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time: Do not overflow to signal value #5710

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Erk-
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@Erk- Erk- commented May 23, 2023

Motivation

As described in #5183, Tokio will panic if you sleep far, but not too far into the future.
This can cause issues and crashes in some cases where you don't expect it which is the main motivation for solving it.

Solution

The issue is that the time value will overflow and then get set to u64::MAX, u64::MAX is also used as the signal value for the state STATE_DEREGISTERED which will cause the when function to think that the time already have fired and thus been deregistered.

If the program is run in debug mode it will fail a bit earlier because of a debug_assert

Issue with this PR

This PR will currently never complete CI since the test I have added fails to ever complete. I am not sure how that should be resolved so I have opened this PR to discuss it as well. Should it be commented out or can it be made to work instead.

@github-actions github-actions bot added the R-loom Run loom tests on this PR label May 23, 2023
@Darksonn Darksonn added A-tokio Area: The main tokio crate M-time Module: tokio/time labels May 23, 2023
tokio/tests/time_sleep.rs Outdated Show resolved Hide resolved
Hocuri added a commit to deltachat/deltachat-core-rust that referenced this pull request May 23, 2023
This might not be needed after all because of
tokio-rs/tokio#5710, but since I already wrote
the code, I created a PR anyway.
@Erk- Erk- force-pushed the fix/far-out-in-the-future-but-not-too-far branch from de05c50 to 009614c Compare May 23, 2023 08:59
Durations far into the future would cause the conversion of millis
from u128 to u64 to fail and set the value to u64::MAX. This in turn
causes issues since u64::MAX is used as a signal value.

This patch adds a new constant that is the largest non-signal value
that can be used for ticks. And uses that in the location it causes
issues.
@Erk- Erk- force-pushed the fix/far-out-in-the-future-but-not-too-far branch from 009614c to 48cdd43 Compare May 23, 2023 09:03
tokio/tests/time_sleep.rs Outdated Show resolved Hide resolved
@Erk- Erk- requested a review from Darksonn June 10, 2023 11:05
@Erk- Erk- force-pushed the fix/far-out-in-the-future-but-not-too-far branch from bb0e8ed to 0015c26 Compare June 10, 2023 11:20
let big = std::time::Duration::from_secs(u64::MAX / 10);
// This is a workaround since awaiting sleep(big) will never finish.
tokio::select! {
biased;
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Suggested change
biased;
biased;

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I had it like that at first, but rustfmt disagree with it, so I have skipped the expression now.

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Huh? Rustfmt usually does not format macros. Can you try and remove the skip annotation to see if our CI fails it?

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@Erk- Erk- Jun 10, 2023

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It did hence the force push above, here is the specific run of the CI
https://github.com/tokio-rs/tokio/actions/runs/5229606790/jobs/9442690852

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Weird. Oh well.

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Thanks.

@Darksonn Darksonn merged commit 2a54ad0 into tokio-rs:master Jun 10, 2023
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Hocuri commented Jun 11, 2023

Great, thanks a huge lot @Erk-, and @Darksonn for reviewing !

crapStone pushed a commit to Calciumdibromid/CaBr2 that referenced this pull request Jul 6, 2023
This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dependencies | minor | `1.28.2` -> `1.29.1` |
| [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dev-dependencies | minor | `1.28.2` -> `1.29.1` |

---

### Release Notes

<details>
<summary>tokio-rs/tokio (tokio)</summary>

### [`v1.29.1`](https://github.com/tokio-rs/tokio/releases/tag/tokio-1.29.1): Tokio v1.29.1

[Compare Source](tokio-rs/tokio@tokio-1.29.0...tokio-1.29.1)

##### Fixed

-   rt: fix nesting two `block_in_place` with a `block_on` between (#&#8203;5837])

#&#8203;5837]: tokio-rs/tokio#5837

### [`v1.29.0`](https://github.com/tokio-rs/tokio/releases/tag/tokio-1.29.0): Tokio v1.29.0

[Compare Source](tokio-rs/tokio@tokio-1.28.2...tokio-1.29.0)

Technically a breaking change, the `Send` implementation is removed from
`runtime::EnterGuard`. This change fixes a bug and should not impact most users.

##### Breaking

-   rt: `EnterGuard` should not be `Send` (#&#8203;5766])

##### Fixed

-   fs: reduce blocking ops in `fs::read_dir` (#&#8203;5653])
-   rt: fix possible starvation (#&#8203;5686], #&#8203;5712])
-   rt: fix stacked borrows issue in `JoinSet` (#&#8203;5693])
-   rt: panic if `EnterGuard` dropped incorrect order (#&#8203;5772])
-   time: do not overflow to signal value (#&#8203;5710])
-   fs: wait for in-flight ops before cloning `File` (#&#8203;5803])

##### Changed

-   rt: reduce time to poll tasks scheduled from outside the runtime (#&#8203;5705], #&#8203;5720])

##### Added

-   net: add uds doc alias for unix sockets (#&#8203;5659])
-   rt: add metric for number of tasks (#&#8203;5628])
-   sync: implement more traits for channel errors (#&#8203;5666])
-   net: add nodelay methods on TcpSocket (#&#8203;5672])
-   sync: add `broadcast::Receiver::blocking_recv` (#&#8203;5690])
-   process: add `raw_arg` method to `Command` (#&#8203;5704])
-   io: support PRIORITY epoll events (#&#8203;5566])
-   task: add `JoinSet::poll_join_next` (#&#8203;5721])
-   net: add support for Redox OS (#&#8203;5790])

##### Unstable

-   rt: add the ability to dump task backtraces (#&#8203;5608], #&#8203;5676], #&#8203;5708], #&#8203;5717])
-   rt: instrument task poll times with a histogram (#&#8203;5685])

#&#8203;5766]: tokio-rs/tokio#5766

#&#8203;5653]: tokio-rs/tokio#5653

#&#8203;5686]: tokio-rs/tokio#5686

#&#8203;5712]: tokio-rs/tokio#5712

#&#8203;5693]: tokio-rs/tokio#5693

#&#8203;5772]: tokio-rs/tokio#5772

#&#8203;5710]: tokio-rs/tokio#5710

#&#8203;5803]: tokio-rs/tokio#5803

#&#8203;5705]: tokio-rs/tokio#5705

#&#8203;5720]: tokio-rs/tokio#5720

#&#8203;5659]: tokio-rs/tokio#5659

#&#8203;5628]: tokio-rs/tokio#5628

#&#8203;5666]: tokio-rs/tokio#5666

#&#8203;5672]: tokio-rs/tokio#5672

#&#8203;5690]: tokio-rs/tokio#5690

#&#8203;5704]: tokio-rs/tokio#5704

#&#8203;5566]: tokio-rs/tokio#5566

#&#8203;5721]: tokio-rs/tokio#5721

#&#8203;5790]: tokio-rs/tokio#5790

#&#8203;5608]: tokio-rs/tokio#5608

#&#8203;5676]: tokio-rs/tokio#5676

#&#8203;5708]: tokio-rs/tokio#5708

#&#8203;5717]: tokio-rs/tokio#5717

#&#8203;5685]: tokio-rs/tokio#5685

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about these updates again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNi4wLjAiLCJ1cGRhdGVkSW5WZXIiOiIzNi4wLjAiLCJ0YXJnZXRCcmFuY2giOiJkZXZlbG9wIn0=-->

Co-authored-by: cabr2-bot <cabr2.help@gmail.com>
Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1958
Reviewed-by: crapStone <crapstone01@gmail.com>
Co-authored-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
Co-committed-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
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4 participants