diff options
Diffstat (limited to 'library/std/src/sys/pal/unix')
| -rw-r--r-- | library/std/src/sys/pal/unix/mod.rs | 1 | ||||
| -rw-r--r-- | library/std/src/sys/pal/unix/sync/condvar.rs | 172 | ||||
| -rw-r--r-- | library/std/src/sys/pal/unix/sync/mod.rs | 16 | ||||
| -rw-r--r-- | library/std/src/sys/pal/unix/sync/mutex.rs | 133 |
4 files changed, 322 insertions, 0 deletions
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs index 4fe18daa204..8eaa50d7f81 100644 --- a/library/std/src/sys/pal/unix/mod.rs +++ b/library/std/src/sys/pal/unix/mod.rs @@ -27,6 +27,7 @@ pub mod pipe; pub mod process; pub mod stack_overflow; pub mod stdio; +pub mod sync; pub mod thread; pub mod thread_parking; pub mod time; diff --git a/library/std/src/sys/pal/unix/sync/condvar.rs b/library/std/src/sys/pal/unix/sync/condvar.rs new file mode 100644 index 00000000000..13eeba9c880 --- /dev/null +++ b/library/std/src/sys/pal/unix/sync/condvar.rs @@ -0,0 +1,172 @@ +use super::Mutex; +use crate::cell::UnsafeCell; +use crate::pin::Pin; +#[cfg(not(target_os = "nto"))] +use crate::sys::pal::time::TIMESPEC_MAX; +#[cfg(target_os = "nto")] +use crate::sys::pal::time::TIMESPEC_MAX_CAPPED; +use crate::sys::pal::time::Timespec; +use crate::time::Duration; + +pub struct Condvar { + inner: UnsafeCell<libc::pthread_cond_t>, +} + +impl Condvar { + pub fn new() -> Condvar { + Condvar { inner: UnsafeCell::new(libc::PTHREAD_COND_INITIALIZER) } + } + + #[inline] + fn raw(&self) -> *mut libc::pthread_cond_t { + self.inner.get() + } + + /// # Safety + /// `init` must have been called. + #[inline] + pub unsafe fn notify_one(self: Pin<&Self>) { + let r = unsafe { libc::pthread_cond_signal(self.raw()) }; + debug_assert_eq!(r, 0); + } + + /// # Safety + /// `init` must have been called. + #[inline] + pub unsafe fn notify_all(self: Pin<&Self>) { + let r = unsafe { libc::pthread_cond_broadcast(self.raw()) }; + debug_assert_eq!(r, 0); + } + + /// # Safety + /// * `init` must have been called. + /// * `mutex` must be locked by the current thread. + /// * This condition variable may only be used with the same mutex. + #[inline] + pub unsafe fn wait(self: Pin<&Self>, mutex: Pin<&Mutex>) { + let r = unsafe { libc::pthread_cond_wait(self.raw(), mutex.raw()) }; + debug_assert_eq!(r, 0); + } + + /// # Safety + /// * `init` must have been called. + /// * `mutex` must be locked by the current thread. + /// * This condition variable may only be used with the same mutex. + pub unsafe fn wait_timeout(&self, mutex: Pin<&Mutex>, dur: Duration) -> bool { + let mutex = mutex.raw(); + + // OSX implementation of `pthread_cond_timedwait` is buggy + // with super long durations. When duration is greater than + // 0x100_0000_0000_0000 seconds, `pthread_cond_timedwait` + // in macOS Sierra returns error 316. + // + // This program demonstrates the issue: + // https://gist.github.com/stepancheg/198db4623a20aad2ad7cddb8fda4a63c + // + // To work around this issue, the timeout is clamped to 1000 years. + #[cfg(target_vendor = "apple")] + let dur = Duration::min(dur, Duration::from_secs(1000 * 365 * 86400)); + + let timeout = Timespec::now(Self::CLOCK).checked_add_duration(&dur); + + #[cfg(not(target_os = "nto"))] + let timeout = timeout.and_then(|t| t.to_timespec()).unwrap_or(TIMESPEC_MAX); + + #[cfg(target_os = "nto")] + let timeout = timeout.and_then(|t| t.to_timespec_capped()).unwrap_or(TIMESPEC_MAX_CAPPED); + + let r = unsafe { libc::pthread_cond_timedwait(self.raw(), mutex, &timeout) }; + assert!(r == libc::ETIMEDOUT || r == 0); + r == 0 + } +} + +#[cfg(not(any( + target_os = "android", + target_vendor = "apple", + target_os = "espidf", + target_os = "horizon", + target_os = "l4re", + target_os = "redox", + target_os = "teeos", +)))] +impl Condvar { + pub const PRECISE_TIMEOUT: bool = true; + const CLOCK: libc::clockid_t = libc::CLOCK_MONOTONIC; + + /// # Safety + /// May only be called once. + pub unsafe fn init(self: Pin<&mut Self>) { + use crate::mem::MaybeUninit; + + struct AttrGuard<'a>(pub &'a mut MaybeUninit<libc::pthread_condattr_t>); + impl Drop for AttrGuard<'_> { + fn drop(&mut self) { + unsafe { + let result = libc::pthread_condattr_destroy(self.0.as_mut_ptr()); + assert_eq!