Merge #855 #858

bors[bot] · RalfJung · taiki-e · web-flow · commit 4b949c2b79d6 · 2022-07-01T03:19:05.000Z
855: Miri: enable preemption again r=taiki-e a=RalfJung Miri has a [work-around](rust-lang/miri#2248) for rust-lang/rust#55005 now. Also, "check-number-validity" is on by default these days. And I am not sure why "compare-exchange-weak-failure-rate=0.0" was set so let's see what happens when we remove it. :) 858: Ignore clippy::let_unit_value lint r=taiki-e a=taiki-e Co-authored-by: Ralf Jung <post@ralfj.de> Co-authored-by: Taiki Endo <te316e89@gmail.com>
diff --git a/ci/miri.sh b/ci/miri.sh
@@ -3,37 +3,40 @@ set -euxo pipefail
 IFS=$'\n\t'
 cd "$(dirname "$0")"/..
 
+# We need 'ts' for the per-line timing
+sudo apt-get -y install moreutils
+echo
+
 export RUSTFLAGS="${RUSTFLAGS:-} -Z randomize-layout"
 
-# disable preemption due to https://github.com/rust-lang/rust/issues/55005
-MIRIFLAGS="-Zmiri-strict-provenance -Zmiri-symbolic-alignment-check -Zmiri-disable-isolation -Zmiri-preemption-rate=0" \
+# -Zmiri-ignore-leaks is needed because we use detached threads in tests/docs: https://github.com/rust-lang/miri/issues/1371
+MIRIFLAGS="-Zmiri-symbolic-alignment-check -Zmiri-disable-isolation -Zmiri-ignore-leaks" \
     cargo miri test \
     -p crossbeam-queue \
-    -p crossbeam-utils
+    -p crossbeam-utils 2>&1 | ts -i '%.s  '
 
 # -Zmiri-ignore-leaks is needed because we use detached threads in tests/docs: https://github.com/rust-lang/miri/issues/1371
-# disable preemption due to https://github.com/rust-lang/rust/issues/55005
-MIRIFLAGS="-Zmiri-strict-provenance -Zmiri-symbolic-alignment-check -Zmiri-disable-isolation -Zmiri-ignore-leaks -Zmiri-preemption-rate=0" \
+MIRIFLAGS="-Zmiri-symbolic-alignment-check -Zmiri-disable-isolation -Zmiri-ignore-leaks" \
     cargo miri test \
-    -p crossbeam-channel
+    -p crossbeam-channel 2>&1 | ts -i '%.s  '
 
 # -Zmiri-ignore-leaks is needed for https://github.com/crossbeam-rs/crossbeam/issues/579
 # -Zmiri-disable-stacked-borrows is needed for https://github.com/crossbeam-rs/crossbeam/issues/545
-# disable preemption due to https://github.com/rust-lang/rust/issues/55005
-MIRIFLAGS="-Zmiri-check-number-validity -Zmiri-symbolic-alignment-check -Zmiri-disable-isolation -Zmiri-disable-stacked-borrows -Zmiri-ignore-leaks -Zmiri-preemption-rate=0" \
+MIRIFLAGS="-Zmiri-symbolic-alignment-check -Zmiri-disable-isolation -Zmiri-disable-stacked-borrows -Zmiri-ignore-leaks" \
     cargo miri test \
     -p crossbeam-epoch \
-    -p crossbeam-skiplist
+    -p crossbeam-skiplist 2>&1 | ts -i '%.s  '
 
