Add `ParallelGuard` type to handle unwinding in parallel sections #115144

Zoxc · 2023-08-23T18:53:52Z

This adds a ParallelGuard type to handle unwinding in parallel sections instead of manually dealing with panics in each parallel operation. This also adds proper panic handling to the join operation.

cc @SparrowLii

rustbot · 2023-08-23T18:53:57Z

r? @compiler-errors

(rustbot has picked a reviewer for you, use r? to override)

tests/ui/const-generics/late-bound-vars/in_closure.rs

compiler-errors

r=me with or without

compiler-errors · 2023-08-23T20:58:02Z

compiler/rustc_data_structures/src/sync.rs

+/// continuing with unwinding. It's also used for the non-parallel code to ensure error message
+/// output match the parallel compiler for testing purposes.
+pub struct ParallelGuard {
+    panic: Lock<Option<Box<dyn Any + std::marker::Send + 'static>>>,


Should we implement Drop for ParallelGuard to make sure we never drop a panic on the floor without handling it? unwind will need to get reworked below if so.

I initially went for Drop, but I ended up preferring the explicit unwinding of the unwind calls.

I think having the explicit unwind calls is better. I just wonder if we should protect against missing unwind calls somehow... anyways, I don't feel particularly strongly about it.

compiler-errors · 2023-08-23T20:58:13Z

@bors delegate+

bors · 2023-08-23T20:58:15Z

✌️ @Zoxc, you can now approve this pull request!

If @compiler-errors told you to "r=me" after making some further change, please make that change, then do @bors r=@compiler-errors

Zoxc · 2023-08-23T23:08:55Z

@bors r=@compiler-errors

bors · 2023-08-23T23:08:57Z

📌 Commit d0a3e77e7b4c4c787451780e8abeb3eab4ec4353 has been approved by compiler-errors

It is now in the queue for this repository.

Zoxc · 2023-08-24T00:57:27Z

I've changed to the Lock to Mutex for compatibility with #111713, since Lock no longer use Sync / Send traits and can't be used with Rayon.

SparrowLii · 2023-08-24T01:02:24Z

Thanks!

bjorn3 · 2023-08-24T09:15:07Z

compiler/rustc_data_structures/src/sync.rs

-                    resume_unwind(panic);
-                }
+                let guard = ParallelGuard::new();
+                let r = t.into_iter().filter_map(|i| guard.run(|| map(i))).collect();


Wouldn't this non-deterministically pick one of the panics if multiple happen? For FatalErrorMarker that is fine as it is a ZST, but for other panics it may not be.

I don't see why that would be problematic. No panic would be guaranteed to "win" in a concurrent setting. FatalErrorMarker is the only exception (not technically a panic) that we need to handle.

Zoxc · 2023-08-26T14:44:14Z

I've changed this to use a function taking a closure, that way unwinding is guaranteed to be done if needed.

SparrowLii · 2023-08-29T12:09:00Z

@Zoxc I think you have to r=reviewer again

Zoxc · 2023-08-29T18:46:52Z

I think the changes is significant enough to warrant a re-review.

@rustbot ready

compiler-errors · 2023-08-30T01:55:12Z

@bors r+

bors · 2023-08-30T01:55:14Z

📌 Commit 9074443d3f84d7f7ae5e110f6f92100ddf8c344f has been approved by compiler-errors

It is now in the queue for this repository.

bors · 2023-08-30T10:44:48Z

☔ The latest upstream changes (presumably #111713) made this pull request unmergeable. Please resolve the merge conflicts.

Zoxc · 2023-08-30T17:07:43Z

@bors r=@compiler-errors

bors · 2023-08-30T17:18:29Z

📌 Commit c303c8a has been approved by compiler-errors

It is now in the queue for this repository.

bors · 2023-08-30T19:33:16Z

⌛ Testing commit c303c8a with merge 59a8294...

bors · 2023-08-30T21:21:20Z

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing 59a8294 to master...

rust-timer · 2023-08-31T10:22:32Z

Finished benchmarking commit (59a8294): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.4%, -0.4%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.9%	[0.5%, 1.3%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.6%	[-2.0%, -1.2%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-2.0%, 1.3%]	4

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.5%]	1
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 630.996s -> 633.863s (0.45%)
Artifact size: 316.52 MiB -> 316.71 MiB (0.06%)

rustbot assigned compiler-errors Aug 23, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 23, 2023

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bjorn3 reviewed Aug 24, 2023

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SparrowLii mentioned this pull request Aug 26, 2023

Tracking Issue for Parallel Rustc Front-end #113349

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rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 29, 2023

compiler-errors approved these changes Aug 30, 2023

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bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Aug 30, 2023

Zoxc added 2 commits August 30, 2023 18:12

Make parallel! an expression

51eb842

Add ParallelGuard type to handle unwinding in parallel sections

b56acac

Zoxc added 3 commits August 30, 2023 18:13

Update failure status

2428054

Use Mutex to avoid issue with conditional locks

d36393b

Use a parallel_guard function to handle the parallel guard

c303c8a

Zoxc force-pushed the parallel-guard branch from 9074443 to c303c8a Compare August 30, 2023 16:18

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 30, 2023

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 30, 2023

bors merged commit 59a8294 into rust-lang:master Aug 30, 2023
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rustbot added this to the 1.74.0 milestone Aug 30, 2023

Zoxc deleted the parallel-guard branch August 30, 2023 21:49

bors mentioned this pull request Aug 30, 2023

Increase parallelism in various locations #115003

Open

matthiaskrgr mentioned this pull request Nov 1, 2023

wrong exit code after ICE #116659

Closed

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Add `ParallelGuard` type to handle unwinding in parallel sections #115144

Add `ParallelGuard` type to handle unwinding in parallel sections #115144

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Add ParallelGuard type to handle unwinding in parallel sections #115144

Add ParallelGuard type to handle unwinding in parallel sections #115144

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Overall result: ✅ improvements - no action needed

Add `ParallelGuard` type to handle unwinding in parallel sections #115144

Add `ParallelGuard` type to handle unwinding in parallel sections #115144

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