Record · corpus.blog/posts/01a08789-803c-7129-942f-6f850cdfa8e0

Never Snooze a Future

jacko.io · published 2 March 2026

A record is what was published and who pointed at it. The text of the post is not held here: read it at the source, or at its Wayback capture.

Read the post at jacko.io Wayback capture

3blogs citing

First cited: 11 Apr 2026
Most recent: 1 May 2026
Rank this month: not ranked
External links: 68
Words captured: 5,661

Cited by

Blog

In the post

Date

qouteall.fun

Rust Async Traps Read at the source ↗

1 May 2026

causality.blog

What Async Promised and What it Delivered Read at the source ↗

21 Apr 2026

samyak.me

Cancellation in async rust Read at the source ↗

11 Apr 2026

Links from this post

Link

Host

https://rust-lang.github.io/wg-async/vision/submitted_stories/status_quo/barbara_battles_buffered_streams.html

rust-lang.github.io

https://rfd.shared.oxide.computer/rfd/0609

rfd.shared.oxide.computer

Cancelling async Rust Read at the source ↗

sunshowers.io

https://play.rust-lang.org/?edition=2024&code=use+futures%3A%3A%7BStreamExt%2C+stream%7D%3B%0Ause+std%3A%3Apin%3A%3Apin%3B%0Ause+tokio%3A%3Async%3A%3AOnceCell%3B%0Ause+tokio%3A%3Atime%3A%3A%7BDuration%2C+timeout%7D%3B%0A%0A%2F%2F%2F+Fetch+some+Zen+wisdom+from+the+GitHub+API.+This+makes+a+network%0A%2F%2F%2F+request+the+first+time+and+caches+the+result.%0Aasync+fn+zen_wisdom%28%29+-%3E+%26%27static+str+%7B%0A++++static+ZEN%3A+OnceCell%3CString%3E+%3D+OnceCell%3A%3Aconst_new%28%29%3B%0A++++ZEN.get_or_init%28async+%7C%7C+%7B%0A++++++++let+url+%3D+%22https%3A%2F%2Fapi.github.com%2Fzen%22%3B%0A++++++++reqwest%3A%3Aget%28url%29.await.unwrap%28%29.text%28%29.await.unwrap%28%29%0A++++%7D%29%0A++++.await%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++%2F%2F+Put+some+Zen+wisdom+in+a+stream.%0A++++let+mut+zen_stream+%3D+pin%21%28stream%3A%3Aonce%28zen_wisdom%28%29%29%29%3B%0A++++%2F%2F+Start+reading+it%2C+but+cancel+the+read+with+a+tight+timeout.%0A++++_+%3D+timeout%28Duration%3A%3Afrom_millis%281%29%2C+zen_stream.next%28%29%29.await%3B%0A++++%2F%2F+Now+the+stream+is+%22snoozed%22%2C+but+it%27s+still+holding+the+%60ZEN%60%0A++++%2F%2F+lock.+Calling+%60zen_wisdom%60+again+is+a+deadlock.%0A++++println%21%28%22We+make+it+here...%22%29%3B%0A++++zen_wisdom%28%29.await%3B%0A++++println%21%28%22...but+not+here.%22%29%3B%0A%7D

play.rust-lang.org

https://docs.rs/tokio/latest/tokio/sync/struct.Mutex.html

docs.rs

https://github.com/oxidecomputer/omicron/issues/9259

github.com

https://github.com/tokio-rs/tokio/blob/0ec0a8546105b9f250f868b77e42c82809703aab/tokio/src/sync/mpsc/bounded.rs