 # -Zmiri-ignore-leaks is needed for https://github.com/crossbeam-rs/crossbeam/issues/579
 # -Zmiri-disable-stacked-borrows is needed for https://github.com/crossbeam-rs/crossbeam/issues/545
-# disable preemption due to https://github.com/rust-lang/rust/issues/55005
-MIRIFLAGS="-Zmiri-check-number-validity -Zmiri-symbolic-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-ignore-leaks -Zmiri-compare-exchange-weak-failure-rate=0.0 -Zmiri-preemption-rate=0" \
+# -Zmiri-compare-exchange-weak-failure-rate=0.0 is needed because some sequential tests (e.g.,
+# doctest of Stealer::steal) incorrectly assume that sequential weak CAS will never fail.
+# -Zmiri-preemption-rate=0 is needed because this code technically has UB and Miri catches that.
+MIRIFLAGS="-Zmiri-symbolic-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-ignore-leaks -Zmiri-compare-exchange-weak-failure-rate=0.0 -Zmiri-preemption-rate=0" \
     cargo miri test \
-    -p crossbeam-deque
+    -p crossbeam-deque 2>&1 | ts -i '%.s  '
 
 # -Zmiri-ignore-leaks is needed for https://github.com/crossbeam-rs/crossbeam/issues/579
-# disable preemption due to https://github.com/rust-lang/rust/issues/55005
-MIRIFLAGS="-Zmiri-check-number-validity -Zmiri-symbolic-alignment-check -Zmiri-ignore-leaks -Zmiri-preemption-rate=0" \
+MIRIFLAGS="-Zmiri-symbolic-alignment-check -Zmiri-ignore-leaks" \
     cargo miri test \
-    -p crossbeam
+    -p crossbeam 2>&1 | ts -i '%.s  '
diff --git a/crossbeam-channel/tests/array.rs b/crossbeam-channel/tests/array.rs
@@ -377,7 +377,7 @@ fn spsc() {
 #[test]
 fn mpmc() {
     #[cfg(miri)]
-    const COUNT: usize = 100;
+    const COUNT: usize = 50;
     #[cfg(not(miri))]
     const COUNT: usize = 25_000;
     const THREADS: usize = 4;
@@ -532,16 +532,12 @@ fn drops() {
             scope.spawn(|_| {
                 for _ in 0..steps {
                     r.recv().unwrap();
-                    #[cfg(miri)]
-                    std::thread::yield_now(); // https://github.com/rust-lang/miri/issues/1388
                 }
             });
 
             scope.spawn(|_| {
                 for _ in 0..steps {
                     s.send(DropCounter).unwrap();
-                    #[cfg(miri)]
-                    std::thread::yield_now(); // https://github.com/rust-lang/miri/issues/1388
                 }
             });
         })
diff --git a/crossbeam-channel/tests/golang.rs b/crossbeam-channel/tests/golang.rs
@@ -959,7 +959,7 @@ mod chan_test {
     #[test]
     fn test_chan() {
         #[cfg(miri)]
-        const N: i32 = 20;
+        const N: i32 = 12;
         #[cfg(not(miri))]
         const N: i32 = 200;
 
@@ -1489,7 +1489,7 @@ mod chan_test {
     fn test_multi_consumer() {
         const NWORK: usize = 23;
         #[cfg(miri)]
-        const NITER: usize = 100;
+        const NITER: usize = 50;
         #[cfg(not(miri))]
         const NITER: usize = 271828;
 
diff --git a/crossbeam-channel/tests/list.rs b/crossbeam-channel/tests/list.rs
@@ -433,8 +433,6 @@ fn drops() {
             scope.spawn(|_| {
                 for _ in 0..steps {
                     r.recv().unwrap();
-                    #[cfg(miri)]
-                    std::thread::yield_now(); // https://github.com/rust-lang/miri/issues/1388
                 }
             });
 
diff --git a/crossbeam-channel/tests/mpsc.rs b/crossbeam-channel/tests/mpsc.rs
@@ -339,25 +339,22 @@ mod channel_tests {
 
     #[test]
     fn stress_shared() {
-        #[cfg(miri)]
-        const AMT: u32 = 100;
-        #[cfg(not(miri))]
-        const AMT: u32 = 10000;
-        const NTHREADS: u32 = 8;
+        let amt: u32 = if cfg!(miri) { 100 } else { 10_000 };
+        let nthreads: u32 = if cfg!(miri) { 4 } else { 8 };
         let (tx, rx) = channel::<i32>();
 
         let t = thread::spawn(move || {
-            for _ in 0..AMT * NTHREADS {
+            for _ in 0..amt * nthreads {
                 assert_eq!(rx.recv().unwrap(), 1);
             }
             assert!(rx.try_recv().is_err());
         });
 
