task: Drop the join waker of a task eagerly when the JoinHandle gets dropped or the task completes #6986
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dropped or the task completes Currently, the waker registered with a JoinHandle is not dropped until the task allocation is dropped. This behaviour may cause the memory allocated by a task to not be freed when in the case of two tasks awaiting each others JoinHandle. This commit changes the behaviour by actively dropping the waker when the JoinHandle gets dropped (or the task completes in some cases).
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Darksonn
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Nov 25, 2024
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Darksonn
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Dec 4, 2024
* `State::transition_do_join_handle_drop` now returns a struct with to booleans to indicate what the JoinHandle should drop * Use `fetch_and` when unsetting JOIN_WAKER after COMPLETE
Darksonn
reviewed
Dec 5, 2024
* Added missing ';' after unsafe blocks * Improved documentation in `State::transition_to_join_handle_dropped` on the scenarios in which `JOIN_WAKER` gets unset
Darksonn
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Dec 9, 2024
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ref cycle test into a non-loom test (leaks will be detected by miri)
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Darksonn
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Dec 29, 2024
tokio/src/runtime/tests/task.rs
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| #[test] | ||
| fn drop_tasks_with_reference_cycle() { |
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This does not use any Tokio internals, so it does not need to be inside src/. It should be in tokio/tests/ instead.
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Oh thanks I wasnt aware of this but will keep it in mind for the future.
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No worries. Thanks a lot for the PR!
This was referenced Jan 6, 2025
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⚠️ Dependabot is rebasing this PR⚠️ Rebasing might not happen immediately, so don't worry if this takes some time. Note: if you make any changes to this PR yourself, they will take precedence over the rebase. Bumps tokio from 1.42.0 to 1.43.0. Release notes Sourced from tokio's releases. Tokio v1.43.0 1.43.0 (Jan 8th, 2025) Added net: add UdpSocket::peek methods (#7068) net: add support for Haiku OS (#7042) process: add Command::into_std() (#7014) signal: add SignalKind::info on illumos (#6995) signal: add support for realtime signals on illumos (#7029) Fixed io: don't call set_len before initializing vector in Blocking (#7054) macros: suppress clippy::needless_return in #[tokio::main] (#6874) runtime: fix thread parking on WebAssembly (#7041) Changes chore: use unsync loads for unsync_load (#7073) io: use Buf::put_bytes in Repeat read impl (#7055) task: drop the join waker of a task eagerly (#6986) Changes to unstable APIs metrics: improve flexibility of H2Histogram Configuration (#6963) taskdump: add accessor methods for backtrace (#6975) Documented io: clarify ReadBuf::uninit allows initialized buffers as well (#7053) net: fix ambiguity in TcpStream::try_write_vectored docs (#7067) runtime: fix LocalRuntime doc links (#7074) sync: extend documentation for watch::Receiver::wait_for (#7038) sync: fix typos in OnceCell docs (#7047) #6874: tokio-rs/tokio#6874 #6963: tokio-rs/tokio#6963 #6975: tokio-rs/tokio#6975 #6986: tokio-rs/tokio#6986 #6995: tokio-rs/tokio#6995 #7014: tokio-rs/tokio#7014 #7029: tokio-rs/tokio#7029 #7038: tokio-rs/tokio#7038 #7041: tokio-rs/tokio#7041 #7042: tokio-rs/tokio#7042 #7047: tokio-rs/tokio#7047 #7053: tokio-rs/tokio#7053 #7054: tokio-rs/tokio#7054 #7055: tokio-rs/tokio#7055 ... (truncated) Commits 5f3296d chore: prepare Tokio v1.43.0 (#7079) cc974a6 chore: prepare tokio-macros v2.5.0 (#7078) 15495fd metrics: improve flexibility of H2Histogram Configuration (#6963) ad41834 io: don't call set_len before initializing vector in Blocking (#7054) bd3e857 runtime: move is_join_waker_set assertion in unset_waker (#7072) 15f7366 runtime: fix LocalRuntime doc links (#7074) fd2048d ci: split miri jobs into unit and integration tests (#7071) e8f3915 chore: use unsync loads for unsync_load (#7073) 67f1277 net: fix ambiguity in TcpStream::try_write_vectored docs (#7067) 463502c io: clarify ReadBuf::uninit allows initialized buffers as well (#7053) Additional commits viewable in compare view Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase. Dependabot commands and options You can trigger Dependabot actions by commenting on this PR: @dependabot rebase will rebase this PR @dependabot recreate will recreate this PR, overwriting any edits that have been made to it @dependabot merge will merge this PR after your CI passes on it @dependabot squash and merge will squash and merge this PR after your CI passes on it @dependabot cancel merge will cancel a previously requested merge and block automerging @dependabot reopen will reopen this PR if it is closed @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually @dependabot show <dependency name> ignore conditions will show all of the ignore conditions of the specified dependency @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
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Motivation
Currently, the waker registered with a JoinHandle is not dropped until the task allocation is dropped. This behaviour may cause the memory allocated by a task to not be freed when in the case of two tasks awaiting each others JoinHandle.
See #6505 for more details.
Solution
To prevent this we need to actively drop the waker when the
JoinHandlegets dropped (or the task completes in some cases).Closes #6505.