github.com

https://github.com/NationalSecurityAgency/ghidra

github.com

Type 1, 2 and 3 Fun Read at the source ↗

essentialwilderness.com

https://docs.rs/futures/latest/futures/macro.poll.html

docs.rs

https://doc.rust-lang.org/std/future/trait.Future.html

doc.rust-lang.org

https://doc.rust-lang.org/std/sync/struct.Mutex.html

doc.rust-lang.org

https://doc.rust-lang.org/std/process/struct.Child.html

doc.rust-lang.org

https://play.rust-lang.org/?edition=2024&code=use+std%3A%3Apin%3A%3Apin%3B%0Ause+std%3A%3Atask%3A%3APoll%3B%0Ause+std%3A%3Atime%3A%3ADuration%3B%0A%0Astatic+LOCK%3A+tokio%3A%3Async%3A%3AMutex%3C%28%29%3E+%3D+tokio%3A%3Async%3A%3AMutex%3A%3Aconst_new%28%28%29%29%3B%0A%0Aasync+fn+foo%28%29+%7B%0A++++let+_guard+%3D+LOCK.lock%28%29.await%3B%0A++++tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%2810%29%29.await%3B%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++let+mut+future1+%3D+pin%21%28foo%28%29%29%3B%0A++++std%3A%3Afuture%3A%3Apoll_fn%28%7Ccx%7C+%7B%0A++++++++_+%3D+future1.as_mut%28%29.poll%28cx%29%3B%0A++++++++Poll%3A%3AReady%28%28%29%29%0A++++%7D%29%0A++++.await%3B%0A++++println%21%28%22We+make+it+here...%22%29%3B%0A++++foo%28%29.await%3B%0A++++println%21%28%22...but+not+here%21%22%29%3B%0A%7D

play.rust-lang.org

https://play.rust-lang.org/?edition=2024&code=use+std%3A%3Apin%3A%3A%7BPin%2C+pin%7D%3B%0Ause+std%3A%3Atask%3A%3APoll%3B%0Ause+std%3A%3Atime%3A%3ADuration%3B%0A%0Astatic+LOCK%3A+tokio%3A%3Async%3A%3AMutex%3C%28%29%3E+%3D+tokio%3A%3Async%3A%3AMutex%3A%3Aconst_new%28%28%29%29%3B%0A%0Aasync+fn+foo%28%29+%7B%0A++++let+_guard+%3D+LOCK.lock%28%29.await%3B%0A++++tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%2810%29%29.await%3B%0A%7D%0A%0Astruct+PollOnce%3C%27a%2C+Fut%3E%28Pin%3C%26%27a+mut+Fut%3E%29%3B%0A%0Aimpl%3C%27a%2C+Fut%3A+Future%3E+Future+for+PollOnce%3C%27a%2C+Fut%3E+%7B%0A++++type+Output+%3D+%28%29%3B%0A%0A++++fn+poll%28%0A++++++++mut+self%3A+Pin%3C%26mut+Self%3E%2C%0A++++++++cx%3A+%26mut+std%3A%3Atask%3A%3AContext%3C%27_%3E%2C%0A++++%29+-%3E+Poll%3C%28%29%3E+%7B%0A++++++++_+%3D+self.0.as_mut%28%29.poll%28cx%29%3B%0A++++++++Poll%3A%3AReady%28%28%29%29%0A++++%7D%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++let+future1+%3D+pin%21%28foo%28%29%29%3B%0A++++PollOnce%28future1%29.await%3B%0A++++println%21%28%22We+make+it+here...%22%29%3B%0A++++foo%28%29.await%3B%0A++++println%21%28%22...but+not+here%21%22%29%3B%0A%7D

play.rust-lang.org

https://github.com/tokio-rs/tokio/blob/tokio-1.49.0/tokio/src/runtime/park.rs

github.com

https://doc.rust-lang.org/std/task/struct.Waker.html

doc.rust-lang.org

https://docs.rs/tokio/latest/tokio/macro.select.html

docs.rs

https://github.com/oxidecomputer/omicron/pull/9268/changes

github.com

https://play.rust-lang.org/?edition=2024&code=use+std%3A%3Atime%3A%3ADuration%3B%0Ause+tokio%3A%3Aselect%3B%0A%0Astatic+LOCK%3A+tokio%3A%3Async%3A%3AMutex%3C%28%29%3E+%3D+tokio%3A%3Async%3A%3AMutex%3A%3Aconst_new%28%28%29%29%3B%0A%0Aasync+fn+foo%28%29+%7B%0A++++let+_guard+%3D+LOCK.lock%28%29.await%3B%0A++++tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%2810%29%29.await%3B%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++select%21+%7B%0A++++++++_+%3D+foo%28%29+%3D%3E+%7B%7D%0A++++++++_+%3D+tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%285%29%29+%3D%3E+%7B%7D%0A++++%7D%0A++++foo%28%29.await%3B%0A++++println%21%28%0A++++++++%22Passing+the+future+to+%60select%21%60+by+value+fixes+the+deadlock.%22%0A++++%29%3B%0A%7D