-        let mut ts = Vec::with_capacity(NTHREADS as usize);
-        for _ in 0..NTHREADS {
+        let mut ts = Vec::with_capacity(nthreads as usize);
+        for _ in 0..nthreads {
             let tx = tx.clone();
             let t = thread::spawn(move || {
-                for _ in 0..AMT {
+                for _ in 0..amt {
                     tx.send(1).unwrap();
                 }
             });
diff --git a/crossbeam-channel/tests/thread_locals.rs b/crossbeam-channel/tests/thread_locals.rs
@@ -1,6 +1,6 @@
 //! Tests that make sure accessing thread-locals while exiting the thread doesn't cause panics.
 
-#![cfg(not(miri))] // error: abnormal termination: the evaluated program aborted execution
+#![cfg(not(miri))] // Miri detects that this test is buggy: the destructor of `FOO` uses `std::thread::current()`!
 
 use std::thread;
 use std::time::Duration;
diff --git a/crossbeam-channel/tests/zero.rs b/crossbeam-channel/tests/zero.rs
@@ -403,7 +403,7 @@ fn drops() {
     #[cfg(not(miri))]
     const RUNS: usize = 100;
     #[cfg(miri)]
-    const STEPS: usize = 500;
+    const STEPS: usize = 100;
     #[cfg(not(miri))]
     const STEPS: usize = 10_000;
 
diff --git a/crossbeam-deque/src/deque.rs b/crossbeam-deque/src/deque.rs
@@ -53,6 +53,8 @@ impl<T> Buffer<T> {
     /// Returns a pointer to the task at the specified `index`.
     unsafe fn at(&self, index: isize) -> *mut T {
         // `self.cap` is always a power of two.
+        // We do all the loads at `MaybeUninit` because we might realize, after loading, that we
+        // don't actually have the right to access this memory.
         self.ptr.offset(index & (self.cap - 1) as isize)
     }
 
@@ -62,18 +64,18 @@ impl<T> Buffer<T> {
     /// technically speaking a data race and therefore UB. We should use an atomic store here, but
     /// that would be more expensive and difficult to implement generically for all types `T`.
     /// Hence, as a hack, we use a volatile write instead.
-    unsafe fn write(&self, index: isize, task: T) {
-        ptr::write_volatile(self.at(index), task)
+    unsafe fn write(&self, index: isize, task: MaybeUninit<T>) {
+        ptr::write_volatile(self.at(index) as *mut MaybeUninit<T>, task)
     }
 
     /// Reads a task from the specified `index`.
     ///
     /// This method might be concurrently called with another `write` at the same index, which is
     /// technically speaking a data race and therefore UB. We should use an atomic load here, but
     /// that would be more expensive and difficult to implement generically for all types `T`.
-    /// Hence, as a hack, we use a volatile write instead.
-    unsafe fn read(&self, index: isize) -> T {
-        ptr::read_volatile(self.at(index))
+    /// Hence, as a hack, we use a volatile load instead.
+    unsafe fn read(&self, index: isize) -> MaybeUninit<T> {
+        ptr::read_volatile(self.at(index) as *mut MaybeUninit<T>)
     }
 }
 
@@ -406,7 +408,7 @@ impl<T> Worker<T> {
 
         // Write `task` into the slot.
         unsafe {
-            buffer.write(b, task);
+            buffer.write(b, MaybeUninit::new(task));
         }
 
         atomic::fence(Ordering::Release);
@@ -461,7 +463,7 @@ impl<T> Worker<T> {
                 unsafe {
                     // Read the popped task.
                     let buffer = self.buffer.get();
-                    let task = buffer.read(f);
+                    let task = buffer.read(f).assume_init();
 
