From 17d40c6057c88f4c432b0d7bac88e1b84cb7e67f Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:03:36 +0200 Subject: Adding upstream version 1.65.0+dfsg1. Signed-off-by: Daniel Baumann --- library/std/src/sys/hermit/rwlock.rs | 144 ----------------------------------- 1 file changed, 144 deletions(-) delete mode 100644 library/std/src/sys/hermit/rwlock.rs (limited to 'library/std/src/sys/hermit/rwlock.rs') diff --git a/library/std/src/sys/hermit/rwlock.rs b/library/std/src/sys/hermit/rwlock.rs deleted file mode 100644 index 9701bab1f..000000000 --- a/library/std/src/sys/hermit/rwlock.rs +++ /dev/null @@ -1,144 +0,0 @@ -use crate::cell::UnsafeCell; -use crate::sys::locks::{MovableCondvar, Mutex}; -use crate::sys_common::lazy_box::{LazyBox, LazyInit}; - -pub struct RwLock { - lock: Mutex, - cond: MovableCondvar, - state: UnsafeCell, -} - -pub type MovableRwLock = RwLock; - -enum State { - Unlocked, - Reading(usize), - Writing, -} - -unsafe impl Send for RwLock {} -unsafe impl Sync for RwLock {} - -// This rwlock implementation is a relatively simple implementation which has a -// condition variable for readers/writers as well as a mutex protecting the -// internal state of the lock. A current downside of the implementation is that -// unlocking the lock will notify *all* waiters rather than just readers or just -// writers. This can cause lots of "thundering stampede" problems. While -// hopefully correct this implementation is very likely to want to be changed in -// the future. - -impl RwLock { - pub const fn new() -> RwLock { - RwLock { - lock: Mutex::new(), - cond: MovableCondvar::new(), - state: UnsafeCell::new(State::Unlocked), - } - } - - #[inline] - pub unsafe fn read(&self) { - self.lock.lock(); - while !(*self.state.get()).inc_readers() { - self.cond.wait(&self.lock); - } - self.lock.unlock(); - } - - #[inline] - pub unsafe fn try_read(&self) -> bool { - self.lock.lock(); - let ok = (*self.state.get()).inc_readers(); - self.lock.unlock(); - return ok; - } - - #[inline] - pub unsafe fn write(&self) { - self.lock.lock(); - while !(*self.state.get()).inc_writers() { - self.cond.wait(&self.lock); - } - self.lock.unlock(); - } - - #[inline] - pub unsafe fn try_write(&self) -> bool { - self.lock.lock(); - let ok = (*self.state.get()).inc_writers(); - self.lock.unlock(); - return ok; - } - - #[inline] - pub unsafe fn read_unlock(&self) { - self.lock.lock(); - let notify = (*self.state.get()).dec_readers(); - self.lock.unlock(); - if notify { - // FIXME: should only wake up one of these some of the time - self.cond.notify_all(); - } - } - - #[inline] - pub unsafe fn write_unlock(&self) { - self.lock.lock(); - (*self.state.get()).dec_writers(); - self.lock.unlock(); - // FIXME: should only wake up one of these some of the time - self.cond.notify_all(); - } -} - -impl State { - fn inc_readers(&mut self) -> bool { - match *self { - State::Unlocked => { - *self = State::Reading(1); - true - } - State::Reading(ref mut cnt) => { - *cnt += 1; - true - } - State::Writing => false, - } - } - - fn inc_writers(&mut self) -> bool { - match *self { - State::Unlocked => { - *self = State::Writing; - true - } - State::Reading(_) | State::Writing => false, - } - } - - fn dec_readers(&mut self) -> bool { - let zero = match *self { - State::Reading(ref mut cnt) => { - *cnt -= 1; - *cnt == 0 - } - State::Unlocked | State::Writing => invalid(), - }; - if zero { - *self = State::Unlocked; - } - zero - } - - fn dec_writers(&mut self) { - match *self { - State::Writing => {} - State::Unlocked | State::Reading(_) => invalid(), - } - *self = State::Unlocked; - } -} - -fn invalid() -> ! { - panic!("inconsistent rwlock"); -} -- cgit v1.2.3