play.rust-lang.org

https://docs.rs/tokio/latest/tokio/time/struct.Sleep.html

docs.rs

https://tokio.rs/tokio/tutorial/streams

tokio.rs

https://docs.rs/futures/latest/futures/stream/trait.StreamExt.html

docs.rs

poll_progress Read at the source ↗

without.boats

https://docs.rs/futures/latest/futures/prelude/trait.Stream.html

docs.rs

https://doc.rust-lang.org/std/async_iter/trait.AsyncIterator.html

doc.rust-lang.org

https://docs.rs/futures/latest/futures/stream/trait.Stream.html

docs.rs

https://play.rust-lang.org/?version=nightly&edition=2024&code=%23%21%5Bfeature%28gen_blocks%29%5D%0A%23%21%5Bfeature%28async_iterator%29%5D%0A%0Ause+std%3A%3Aasync_iter%3A%3AAsyncIterator%3B%0Ause+std%3A%3Apin%3A%3A%7BPin%2C+pin%7D%3B%0Ause+tokio%3A%3Async%3A%3Ampsc%3A%3AUnboundedReceiver%3B%0Ause+tokio%3A%3Atime%3A%3A%7BDuration%2C+sleep%7D%3B%0A%0A%2F%2F+a+helper+function+similar+to+%60StreamExt%3A%3Anext%60%0Afn+next%3CT%3E%28%0A++++mut+iter%3A+Pin%3C%26mut+impl+AsyncIterator%3CItem+%3D+T%3E%3E%2C%0A%29+-%3E+impl+Future%3COutput+%3D+Option%3CT%3E%3E+%7B%0A++++futures%3A%3Afuture%3A%3Apoll_fn%28move+%7Ccx%7C+iter.as_mut%28%29.poll_next%28cx%29%29%0A%7D%0A%0A%2F%2F+An+async+generator+function%21+As+of+December+2025%2C+this+syntax+is%0A%2F%2F+nightly-only.%0Aasync+gen+fn+double_each%28mut+channel%3A+UnboundedReceiver%3Ci32%3E%29+-%3E+i32+%7B%0A++++while+let+Some%28n%29+%3D+channel.recv%28%29.await+%7B%0A++++++++yield+2+*+n%3B%0A++++%7D%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++%2F%2F+Open+a+channel+and+spawn+a+background+task+that+sends+a+number+into%0A++++%2F%2F+it+every+second.%0A++++let+%28send%2C+recv%29+%3D+tokio%3A%3Async%3A%3Ampsc%3A%3Aunbounded_channel%28%29%3B%0A++++tokio%3A%3Aspawn%28async+move+%7B%0A++++++++for+i+in+1..%3D5+%7B%0A++++++++++++send.send%28i%29.unwrap%28%29%3B%0A++++++++++++sleep%28Duration%3A%3Afrom_secs%281%29%29.await%3B%0A++++++++%7D%0A++++%7D%29%3B%0A++++%2F%2F+Pass+the+receive+end+of+the+channel+to+an+%60async+gen%60+function+that%0A++++%2F%2F+doubles+each+element%2C+and+loop+over+the+results.%0A++++let+mut+stream+%3D+pin%21%28double_each%28recv%29%29%3B%0A++++while+let+Some%28n%29+%3D+next%28stream.as_mut%28%29%29.await+%7B%0A++++++++dbg%21%28n%29%3B%0A++++%7D%0A%7D