(result, 0); + } + } + } + + unsafe { + let mut attr = MaybeUninit::<libc::pthread_condattr_t>::uninit(); + let r = libc::pthread_condattr_init(attr.as_mut_ptr()); + assert_eq!(r, 0); + let attr = AttrGuard(&mut attr); + let r = libc::pthread_condattr_setclock(attr.0.as_mut_ptr(), Self::CLOCK); + assert_eq!(r, 0); + let r = libc::pthread_cond_init(self.raw(), attr.0.as_ptr()); + assert_eq!(r, 0); + } + } +} + +// `pthread_condattr_setclock` is unfortunately not supported on these platforms. +#[cfg(any( + target_os = "android", + target_vendor = "apple", + target_os = "espidf", + target_os = "horizon", + target_os = "l4re", + target_os = "redox", + target_os = "teeos", +))] +impl Condvar { + pub const PRECISE_TIMEOUT: bool = false; + const CLOCK: libc::clockid_t = libc::CLOCK_REALTIME; + + /// # Safety + /// May only be called once. + pub unsafe fn init(self: Pin<&mut Self>) { + if cfg!(any(target_os = "espidf", target_os = "horizon", target_os = "teeos")) { + // NOTE: ESP-IDF's PTHREAD_COND_INITIALIZER support is not released yet + // So on that platform, init() should always be called. + // + // Similar story for the 3DS (horizon) and for TEEOS. + let r = unsafe { libc::pthread_cond_init(self.raw(), crate::ptr::null()) }; + assert_eq!(r, 0); + } + } +} + +impl !Unpin for Condvar {} + +unsafe impl Sync for Condvar {} +unsafe impl Send for Condvar {} + +impl Drop for Condvar { + #[inline] + fn drop(&mut self) { + let r = unsafe { libc::pthread_cond_destroy(self.raw()) }; + if cfg!(target_os = "dragonfly") { + // On DragonFly pthread_cond_destroy() returns EINVAL if called on + // a condvar that was just initialized with + // libc::PTHREAD_COND_INITIALIZER. Once it is used or + // pthread_cond_init() is called, this behaviour no longer occurs. + debug_assert!(r == 0 || r == libc::EINVAL); + } else { + debug_assert_eq!(r, 0); + } + } +} diff --git a/library/std/src/sys/pal/unix/sync/mod.rs b/library/std/src/sys/pal/unix/sync/mod.rs new file mode 100644 index 00000000000..b430ff5d8ef --- /dev/null +++ b/library/std/src/sys/pal/unix/sync/mod.rs @@ -0,0 +1,16 @@ +#![cfg(not(any( + target_os = "linux", + target_os = "android", + all(target_os = "emscripten", target_feature = "atomics"), + target_os = "freebsd", + target_os = "openbsd", + target_os = "dragonfly", + target_os = "fuchsia", +)))] +#![forbid(unsafe_op_in_unsafe_fn)] + +mod condvar; +mod mutex; + +pub use condvar::Condvar; +pub use mutex::Mutex; diff --git a/library/std/src/sys/pal/unix/sync/mutex.rs b/library/std/src/sys/pal/unix/sync/mutex.rs new file mode 100644 index 00000000000..8ffd375bf91 --- /dev/null +++ b/library/std/src/sys/pal/unix/sync/mutex.rs @@ -0,0 +1,133 @@ +use super::super::cvt_nz; +use crate::cell::UnsafeCell; +use crate::io::Error; +use crate::mem::MaybeUninit; +use crate::pin::Pin; + +pub struct Mutex { + inner: UnsafeCell<libc::pthread_mutex_t>, +} + +impl Mutex { + pub fn new() -> Mutex { + Mutex { inner: UnsafeCell::new(libc::PTHREAD_MUTEX_INITIALIZER) } + } + + pub(super) fn raw(&self) -> *mut libc::pthread_mutex_t { + self.inner.get() + } + + /// # Safety + /// Must only be called once. + pub unsafe fn init(self: Pin<&mut Self>) { + // Issue #33770 + // + // A pthread mutex initialized with PTHREAD_MUTEX_INITIALIZER will have + // a type of PTHREAD_MUTEX_DEFAULT, which has undefined behavior if you + // try to re-lock it from the same thread when you already hold a lock + // (https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_mutex_init.html). + // This is the case even if PTHREAD_MUTEX_DEFAULT == PTHREAD_MUTEX_NORMAL + // (https://github.com/rust-lang/rust/issues/33770#issuecomment-220847521) -- in that + // case, `pthread_mutexattr_settype(PTHREAD_MUTEX_DEFAULT)` will of course be the same + // as setting it to `PTHREAD_MUTEX_NORMAL`, but not setting any mode will result in + // a Mutex where re-locking is UB. + // + // In practice, glibc takes advantage of this undefined behavior to + // implement hardware lock elision, which uses hardware transactional + // memory to avoid acquiring the lock. While a transaction is in + // progress, the lock appears to be unlocked. This isn't a problem for + // other threads since the transactional memory will abort if a conflict + // is detected, however no abort is generated when re-locking from the + // same thread. + // + // Since locking the same mutex twice will result in two aliasing &mut + // references, we instead create the mutex with type + // PTHREAD_MUTEX_NORMAL which is guaranteed to deadlock if we try to + // re-lock it from the same thread, thus avoiding undefined behavior. + unsafe { + let mut attr = MaybeUninit::<libc::pthread_mutexattr_t>::uninit(); + cvt_nz(libc::pthread_mutexattr_init(attr.as_mut_ptr())).unwrap(); + let attr = AttrGuard(&mut attr); + cvt_nz(libc::pthread_mutexattr_settype( + attr.0.as_mut_ptr(), + libc::PTHREAD_MUTEX_NORMAL, + )) + .unwrap(); + cvt_nz(libc::pthread_mutex_init(self.raw(), attr.0.as_ptr())).unwrap(); + } + } + + /// # Safety + /// * If `init` was not called, reentrant locking causes undefined behaviour. + /// * Destroying a locked mutex causes undefined behaviour. + pub unsafe fn lock(self: Pin<&Self>) { + #[cold] + #[inline(never)] + fn fail(r: i32) -> ! { + let error = Error::from_raw_os_error(r); + panic!("failed to lock mutex: {error}"); + } + + let r = unsafe { libc::pthread_mutex_lock(self.raw()) }; + // As we set the mutex type to `PTHREAD_MUTEX_NORMAL` above, we expect + // the lock call to never fail. Unfortunately however, some platforms + // (Solaris) do not conform to the standard, and instead always provide + // deadlock detection. How kind of them! Unfortunately that means that + // we need to check the error code here. To save us from UB on other + // less well-behaved platforms in the future, we do it even on "good" + // platforms like macOS. See #120147 for more context. + if r != 0 { + fail(r) + } + } + + /// # Safety + /// * If `init` was not called, reentrant locking causes undefined behaviour. + /// * Destroying a locked mutex causes undefined behaviour. + pub unsafe fn try_lock(self: Pin<&Self>) -> bool { + unsafe { libc::pthread_mutex_trylock(self.raw()) == 0 } + } + + /// # Safety + /// The mutex must be locked by the current thread. + pub unsafe fn unlock(self: Pin<&Self>) { + let r = unsafe { libc::pthread_mutex_unlock(self.raw()) }; + debug_assert_eq!(r, 0); + } +} + +impl !Unpin for Mutex {} + +unsafe impl Send for Mutex {} +unsafe impl Sync for Mutex {} + +impl Drop for Mutex { + fn drop(&mut self) { + // SAFETY: + // If `lock` or `init` was called, the mutex must have been pinned, so + // it is still at the same location. Otherwise, `inner` must contain + // `PTHREAD_MUTEX_INITIALIZER`, which is valid at all locations. Thus, + // this call always destroys a valid mutex. + let r = unsafe { libc::pthread_mutex_destroy(self.raw()) }; + if cfg!(target_os = "dragonfly") { + // On DragonFly pthread_mutex_destroy() returns EINVAL if called on a + // mutex that was just initialized with libc::PTHREAD_MUTEX_INITIALIZER. + // Once it is used (locked/unlocked) or pthread_mutex_init() is called, + // this behaviour no longer occurs. + debug_assert!(r == 0 || r == libc::EINVAL); + } else { + debug_assert_eq!(r, 0); + } + } +} + +struct AttrGuard<'a>(pub &'a mut MaybeUninit<libc::pthread_mutexattr_t>); + +impl Drop for AttrGuard<'_> { + fn drop(&mut self) { + unsafe { + let result = libc::pthread_mutexattr_destroy(self.0.as_mut_ptr()); + assert_eq!(result, 0); + } + } +} |