[randomPoison]

#158782 introduced compile-time checks to verify that targets using the no-thread implementation of sync primitives are actually marked single-threaded. This broke the Trusty targets, which were not marked single-threaded. Trusty userspace doesn't have threads, so this PR updates the target definitions to properly mark them single-threaded.

@ahomescu please look this over and double check that this target change is correct.

Fixes #165596

LLM Usage Disclosure

I used an LLM in order to prepare this PR:

• An LLM found the target configuration option for marking a target single-threaded.
• An LLM found the PR that introduced the breakage so I could confirm what the fix should be.

[rustbot]

These commits modify compiler targets.
(See the Target Tier Policy.)

[rustbot]

r? @oli-obk

rustbot has assigned @oli-obk.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: compiler
• compiler expanded to 79 candidates
• Random selection from 20 candidates

[workingjubilee]

I checked the platform support page and it suggests these targets support threads: https://github.com/rust-lang/rust/blob/main/src/doc/rustc/src/platform-support/trusty.md

Can the platform document be updated to reflect the reality here? "It supports threads" when the support is fake is misleading.

[randomPoison]

Ah yeah you're right, that document is wrong :/ We should get that updated as well.

Also from some discussion with @ahomescu I'm not sure this is the right fix, we may need Trusty to have atomics support for the purpose of shared memory IPC. The better fix might be to implement the sync primitives via pthreads, which have a stubbed implementation on Trusty. I'm going to close this PR, but we can re-open it if it turns out that marking the targets single-threaded is the right solution.

[randomPoison]

@workingjubilee Oh, I think we both misread the target docs, it says "has limited support that excludes things like filesystem access, network I/O, and spawning processes/threads."

[workingjubilee]

...oops! Sorry about that, lol.