play.rust-lang.org

https://docs.rs/futures/latest/futures/stream/fn.iter.html

docs.rs

https://docs.rs/futures/latest/futures/stream/fn.once.html

docs.rs

https://play.rust-lang.org/?edition=2024&code=use+futures%3A%3AStreamExt%3B%0Ause+futures%3A%3Alock%3A%3AMutex%3B%0Ause+std%3A%3Async%3A%3ALazyLock%3B%0Ause+std%3A%3Atime%3A%3ADuration%3B%0A%0A%2F%2F+This+mutex+implementation+is+unfair%21+%28It+also+doesn%27t+have+a+const+new%0A%2F%2F+function%2C+so+we+need+a+%60LazyLock%60+to+initialize+it.%29%0Astatic+LOCK%3A+LazyLock%3CMutex%3C%28%29%3E%3E+%3D+LazyLock%3A%3Anew%28%7C%7C+Mutex%3A%3Anew%28%28%29%29%29%3B%0A%0Aasync+fn+foo%28%29+%7B%0A++++let+guard+%3D+LOCK.lock%28%29.await%3B%0A++++tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%2810%29%29.await%3B%0A++++drop%28guard%29%3B%0A++++%2F%2F+This+second+sleep+allows+the+second+%60foo%60+to+acquire+the+lock+before%0A++++%2F%2F+the+first+%60foo%60+finishes+below.+If+you+comment+it+out%2C+the+deadlock%0A++++%2F%2F+no+longer+appears.+%28The+original+version+of+this+example+using+a%0A++++%2F%2F+%60tokio%3A%3Async%3A%3AMutex%60+didn%27t+need+this%2C+because+that+mutex+is+fair.%29%0A++++tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%285%29%29.await%3B%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++futures%3A%3Astream%3A%3Aiter%28%5Bfoo%28%29%2C+foo%28%29%5D%29%0A++++++++.buffered%282%29%0A++++++++.for_each%28async+%7C_%7C+%7B%0A++++++++++++println%21%28%22We+make+it+here...%22%29%3B%0A++++++++++++foo%28%29.await%3B%0A++++++++++++println%21%28%22...but+not+here%21%22%29%3B%0A++++++++%7D%29%0A++++++++.await%3B%0A%7D

play.rust-lang.org

https://docs.rs/futures/latest/futures/stream/struct.FuturesOrdered.html

docs.rs

https://docs.rs/futures/latest/futures/stream/struct.FuturesUnordered.html

docs.rs

https://devblogs.microsoft.com/oldnewthing/20150814-00/?p=91811

devblogs.microsoft.com

https://users.rust-lang.org/t/pthread-cancel-undefined-behavior/38477/3

users.rust-lang.org

https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-terminatethread

learn.microsoft.com

https://play.rust-lang.org/?edition=2024&code=use+std%3A%3Aos%3A%3Aunix%3A%3Aprocess%3A%3ACommandExt%3B%0Ause+std%3A%3Athread%3B%0Ause+std%3A%3Atime%3A%3ADuration%3B%0A%0Astatic+LOCK%3A+std%3A%3Async%3A%3AMutex%3C%28%29%3E+%3D+std%3A%3Async%3A%3AMutex%3A%3Anew%28%28%29%29%3B%0A%0Afn+foo%28%29+%7B%0A++++let+_guard+%3D+LOCK.lock%28%29.unwrap%28%29%3B%0A++++%2F%2F+Use+a+longer+sleep+in+this+example%2C+to+account+for+child+process%0A++++%2F%2F+spawning+time.%0A++++thread%3A%3Asleep%28Duration%3A%3Afrom_millis%281000%29%29%3B%0A%7D%0A%0Afn+main%28%29+-%3E+std%3A%3Aio%3A%3AResult%3C%28%29%3E+%7B%0A++++%2F%2F+Spawn+a+background+thread+that+calls+foo%28%29.%0A++++thread%3A%3Aspawn%28foo%29%3B%0A++++%2F%2F+Sleep+to+give+the+background+thread+time+to+take+%60LOCK%60.%0A++++thread%3A%3Asleep%28Duration%3A%3Afrom_millis%28500%29%29%3B%0A++++%2F%2F+Fork+a+child+process+while+%60LOCK%60+is+held.%0A++++let+mut+command+%3D+std%3A%3Aprocess%3A%3ACommand%3A%3Anew%28%22echo%22%29%3B%0A++++unsafe+%7B%0A++++++++command.pre_exec%28%7C%7C+%7B%0A++++++++++++%2F%2F+This+closure+runs+post-fork-pre-exec+in+the+child.%0A++++++++++++println%21%28%22We+make+it+here...%22%29%3B%0A++++++++++++foo%28%29%3B%0A++++++++++++println%21%28%22...but+not+here%21%22%29%3B%0A++++++++++++Ok%28%28%29%29%0A++++++++%7D%29%3B%0A++++%7D%3B%0A++++command.status%28%29%3F%3B%0A++++Ok%28%28%29%29%0A%7D