                     // Shrink the buffer if `len - 1` is less than one fourth of the capacity.
                     if buffer.cap > MIN_CAP && len <= buffer.cap as isize / 4 {
@@ -509,8 +511,8 @@ impl<T> Worker<T> {
                             )
                             .is_err()
                         {
-                            // Failed. We didn't pop anything.
-                            mem::forget(task.take());
+                            // Failed. We didn't pop anything. Reset to `None`.
+                            task.take();
                         }
 
                         // Restore the back index to the original task.
@@ -524,7 +526,7 @@ impl<T> Worker<T> {
                         }
                     }
 
-                    task
+                    task.map(|t| unsafe { t.assume_init() })
                 }
             }
         }
@@ -661,12 +663,11 @@ impl<T> Stealer<T> {
                 .is_err()
         {
             // We didn't steal this task, forget it.
-            mem::forget(task);
             return Steal::Retry;
         }
 
         // Return the stolen task.
-        Steal::Success(task)
+        Steal::Success(unsafe { task.assume_init() })
     }
 
     /// Steals a batch of tasks and pushes them into another worker.
@@ -821,7 +822,6 @@ impl<T> Stealer<T> {
                             .is_err()
                     {
                         // We didn't steal this task, forget it and break from the loop.
-                        mem::forget(task);
                         batch_size = i;
                         break;
                     }
@@ -975,7 +975,6 @@ impl<T> Stealer<T> {
                         .is_err()
                 {
                     // We didn't steal this task, forget it.
-                    mem::forget(task);
                     return Steal::Retry;
                 }
 
@@ -992,7 +991,6 @@ impl<T> Stealer<T> {
                     .is_err()
                 {
                     // We didn't steal this task, forget it.
-                    mem::forget(task);
                     return Steal::Retry;
                 }
 
@@ -1037,7 +1035,6 @@ impl<T> Stealer<T> {
                             .is_err()
                     {
                         // We didn't steal this task, forget it and break from the loop.
-                        mem::forget(tmp);
                         batch_size = i;
                         break;
                     }
@@ -1077,7 +1074,7 @@ impl<T> Stealer<T> {
         dest.inner.back.store(dest_b, Ordering::Release);
 
         // Return with success.
-        Steal::Success(task)
+        Steal::Success(unsafe { task.assume_init() })
     }
 }
 
@@ -1535,7 +1532,7 @@ impl<T> Injector<T> {
                         // Read the task.
                         let slot = (*block).slots.get_unchecked(offset + i);
                         slot.wait_write();
-                        let task = slot.task.get().read().assume_init();
+                        let task = slot.task.get().read();
 
                         // Write it into the destination queue.
                         dest_buffer.write(dest_b.wrapping_add(i as isize), task);
@@ -1547,7 +1544,7 @@ impl<T> Injector<T> {
                         // Read the task.
                         let slot = (*block).slots.get_unchecked(offset + i);
                         slot.wait_write();
-                        let task = slot.task.get().read().assume_init();
+                        let task = slot.task.get().read();
 
                         // Write it into the destination queue.
                         dest_buffer.write(dest_b.wrapping_add((batch_size - 1 - i) as isize), task);
@@ -1689,7 +1686,7 @@ impl<T> Injector<T> {
             // Read the task.
             let slot = (*block).slots.get_unchecked(offset);
             slot.wait_write();
-            let task = slot.task.get().read().assume_init();
+            let task = slot.task.get().read();
 
             match dest.flavor {
                 Flavor::Fifo => {
@@ -1698,7 +1695,7 @@ impl<T> Injector<T> {
                         // Read the task.
                         let slot = (*block).slots.get_unchecked(offset + i + 1);
                         slot.wait_write();
-                        let task = slot.task.get().read().assume_init();
+                        let task = slot.task.get().read();
 
