | ||
| } | ||
|
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| cfg_signal! { | ||
| if let (Self::Signal(this), Lock::Signal(lock)) = (self, lock) { | ||
| return this.reap(lock).await; | ||
| } | ||
| } | ||
|
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| unreachable!() | ||
| } | ||
|
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| /// Register a child into this reaper. | ||
| pub(crate) fn register(&'static self, child: std::process::Child) -> io::Result<ChildGuard> { | ||
| cfg_wait! { | ||
| if let Self::Wait(this) = self { | ||
| return this.register(child).map(ChildGuard::Wait); | ||
| } | ||
| } | ||
|
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| cfg_signal! { | ||
| if let Self::Signal(this) = self { | ||
| return this.register(child).map(ChildGuard::Signal); | ||
| } | ||
| } | ||
|
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| unreachable!() | ||
| } | ||
|
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| /// Wait for the inner child to complete. | ||
| pub(crate) async fn status( | ||
| &'static self, | ||
| child: &Mutex<crate::ChildGuard>, | ||
| ) -> io::Result<std::process::ExitStatus> { | ||
| cfg_wait! { | ||
| if let Self::Wait(this) = self { | ||
| return this.status(child).await; | ||
| } | ||
| } | ||
|
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| cfg_signal! { | ||
| if let Self::Signal(this) = self { | ||
| return this.status(child).await; | ||
| } | ||
| } | ||
|
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| unreachable!() | ||
| } | ||
|
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| /// Do we have any registered zombie processes? | ||
| pub(crate) fn has_zombies(&'static self) -> bool { | ||
| cfg_wait! { | ||
| if let Self::Wait(this) = self { | ||
| return this.has_zombies(); | ||
| } | ||
| } | ||
|
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| cfg_signal! { | ||
| if let Self::Signal(this) = self { | ||
| return this.has_zombies(); | ||
| } | ||
| } | ||
|
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| unreachable!() | ||
| } | ||
| } | ||
|
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| impl ChildGuard { | ||
| /// Get a reference to the inner process. | ||
| pub(crate) fn get_mut(&mut self) -> &mut std::process::Child { | ||
| cfg_wait! { | ||
| if let Self::Wait(this) = self { | ||
| return this.get_mut(); | ||
| } | ||
| } | ||
|
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| cfg_signal! { | ||
| if let Self::Signal(this) = self { | ||
| return this.get_mut(); | ||
| } | ||
| } | ||
|
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| unreachable!() | ||
| } | ||
|
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| /// Start reaping this child process. | ||
| pub(crate) fn reap(&mut self, reaper: &'static Reaper) { | ||
| cfg_wait! { | ||
| if let (Self::Wait(this), Reaper::Wait(reaper)) = (&mut *self, reaper) { | ||
| this.reap(reaper); | ||
| return; | ||
| } | ||
| } | ||
|
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| cfg_signal! { | ||
| if let (Self::Signal(this), Reaper::Signal(reaper)) = (self, reaper) { | ||
| this.reap(reaper); | ||
| return; | ||
| } | ||
| } | ||
|
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||
| unreachable!() | ||
| } | ||
| } |
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