play.rust-lang.org

https://www.microsoft.com/en-us/research/wp-content/uploads/2019/04/fork-hotos19.pdf

microsoft.com

https://man7.org/linux/man-pages/man3/pthread_atfork.3.html

man7.org

https://man7.org/linux/man-pages/man3/pthread_cleanup_push.3.html

man7.org

https://man7.org/linux/man-pages/man3/pthread_setcancelstate.3.html

man7.org

https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-suspendthread

learn.microsoft.com

https://play.rust-lang.org/?edition=2024&code=use+std%3A%3Athread%3B%0Ause+std%3A%3Atime%3A%3ADuration%3B%0A%0Astatic+LOCK%3A+std%3A%3Async%3A%3AMutex%3C%28%29%3E+%3D+std%3A%3Async%3A%3AMutex%3A%3Anew%28%28%29%29%3B%0A%0Afn+foo%28%29+%7B%0A++++let+_guard+%3D+LOCK.lock%28%29.unwrap%28%29%3B%0A++++%2F%2F+Use+a+longer+sleep+in+this+example%2C+to+account+for+child+process%0A++++%2F%2F+spawning+time.%0A++++thread%3A%3Asleep%28Duration%3A%3Afrom_millis%281000%29%29%3B%0A%7D%0A%0Aextern+%22C%22+fn+foo_signal_handler%28_signum%3A+libc%3A%3Ac_int%29+%7B%0A++++%2F%2F+Printing+in+signal+handlers+isn%27t+really+allowed%2C+but+neither+is%0A++++%2F%2F+taking+locks%2C+in+part+because+of+exactly+the+sort+of+deadlocks+we%27re%0A++++%2F%2F+demonstrating+here.+It+works+in+this+case.%0A++++println%21%28%22We+make+it+here...%22%29%3B%0A++++foo%28%29%3B%0A++++println%21%28%22...but+not+here%21%22%29%3B%0A%7D%0A%0Afn+main%28%29+-%3E+std%3A%3Aio%3A%3AResult%3C%28%29%3E+%7B%0A++++%2F%2F+Set+a+signal+handler+for+SIGUSR1+that+calls+foo%28%29.%0A++++unsafe+%7B%0A++++++++libc%3A%3Asignal%28libc%3A%3ASIGUSR1%2C+foo_signal_handler+as+*const+%28%29+as+_%29%3B%0A++++%7D%0A++++%2F%2F+Spawn+a+child+process+that+sends+us+SIGUSR1+after+500+ms.%0A++++std%3A%3Aprocess%3A%3ACommand%3A%3Anew%28%22bash%22%29%0A++++++++.arg%28%22-c%22%29%0A++++++++.arg%28format%21%28%22sleep+0.5+%26%26+kill+-USR1+%7B%7D%22%2C+std%3A%3Aprocess%3A%3Aid%28%29%29%29%0A++++++++.spawn%28%29%3F%3B%0A++++%2F%2F+Call+%60foo%60+ourselves.+We%27ll+be+in+this+call+and+holding+%60LOCK%60+in%0A++++%2F%2F+%7E500+ms+when+SIGUSR1+arrives+and+the+signal+handler+fires.+It%27ll%0A++++%2F%2F+hijack+this+thread%2C+try+to+take+%60LOCK%60+again%2C+and+deadlock.%0A++++foo%28%29%3B%0A++++Ok%28%28%29%29%0A%7D