                         // Write it into the destination queue.
                         dest_buffer.write(dest_b.wrapping_add(i as isize), task);
@@ -1711,7 +1708,7 @@ impl<T> Injector<T> {
                         // Read the task.
                         let slot = (*block).slots.get_unchecked(offset + i + 1);
                         slot.wait_write();
-                        let task = slot.task.get().read().assume_init();
+                        let task = slot.task.get().read();
 
                         // Write it into the destination queue.
                         dest_buffer.write(dest_b.wrapping_add((batch_size - 1 - i) as isize), task);
@@ -1744,7 +1741,7 @@ impl<T> Injector<T> {
                 }
             }
 
-            Steal::Success(task)
+            Steal::Success(task.assume_init())
         }
     }
 
diff --git a/crossbeam-queue/tests/array_queue.rs b/crossbeam-queue/tests/array_queue.rs
diff --git a/crossbeam-queue/tests/seg_queue.rs b/crossbeam-queue/tests/seg_queue.rs
diff --git a/crossbeam-utils/src/atomic/atomic_cell.rs b/crossbeam-utils/src/atomic/atomic_cell.rs
diff --git a/crossbeam-utils/tests/wait_group.rs b/crossbeam-utils/tests/wait_group.rs

Original file line number	Diff line number	Diff line change
`@@ -433,8 +433,6 @@ fn drops() {`
`433`	`433`	`scope.spawn(\|_\| {`
`434`	`434`	`for _ in 0..steps {`
`435`	`435`	`r.recv().unwrap();`
`436`		`- #[cfg(miri)]`
`437`		`- std::thread::yield_now(); // https://github.com/rust-lang/miri/issues/1388`
`438`	`436`	`}`
`439`	`437`	`});`
`440`	`438`
Original file line number	Diff line number	Diff line change
`@@ -53,6 +53,8 @@ impl<T> Buffer<T> {`
`53`	`53`	/// Returns a pointer to the task at the specified `index`.
`54`	`54`	`unsafe fn at(&self, index: isize) -> *mut T {`
`55`	`55`	// `self.cap` is always a power of two.
	`56`	+ // We do all the loads at `MaybeUninit` because we might realize, after loading, that we
	`57`	`+ // don't actually have the right to access this memory.`
`56`	`58`	`self.ptr.offset(index & (self.cap - 1) as isize)`
`57`	`59`	`}`
`58`	`60`
`@@ -62,18 +64,18 @@ impl<T> Buffer<T> {`
`62`	`64`	`/// technically speaking a data race and therefore UB. We should use an atomic store here, but`
`63`	`65`	/// that would be more expensive and difficult to implement generically for all types `T`.
`64`	`66`	`/// Hence, as a hack, we use a volatile write instead.`
`65`		`- unsafe fn write(&self, index: isize, task: T) {`
`66`		`- ptr::write_volatile(self.at(index), task)`
	`67`	`+ unsafe fn write(&self, index: isize, task: MaybeUninit<T>) {`
	`68`	`+ ptr::write_volatile(self.at(index) as *mut MaybeUninit<T>, task)`
`67`	`69`	`}`
`68`	`70`
`69`	`71`	/// Reads a task from the specified `index`.
`70`	`72`	`///`
`71`	`73`	/// This method might be concurrently called with another `write` at the same index, which is
`72`	`74`	`/// technically speaking a data race and therefore UB. We should use an atomic load here, but`
