diff options
Diffstat (limited to 'library')
| -rw-r--r-- | library/std/src/sync/mpmc/array.rs | 14 | ||||
| -rw-r--r-- | library/std/src/sync/mpmc/list.rs | 16 | ||||
| -rw-r--r-- | library/std/src/sync/mpmc/mod.rs | 2 | ||||
| -rw-r--r-- | library/std/src/sync/mpmc/utils.rs | 31 | ||||
| -rw-r--r-- | library/std/src/sync/mpmc/zero.rs | 2 | ||||
| -rw-r--r-- | library/std/src/sync/mpsc/mod.rs | 9 | ||||
| -rw-r--r-- | library/std/src/sync/mpsc/sync_tests.rs | 8 |
7 files changed, 49 insertions, 33 deletions
diff --git a/library/std/src/sync/mpmc/array.rs b/library/std/src/sync/mpmc/array.rs index f71edc6c525..c1e3e48b044 100644 --- a/library/std/src/sync/mpmc/array.rs +++ b/library/std/src/sync/mpmc/array.rs @@ -168,7 +168,7 @@ impl<T> Channel<T> { return true; } Err(_) => { - backoff.spin(); + backoff.spin_light(); tail = self.tail.load(Ordering::Relaxed); } } @@ -182,11 +182,11 @@ impl<T> Channel<T> { return false; } - backoff.spin(); + backoff.spin_light(); tail = self.tail.load(Ordering::Relaxed); } else { // Snooze because we need to wait for the stamp to get updated. - backoff.snooze(); + backoff.spin_heavy(); tail = self.tail.load(Ordering::Relaxed); } } @@ -251,7 +251,7 @@ impl<T> Channel<T> { return true; } Err(_) => { - backoff.spin(); + backoff.spin_light(); head = self.head.load(Ordering::Relaxed); } } @@ -273,11 +273,11 @@ impl<T> Channel<T> { } } - backoff.spin(); + backoff.spin_light(); head = self.head.load(Ordering::Relaxed); } else { // Snooze because we need to wait for the stamp to get updated. - backoff.snooze(); + backoff.spin_heavy(); head = self.head.load(Ordering::Relaxed); } } @@ -330,7 +330,7 @@ impl<T> Channel<T> { if backoff.is_completed() { break; } else { - backoff.spin(); + backoff.spin_light(); } } diff --git a/library/std/src/sync/mpmc/list.rs b/library/std/src/sync/mpmc/list.rs index 2d5b2fb3b23..ec6c0726ac7 100644 --- a/library/std/src/sync/mpmc/list.rs +++ b/library/std/src/sync/mpmc/list.rs @@ -46,7 +46,7 @@ impl<T> Slot<T> { fn wait_write(&self) { let backoff = Backoff::new(); while self.state.load(Ordering::Acquire) & WRITE == 0 { - backoff.snooze(); + backoff.spin_heavy(); } } } @@ -82,7 +82,7 @@ impl<T> Block<T> { if !next.is_null() { return next; } - backoff.snooze(); + backoff.spin_heavy(); } } @@ -191,7 +191,7 @@ impl<T> Channel<T> { // If we reached the end of the block, wait until the next one is installed. if offset == BLOCK_CAP { - backoff.snooze(); + backoff.spin_heavy(); tail = self.tail.index.load(Ordering::Acquire); block = self.tail.block.load(Ordering::Acquire); continue; @@ -247,7 +247,7 @@ impl<T> Channel<T> { return true; }, Err(_) => { - backoff.spin(); + backoff.spin_light(); tail = self.tail.index.load(Ordering::Acquire); block = self.tail.block.load(Ordering::Acquire); } @@ -286,7 +286,7 @@ impl<T> Channel<T> { // If we reached the end of the block, wait until the next one is installed. if offset == BLOCK_CAP { - backoff.snooze(); + backoff.spin_heavy(); head = self.head.index.load(Ordering::Acquire); block = self.head.block.load(Ordering::Acquire); continue; @@ -320,7 +320,7 @@ impl<T> Channel<T> { // The block can be null here only if the first message is being sent into the channel. // In that case, just wait until it gets initialized. if block.is_null() { - backoff.snooze(); + backoff.spin_heavy(); head = self.head.index.load(Ordering::Acquire); block = self.head.block.load(Ordering::Acquire); continue; @@ -351,7 +351,7 @@ impl<T> Channel<T> { return true; }, Err(_) => { - backoff.spin(); + backoff.spin_light(); head = self.head.index.load(Ordering::Acquire); block = self.head.block.load(Ordering::Acquire); } @@ -542,7 +542,7 @@ impl<T> Channel<T> { // New updates to tail will be rejected by MARK_BIT and aborted unless it's // at boundary. We need to wait for the updates take affect otherwise there // can be memory leaks. - backoff.snooze(); + backoff.spin_heavy(); tail = self.tail.index.load(Ordering::Acquire); } diff --git a/library/std/src/sync/mpmc/mod.rs b/library/std/src/sync/mpmc/mod.rs index cef99c58843..7a602cecd3b 100644 --- a/library/std/src/sync/mpmc/mod.rs +++ b/library/std/src/sync/mpmc/mod.rs @@ -43,7 +43,7 @@ mod zero; use