play.rust-lang.org

signalfd is useless Read at the source ↗

ldpreload.com

https://oxide-and-friends.transistor.fm/episodes/futurelock/transcript

oxide-and-friends.transistor.fm

https://devblogs.microsoft.com/oldnewthing/20031209-00/?p=41573

devblogs.microsoft.com

Async cancellation: a case study of pub-sub in mini-redis Read at the source ↗

smallcultfollowing.com

https://play.rust-lang.org/?edition=2024&code=use+futures%3A%3A%7BStreamExt%2C+stream%7D%3B%0Ause+std%3A%3Apin%3A%3Apin%3B%0Ause+std%3A%3Atime%3A%3ADuration%3B%0Ause+tokio%3A%3Atime%3A%3Atimeout%3B%0A%0Astatic+LOCK%3A+tokio%3A%3Async%3A%3AMutex%3C%28%29%3E+%3D+tokio%3A%3Async%3A%3AMutex%3A%3Aconst_new%28%28%29%29%3B%0A%0Aasync+fn+foo%28%29+%7B%0A++++let+_guard+%3D+LOCK.lock%28%29.await%3B%0A++++tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%2810%29%29.await%3B%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++let+mut+stream+%3D+pin%21%28stream%3A%3Aonce%28foo%28%29%29%29%3B%0A++++_+%3D+timeout%28Duration%3A%3Afrom_millis%285%29%2C+stream.next%28%29%29.await%3B%0A++++println%21%28%22We+make+it+here...%22%29%3B%0A++++foo%28%29.await%3B%0A++++println%21%28%22...but+not+here%21%22%29%3B%0A%7D

play.rust-lang.org

https://docs.rs/tokio/latest/tokio/task/fn.spawn.html

docs.rs

https://github.com/nikomatsakis/moro

github.com

https://doc.rust-lang.org/std/thread/fn.scope.html

doc.rust-lang.org

The Scoped Task trilemma Read at the source ↗

without.boats

https://github.com/tokio-rs/mini-redis/blob/e186482ca00f8d884ddcbe20417f3654d03315a4/src/cmd/subscribe.rs

github.com

https://github.com/oconnor663/join_me_maybe

github.com

https://github.com/oconnor663/join_me_maybe/

github.com

https://github.com/oconnor663/omicron/pull/1

github.com

https://github.com/oconnor663/mini-redis/pull/1

github.com

https://docs.rs/tokio-stream/latest/tokio_stream/trait.StreamExt.html

docs.rs

Asynchronous clean-up Read at the source ↗

without.boats

https://github.com/rust-lang/rust/issues/118898

github.com

Three problems of pinning Read at the source ↗

without.boats

https://old.reddit.com/r/rust/comments/1risdcd/never_snooze_a_future/o88d0ft/

old.reddit.com

https://docs.rs/futures/latest/futures/future/fn.select.html

docs.rs

https://play.rust-lang.org/?edition=2024&code=use+std%3A%3Atime%3A%3ADuration%3B%0A%0Astatic+LOCK%3A+tokio%3A%3Async%3A%3AMutex%3C%28%29%3E+%3D+tokio%3A%3Async%3A%3AMutex%3A%3Aconst_new%28%28%29%29%3B%0A%0Aasync+fn+foo%28%29+%7B%0A++++let+_guard+%3D+LOCK.lock%28%29.await%3B%0A++++tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%2810%29%29.await%3B%0A%7D%0A%0A%23%5Btokio%3A%3Amain%5D%0Aasync+fn+main%28%29+%7B%0A++++%2F%2F+If+we+didn%27t+capture+%60_output%60+here%2C+this+example+wouldn%27t+deadlock.%0A++++%2F%2F+But+this+%60select%60+function+%28not+the+%60select%21%60+macro%29+returns+a+tuple%0A++++%2F%2F+of+one+output+and+one+future+%28the+%22loser%22%29.+If+we+don%27t+either+let%0A++++%2F%2F+that+future+drop+or+keep+polling+it%2C+then+we%27re+snoozing+it.%0A++++let+_output+%3D+futures%3A%3Afuture%3A%3Aselect%28%0A++++++++Box%3A%3Apin%28foo%28%29%29%2C%0A++++++++Box%3A%3Apin%28tokio%3A%3Atime%3A%3Asleep%28Duration%3A%3Afrom_millis%285%29%29%29%2C%0A++++%29%0A++++.await%3B%0A++++println%21%28%22We+make+it+here...%22%29%3B%0A++++foo%28%29.await%3B%0A++++println%21%28%22...but+not+here%21%22%29%3B%0A%7D

play.rust-lang.org

https://doc.rust-lang.org/std/marker/trait.Unpin.html

doc.rust-lang.org

https://old.reddit.com/r/rust/comments/1risdcd/never_snooze_a_future/

old.reddit.com

https://lobste.rs/s/isuqoa/never_snooze_future

lobste.rs

https://news.ycombinator.com/item?id=47296426

news.ycombinator.com

Elsewhere on jacko.io (1)

https://jacko.io//async_intro.html

jacko.io