`73`	`75`	/// that would be more expensive and difficult to implement generically for all types `T`.
`74`		`- /// Hence, as a hack, we use a volatile write instead.`
`75`		`- unsafe fn read(&self, index: isize) -> T {`
`76`		`- ptr::read_volatile(self.at(index))`
	`76`	`+ /// Hence, as a hack, we use a volatile load instead.`
	`77`	`+ unsafe fn read(&self, index: isize) -> MaybeUninit<T> {`
	`78`	`+ ptr::read_volatile(self.at(index) as *mut MaybeUninit<T>)`
`77`	`79`	`}`
`78`	`80`	`}`
`79`	`81`
`@@ -406,7 +408,7 @@ impl<T> Worker<T> {`
`406`	`408`
`407`	`409`	// Write `task` into the slot.
`408`	`410`	`unsafe {`
`409`		`- buffer.write(b, task);`
	`411`	`+ buffer.write(b, MaybeUninit::new(task));`
`410`	`412`	`}`
`411`	`413`
`412`	`414`	`atomic::fence(Ordering::Release);`
`@@ -461,7 +463,7 @@ impl<T> Worker<T> {`
`461`	`463`	`unsafe {`
`462`	`464`	`// Read the popped task.`
`463`	`465`	`let buffer = self.buffer.get();`
`464`		`- let task = buffer.read(f);`
	`466`	`+ let task = buffer.read(f).assume_init();`
`465`	`467`
`466`	`468`	// Shrink the buffer if `len - 1` is less than one fourth of the capacity.
`467`	`469`	`if buffer.cap > MIN_CAP && len <= buffer.cap as isize / 4 {`
`@@ -509,8 +511,8 @@ impl<T> Worker<T> {`
`509`	`511`	`)`
`510`	`512`	`.is_err()`
`511`	`513`	`{`
`512`		`- // Failed. We didn't pop anything.`
`513`		`- mem::forget(task.take());`
	`514`	+ // Failed. We didn't pop anything. Reset to `None`.
	`515`	`+ task.take();`
`514`	`516`	`}`
`515`	`517`
`516`	`518`	`// Restore the back index to the original task.`
`@@ -524,7 +526,7 @@ impl<T> Worker<T> {`
`524`	`526`	`}`
`525`	`527`	`}`
`526`	`528`
`527`		`- task`
	`529`	`+ task.map(\|t\| unsafe { t.assume_init() })`
`528`	`530`	`}`
`529`	`531`	`}`
`530`	`532`	`}`
`@@ -661,12 +663,11 @@ impl<T> Stealer<T> {`
`661`	`663`	`.is_err()`
`662`	`664`	`{`
`663`	`665`	`// We didn't steal this task, forget it.`
`664`		`- mem::forget(task);`
`665`	`666`	`return Steal::Retry;`
`666`	`667`	`}`
`667`	`668`
`668`	`669`	`// Return the stolen task.`
`669`		`- Steal::Success(task)`
	`670`	`+ Steal::Success(unsafe { task.assume_init() })`
`670`	`671`	`}`
`671`	`672`
`672`	`673`	`/// Steals a batch of tasks and pushes them into another worker.`
`@@ -821,7 +822,6 @@ impl<T> Stealer<T> {`
`821`	`822`	`.is_err()`
`822`	`823`	`{`
`823`	`824`	`// We didn't steal this task, forget it and break from the loop.`
`824`		`- mem::forget(task);`
`825`	`825`	`batch_size = i;`
`826`	`826`	`break;`
`827`	`827`	`}`
`@@ -975,7 +975,6 @@ impl<T> Stealer<T> {`
`975`	`975`	`.is_err()`
`976`	`976`	`{`
`977`	`977`	`// We didn't steal this task, forget it.`
`978`		`- mem::forget(task);`
`979`	`978`	`return Steal::Retry;`
`980`	`979`	`}`
`981`	`980`
`@@ -992,7 +991,6 @@ impl<T> Stealer<T> {`
`992`	`991`	`.is_err()`
`993`	`992`	`{`
`994`	`993`	`// We didn't steal this task, forget it.`
`995`		`- mem::forget(task);`
`996`	`994`	`return Steal::Retry;`
`997`	`995`	`}`
`998`	`996`
