kmc-solid: Fix memory ordering in thread operations

[kawadakk]

Fixes two memory ordering issues in the thread state machine (ThreadInner::lifecycle) of the *-kmc-solid_* Tier 3 targets.

1. When detaching a thread that is still running (i.e., the owner updates lifecycle first, and the child updates it next), the first update did not synchronize-with the second update, resulting in a data race between the first update and the deallocation of ThreadInner by the child thread.
2. When joining on a thread, the joiner has to pass its own task ID to the joinee in order to be woken up later, but in doing so, it did not synchronize-with the read operation, creating possible sequences of execution where the joinee wakes up an incorrect or non-existent task.

Both issue are theoretical and most likely have never manifested in practice because of the stronger guarantees provided by the Arm memory model (particularly due to its barrier-based definition). Compiler optimizations could have subverted this, but the inspection of compiled code did not reveal such optimizations taking place.

[rustbot]

r? @m-ou-se

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

[rustbot]

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.

Examples of T-libs-api changes:

• Stabilizing library features
• Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

[rust-log-analyzer]

The job x86_64-gnu-tools failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

  IMAGE: x86_64-gnu-tools
##[endgroup]
From https://github.com/rust-lang/rust
 * branch              master     -> FETCH_HEAD
Searching for toolstate changes between b397bc0727ad27340466166455c6edd327a589c4 and 87252755c485a5004ebfa0f03b90897ec78e2dff
Tool subtrees were updated
##[group]Run src/ci/scripts/verify-channel.sh
src/ci/scripts/verify-channel.sh
shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}
env:
---
.......... (90/92)
..         (92/92)


/checkout/src/test/rustdoc-gui/basic-code.goml basic-code... FAILED
[ERROR] (line 3) Error: Execution context was destroyed, most likely because of a navigation.: for command `assert-count: (".src-line-numbers", 1)`
Build completed unsuccessfully in 0:02:21

[m-ou-se]

@bors r+

[bors]

📌 Commit 6fbef06 has been approved by m-ou-se

It is now in the queue for this repository.

[bors]

⌛ Testing commit 6fbef06 with merge 6ad8383...

[bors]

☀️ Test successful - checks-actions
Approved by: m-ou-se
Pushing 6ad8383 to master...

[rust-timer]

Finished benchmarking commit (6ad8383): 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)	-3.9%	[-3.9%, -3.9%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

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