compiler_fence documentation: emphasize synchronization, not reordering #129856
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
rustbot
added
S-waiting-on-review
RalfJung
force-pushed
the
compiler_fence
branch
from
7408a3f to
32a30dd
Compare
|
Ideally, I'd remove all of the mentions of reordering from the docs. Otherwise, looks to be correct. |
Yeah... I didn't dare suggest that as it is such a common thing to talk about in weak memory models. So I opted for just emphasizing them less. |
thomcc
approved these changes
Sep 2, 2024
| /// | ||
| /// The re-ordering prevented by the different ordering semantics are: | ||
| /// See [`fence`] for how a fence can be used to achieve synchronization. Note that just like | ||
| /// [`fence`], synchronization still requires atomic operations to be used in both threads -- it is |
There was a problem hiding this comment.
TIL, I thought they could be volatile too.
There was a problem hiding this comment.
Yeah would be nice to use this for volatile ordering, but that's not per-spec... and IMO the fix for that is to make volatile operations also be atomic, but that project has stalled it seems.
|
@bors r+ rollup |
bors
added
S-waiting-on-bors
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Sep 2, 2024
…iaskrgr Rollup of 12 pull requests Successful merges: - rust-lang#129748 (Box validity: update for new zero-sized rules) - rust-lang#129829 (Make decoding non-optional `LazyArray` panic if not set) - rust-lang#129856 (compiler_fence documentation: emphasize synchronization, not reordering) - rust-lang#129868 (Remove kobzol vacation status) - rust-lang#129875 (chore: Fix typos in 'compiler' (batch 1)) - rust-lang#129877 (chore: Fix typos in 'compiler' (batch 2)) - rust-lang#129878 (chore: Fix typos in 'compiler' (batch 3)) - rust-lang#129890 (Remove stray word in a comment) - rust-lang#129892 (Clarify language around ptrs in slice::raw) - rust-lang#129905 (mailmap: add new email for davidtwco) - rust-lang#129906 (mailmapper?) - rust-lang#129907 (Fix compile error in solid's remove_dir_all) r? `@ghost` `@rustbot` modify labels: rollup
rust-timer
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Sep 3, 2024
Rollup merge of rust-lang#129856 - RalfJung:compiler_fence, r=thomcc compiler_fence documentation: emphasize synchronization, not reordering Our `fence` docs have at some point been update to explain that they are about synchronization, not about "preventing reordering". This updates the `compiler_fence` docs n the same vein, mostly by referring to the `fence` docs. The old docs make it sound like I can put a compiler_fence in the middle of a bunch of non-atomic operations and that would achieve any kind of guarantee. It does not, atomic operations are still required to do synchronization. I also slightly tweaked the `fence` docs, to put the synchronization first and the "prevent reordering" second. Cc `@rust-lang/opsem` `@chorman0773` `@m-ou-se` Fixes rust-lang#129189 Fixes rust-lang#54962
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Our
fencedocs have at some point been update to explain that they are about synchronization, not about "preventing reordering". This updates thecompiler_fencedocs n the same vein, mostly by referring to thefencedocs.The old docs make it sound like I can put a compiler_fence in the middle of a bunch of non-atomic operations and that would achieve any kind of guarantee. It does not, atomic operations are still required to do synchronization.
I also slightly tweaked the
fencedocs, to put the synchronization first and the "prevent reordering" second.Cc @rust-lang/opsem @chorman0773 @m-ou-se
Fixes #129189
Fixes #54962