`@@ -1037,7 +1035,6 @@ impl<T> Stealer<T> {`
`1037`	`1035`	`.is_err()`
`1038`	`1036`	`{`
`1039`	`1037`	`// We didn't steal this task, forget it and break from the loop.`
`1040`		`- mem::forget(tmp);`
`1041`	`1038`	`batch_size = i;`
`1042`	`1039`	`break;`
`1043`	`1040`	`}`
`@@ -1077,7 +1074,7 @@ impl<T> Stealer<T> {`
`1077`	`1074`	`dest.inner.back.store(dest_b, Ordering::Release);`
`1078`	`1075`
`1079`	`1076`	`// Return with success.`
`1080`		`- Steal::Success(task)`
	`1077`	`+ Steal::Success(unsafe { task.assume_init() })`
`1081`	`1078`	`}`
`1082`	`1079`	`}`
`1083`	`1080`
`@@ -1535,7 +1532,7 @@ impl<T> Injector<T> {`
`1535`	`1532`	`// Read the task.`
`1536`	`1533`	`let slot = (*block).slots.get_unchecked(offset + i);`
`1537`	`1534`	`slot.wait_write();`
`1538`		`- let task = slot.task.get().read().assume_init();`
	`1535`	`+ let task = slot.task.get().read();`
`1539`	`1536`
`1540`	`1537`	`// Write it into the destination queue.`
`1541`	`1538`	`dest_buffer.write(dest_b.wrapping_add(i as isize), task);`
`@@ -1547,7 +1544,7 @@ impl<T> Injector<T> {`
`1547`	`1544`	`// Read the task.`
`1548`	`1545`	`let slot = (*block).slots.get_unchecked(offset + i);`
`1549`	`1546`	`slot.wait_write();`
`1550`		`- let task = slot.task.get().read().assume_init();`
	`1547`	`+ let task = slot.task.get().read();`
`1551`	`1548`
`1552`	`1549`	`// Write it into the destination queue.`
`1553`	`1550`	`dest_buffer.write(dest_b.wrapping_add((batch_size - 1 - i) as isize), task);`
`@@ -1689,7 +1686,7 @@ impl<T> Injector<T> {`
`1689`	`1686`	`// Read the task.`
`1690`	`1687`	`let slot = (*block).slots.get_unchecked(offset);`
`1691`	`1688`	`slot.wait_write();`
`1692`		`- let task = slot.task.get().read().assume_init();`
	`1689`	`+ let task = slot.task.get().read();`
`1693`	`1690`
`1694`	`1691`	`match dest.flavor {`
`1695`	`1692`	`Flavor::Fifo => {`
`@@ -1698,7 +1695,7 @@ impl<T> Injector<T> {`
`1698`	`1695`	`// Read the task.`
`1699`	`1696`	`let slot = (*block).slots.get_unchecked(offset + i + 1);`
`1700`	`1697`	`slot.wait_write();`
`1701`		`- let task = slot.task.get().read().assume_init();`
	`1698`	`+ let task = slot.task.get().read();`
`1702`	`1699`
`1703`	`1700`	`// Write it into the destination queue.`
`1704`	`1701`	`dest_buffer.write(dest_b.wrapping_add(i as isize), task);`
`@@ -1711,7 +1708,7 @@ impl<T> Injector<T> {`
`1711`	`1708`	`// Read the task.`
`1712`	`1709`	`let slot = (*block).slots.get_unchecked(offset + i + 1);`
`1713`	`1710`	`slot.wait_write();`
`1714`		`- let task = slot.task.get().read().assume_init();`
	`1711`	`+ let task = slot.task.get().read();`
`1715`	`1712`
`1716`	`1713`	`// Write it into the destination queue.`
`1717`	`1714`	`dest_buffer.write(dest_b.wrapping_add((batch_size - 1 - i) as isize), task);`
`@@ -1744,7 +1741,7 @@ impl<T> Injector<T> {`
`1744`	`1741`	`}`
`1745`	`1742`	`}`
`1746`	`1743`
`1747`		`- Steal::Success(task)`
	`1744`	`+ Steal::Success(task.assume_init())`
`1748`	`1745`	`}`
`1749`	`1746`	`}`
`1750`	`1747`