crate::fmt; use crate::panic::{RefUnwindSafe, UnwindSafe}; use crate::time::{Duration, Instant}; -use error::*; +pub use error::*; /// Creates a channel of unbounded capacity. /// diff --git a/library/std/src/sync/mpmc/utils.rs b/library/std/src/sync/mpmc/utils.rs index e030c55ce8f..cfe42750d52 100644 --- a/library/std/src/sync/mpmc/utils.rs +++ b/library/std/src/sync/mpmc/utils.rs @@ -91,9 +91,8 @@ impl<T> DerefMut for CachePadded<T> { } const SPIN_LIMIT: u32 = 6; -const YIELD_LIMIT: u32 = 10; -/// Performs exponential backoff in spin loops. +/// Performs quadratic backoff in spin loops. pub struct Backoff { step: Cell<u32>, } @@ -104,25 +103,27 @@ impl Backoff { Backoff { step: Cell::new(0) } } - /// Backs off in a lock-free loop. + /// Backs off using lightweight spinning. /// - /// This method should be used when we need to retry an operation because another thread made - /// progress. + /// This method should be used for: + /// - Retrying an operation because another thread made progress. i.e. on CAS failure. + /// - Waiting for an operation to complete by spinning optimistically for a few iterations + /// before falling back to parking the thread (see `Backoff::is_completed`). #[inline] - pub fn spin(&self) { + pub fn spin_light(&self) { let step = self.step.get().min(SPIN_LIMIT); for _ in 0..step.pow(2) { crate::hint::spin_loop(); } - if self.step.get() <= SPIN_LIMIT { - self.step.set(self.step.get() + 1); - } + self.step.set(self.step.get() + 1); } - /// Backs off in a blocking loop. + /// Backs off using heavyweight spinning. + /// + /// This method should be used in blocking loops where parking the thread is not an option. #[inline] - pub fn snooze(&self) { + pub fn spin_heavy(&self) { if self.step.get() <= SPIN_LIMIT { for _ in 0..self.step.get().pow(2) { crate::hint::spin_loop() @@ -131,14 +132,12 @@ impl Backoff { crate::thread::yield_now(); } - if self.step.get() <= YIELD_LIMIT { - self.step.set(self.step.get() + 1); - } + self.step.set(self.step.get() + 1); } - /// Returns `true` if quadratic backoff has completed and blocking the thread is advised. + /// Returns `true` if quadratic backoff has completed and parking the thread is advised. #[inline] pub fn is_completed(&self) -> bool { - self.step.get() > YIELD_LIMIT + self.step.get() > SPIN_LIMIT } } diff --git a/library/std/src/sync/mpmc/zero.rs b/library/std/src/sync/mpmc/zero.rs index fccd6c29a7e..33f768dcbe9 100644 --- a/library/std/src/sync/mpmc/zero.rs +++ b/library/std/src/sync/mpmc/zero.rs @@ -57,7 +57,7 @@ impl<T> Packet<T> { fn wait_ready(&self) { let backoff = Backoff::new(); while !self.ready.load(Ordering::Acquire) { - backoff.snooze(); + backoff.spin_heavy(); } } } diff --git a/library/std/src/sync/mpsc/mod.rs b/library/std/src/sync/mpsc/mod.rs index adb488d4378..6e3c28f10bb 100644 --- a/library/std/src/sync/mpsc/mod.rs +++ b/library/std/src/sync/mpsc/mod.rs @@ -738,6 +738,15 @@ impl<T> SyncSender<T> { pub fn try_send(&self, t: T) -> Result<(), TrySendError<T>> { self.inner.try_send(t) } + + // Attempts to send for a value on this receiver, returning an error if the + // corresponding channel has hung up, or if it waits more than `timeout`. + // + // This method is currently private and only used for tests. + #[allow(unused)] + fn send_timeout(&self, t: T, timeout: Duration) -> Result<(), mpmc::SendTimeoutError<T>> { + self.inner.send_timeout(t, timeout) + } } #[stable(feature = "rust1", since = "1.0.0")] diff --git a/library/std/src/sync/mpsc/sync_tests.rs b/library/std/src/sync/mpsc/sync_tests.rs index 63c79436974..9d2f92ffc9b 100644 --- a/library/std/src/sync/mpsc/sync_tests.rs +++ b/library/std/src/sync/mpsc/sync_tests.rs @@ -1,5 +1,6 @@ use super::*; use crate::env; +use crate::sync::mpmc::SendTimeoutError; use crate::thread; use crate::time::Duration; @@ -42,6 +43,13 @@ fn recv_timeout() { } #[test] +fn send_timeout() { + let (tx, _rx) = sync_channel::<i32>(1); + assert_eq!(tx.send_timeout(1, Duration::from_millis(1)), Ok(())); + assert_eq!(tx.send_timeout(1, Duration::from_millis(1)), Err(SendTimeoutError::Timeout(1))); +} + +#[test] fn smoke_threads() { let (tx, rx) = sync_channel::<i32>(0); let _t = thread::spawn(move || { |