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Remove synchronization from Windows hashmap_random_keys #99371

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merged 1 commit into from
Aug 3, 2022
Merged

Remove synchronization from Windows hashmap_random_keys #99371

merged 1 commit into from
Aug 3, 2022

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ChrisDenton
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@ChrisDenton ChrisDenton commented Jul 17, 2022 •
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Unfortunately using synchronization when generating hashmap keys can prevent it being used in DllMain.

Fixes #99341

@rustbot rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Jul 17, 2022
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rustbot commented Jul 17, 2022

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

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@ChrisDenton: no appropriate reviewer found, use r? to override

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 17, 2022
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ChrisDenton commented Jul 17, 2022 •
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r? rust-lang/libs

@ChrisDenton ChrisDenton added the O-windows Operating system: Windows label Jul 17, 2022
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r? libs

@rust-highfive rust-highfive assigned thomcc and unassigned kennytm Aug 2, 2022
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thomcc approved these changes Aug 2, 2022
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I don't think it's that unfortunate. This is a lot cleaner anyway, and should be more efficient for cases that don't need the fallback.

In the future if we care about the cost of the extra syscall when BCryptGenRandom isn't supported, we could use an AtomicPtr to recover that1

That said, thiis seems more robust than that would be, and I suspect optimizing for the "no BCryptGenRandom" case doesn't matter.

Footnotes

  1. It would start out as preferred_rng, and get assigned to fallback_rng on error. This is similar to how we handle the flags we use for getrandom on linux. ↩

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thomcc commented Aug 2, 2022

@bors r+

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bors commented Aug 2, 2022

📌 Commit 46673bb has been approved by thomcc

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 2, 2022
@thomcc thomcc mentioned this pull request Aug 2, 2022
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@Dylan-DPC Dylan-DPC mentioned this pull request Aug 3, 2022
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bors added a commit to rust-lang-ci/rust that referenced this pull request Aug 3, 2022
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Auto merge of rust-lang#100100 - Dylan-DPC:rollup-llcaaq8, r=Dylan-DPC
7308c22 
Rollup of 5 pull requests

Successful merges:

 - rust-lang#99371 (Remove synchronization from Windows `hashmap_random_keys`)
 - rust-lang#99614 (do not claim that transmute is like memcpy)
 - rust-lang#99738 (rustdoc: avoid inlining modules with duplicate names)
 - rust-lang#99800 (Fix futex module imports on wasm+atomics)
 - rust-lang#100079 (Replace `* -> vec` with `-> vec` in docs)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 5730f12 into rust-lang:master Aug 3, 2022
@rustbot rustbot added this to the 1.64.0 milestone Aug 3, 2022
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@thomcc thomcc thomcc approved these changes

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O-windows Operating system: Windows S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-libs Relevant to the library team, which will review and decide on the PR/issue.
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Successfully merging this pull request may close these issues.

std::collections::hash::map::new stuck on Windows 7
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