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use crate::cell::UnsafeCell;
use crate::ptr;
use crate::sync::atomic::{AtomicPtr, Ordering::Relaxed};
use crate::sys::locks::{pthread_mutex, Mutex};
#[cfg(not(target_os = "nto"))]
use crate::sys::time::TIMESPEC_MAX;
#[cfg(target_os = "nto")]
use crate::sys::time::TIMESPEC_MAX_CAPPED;
use crate::sys_common::lazy_box::{LazyBox, LazyInit};
use crate::time::Duration;
struct AllocatedCondvar(UnsafeCell<libc::pthread_cond_t>);
pub struct Condvar {
inner: LazyBox<AllocatedCondvar>,
mutex: AtomicPtr<libc::pthread_mutex_t>,
}
#[inline]
fn raw(c: &Condvar) -> *mut libc::pthread_cond_t {
c.inner.0.get()
}
unsafe impl Send for AllocatedCondvar {}
unsafe impl Sync for AllocatedCondvar {}
impl LazyInit for AllocatedCondvar {
fn init() -> Box<Self> {
let condvar = Box::new(AllocatedCondvar(UnsafeCell::new(libc::PTHREAD_COND_INITIALIZER)));
cfg_if::cfg_if! {
if #[cfg(any(
target_os = "macos",
target_os = "ios",
target_os = "watchos",
target_os = "l4re",
target_os = "android",
target_os = "redox"
))] {
// `pthread_condattr_setclock` is unfortunately not supported on these platforms.
} else if #[cfg(any(target_os = "espidf", target_os = "horizon"))] {
// NOTE: ESP-IDF's PTHREAD_COND_INITIALIZER support is not released yet
// So on that platform, init() should always be called
// Moreover, that platform does not have pthread_condattr_setclock support,
// hence that initialization should be skipped as well
//
// Similar story for the 3DS (horizon).
let r = unsafe { libc::pthread_cond_init(condvar.0.get(), crate::ptr::null()) };
assert_eq!(r, 0);
} else {
use crate::mem::MaybeUninit;
let mut attr = MaybeUninit::<libc::pthread_condattr_t>::uninit();
let r = unsafe { libc::pthread_condattr_init(attr.as_mut_ptr()) };
assert_eq!(r, 0);
let r = unsafe { libc::pthread_condattr_setclock(attr.as_mut_ptr(), libc::CLOCK_MONOTONIC) };
assert_eq!(r, 0);
let r = unsafe { libc::pthread_cond_init(condvar.0.get(), attr.as_ptr()) };
assert_eq!(r, 0);
let r = unsafe { libc::pthread_condattr_destroy(attr.as_mut_ptr()) };
assert_eq!(r, 0);
}
}
condvar
}
}
impl Drop for AllocatedCondvar {
#[inline]
fn drop(&mut self) {
let r = unsafe { libc::pthread_cond_destroy(self.0.get()) };
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);
}
}
}
impl Condvar {
pub const fn new() -> Condvar {
Condvar { inner: LazyBox::new(), mutex: AtomicPtr::new(ptr::null_mut()) }
}
#[inline]
fn verify(&self, mutex: *mut libc::pthread_mutex_t) {
// Relaxed is okay here because we never read through `self.addr`, and only use it to
// compare addresses.
match self.mutex.compare_exchange(ptr::null_mut(), mutex, Relaxed, Relaxed) {
Ok(_) => {} // Stored the address
Err(n) if n == mutex => {} // Lost a race to store the same address
_ => panic!("attempted to use a condition variable with two mutexes"),
}
}
#[inline]
pub fn notify_one(&self) {
let r = unsafe { libc::pthread_cond_signal(raw(self)) };
debug_assert_eq!(r, 0);
}
#[inline]
pub fn notify_all(&self) {
let r = unsafe { libc::pthread_cond_broadcast(raw(self)) };
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn wait(&self, mutex: &Mutex) {
let mutex = pthread_mutex::raw(mutex);
self.verify(mutex);
let r = libc::pthread_cond_wait(raw(self), mutex);
debug_assert_eq!(r, 0);
}
// This implementation is used on systems that support pthread_condattr_setclock
// where we configure condition variable to use monotonic clock (instead of
// default system clock). This approach avoids all problems that result
// from changes made to the system time.
#[cfg(not(any(
target_os = "macos",
target_os = "ios",
target_os = "watchos",
target_os = "android",
target_os = "espidf",
target_os = "horizon"
)))]
pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
use crate::sys::time::Timespec;
let mutex = pthread_mutex::raw(mutex);
self.verify(mutex);
#[cfg(not(target_os = "nto"))]
let timeout = Timespec::now(libc::CLOCK_MONOTONIC)
.checked_add_duration(&dur)
.and_then(|t| t.to_timespec())
.unwrap_or(TIMESPEC_MAX);
#[cfg(target_os = "nto")]
let timeout = Timespec::now(libc::CLOCK_MONOTONIC)
.checked_add_duration(&dur)
.and_then(|t| t.to_timespec_capped())
.unwrap_or(TIMESPEC_MAX_CAPPED);
let r = libc::pthread_cond_timedwait(raw(self), mutex, &timeout);
assert!(r == libc::ETIMEDOUT || r == 0);
r == 0
}
// This implementation is modeled after libcxx's condition_variable
// https://github.com/llvm-mirror/libcxx/blob/release_35/src/condition_variable.cpp#L46
// https://github.com/llvm-mirror/libcxx/blob/release_35/include/__mutex_base#L367
#[cfg(any(
target_os = "macos",
target_os = "ios",
target_os = "watchos",
target_os = "android",
target_os = "espidf",
target_os = "horizon"
))]
pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
use crate::sys::time::SystemTime;
use crate::time::Instant;
let mutex = pthread_mutex::raw(mutex);
self.verify(mutex);
// 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, and possible bugs of other OSes, timeout
// is clamped to 1000 years, which is allowable per the API of `wait_timeout`
// because of spurious wakeups.
let dur = Duration::min(dur, Duration::from_secs(1000 * 365 * 86400));
// pthread_cond_timedwait uses system time, but we want to report timeout
// based on stable time.
let now = Instant::now();
let timeout = SystemTime::now()
.t
.checked_add_duration(&dur)
.and_then(|t| t.to_timespec())
.unwrap_or(TIMESPEC_MAX);
let r = libc::pthread_cond_timedwait(raw(self), mutex, &timeout);
debug_assert!(r == libc::ETIMEDOUT || r == 0);
// ETIMEDOUT is not a totally reliable method of determining timeout due
// to clock shifts, so do the check ourselves
now.elapsed() < dur
}
}
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