Restrict aarch64 outline atomics to glibc for now. #90044

hkratz · 2021-10-19T08:14:55Z

The introduced dependency on getauxval causes linking problems with musl, making compiling any binaries for aarch64-unknown-linux-musl impossible without workarounds such as using lld or adding liblibc.rlib again to the linker invocation, see #89626.

This is a workaround until libc>0.2.108 is merged.

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rust-highfive · 2021-10-19T08:14:58Z

r? @oli-obk

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oli-obk · 2021-10-19T08:24:50Z

r? @workingjubilee

jbg · 2021-10-19T09:43:24Z

I may not understand how the features argument is interpreted, but shouldn't this be before the -C target-feature processing on line 417? It should be defaulting outline-atomics to on, but right now it seems to be forcing it to on, so -C target-feature=-outline-atomics doesn't do anything.

For example, right now you can't get a successful build on aarch64-unknown-linux-musl by setting RUSTFLAGS="-C target-feature=-outline-atomics". Presumably even after this patch, a glibc user can't disable the outline-atomics target feature if they want to.

hkratz · 2021-10-19T09:54:44Z

Allowing -C target-feature=-outline-atomics to override this setting would definitely be an improvement, but it would not work because the std library would still be compiled with it enabled.

But I can move the outline atomics block before -C target-feature processing code as well (later feature specs override earlier ones).

hkratz · 2021-11-04T11:40:25Z

If an updated libc with rust-lang/libc#2272 fixes it, then this is no longer needed. Let's wait for that.

@rustbot label -S-waiting-on-review +S-waiting-on-author

jbg · 2021-11-04T12:00:05Z

This issue does not only occur with a libc dependency in the tree. Even a no-deps Hello World program triggers it.

hkratz · 2021-11-04T15:02:03Z

This issue does not only occur with a libc dependency in the tree. Even a no-deps Hello World program triggers it.

Yes, but the std library uses rust-lang/libc. Having an unbundled libc.a at the right place in link order will resolve this problem as well.

workingjubilee · 2021-11-05T20:31:14Z

😩 Sorry for missing this. Let me see...

workingjubilee · 2021-11-05T21:32:20Z

So it looks like we accidentally broke musl on aarch64 because we aren't compiling musl in a way that is convenient for musl (already a known factor, really, but I didn't expect it to cause an issue here), and:

we may find out that a recent libc crate update fixes it when it lands
but we should try to get this resolved before it hits stable
and another PR against rust-lang/rust offers a known permanent fix Eventually

so this one should wait a little for that but not a long time, correct? Alright, I will keep this on my radar.

workingjubilee · 2021-11-05T21:42:20Z

Speaking of radar, it looks like we bumped LLVM to min 12. Accordingly, #90623 was opened, which remedies the FIXME and also will pose a merge conflict with this PR.

I would stop the rollup, but currently we seem to be inclined to let things ride for a few nights and hope a new libc fixes it, so might as well let it ride. It also addresses the second commit in this set.

bors · 2021-11-06T01:35:55Z

☔ The latest upstream changes (presumably #90631) made this pull request unmergeable. Please resolve the merge conflicts.

hkratz · 2021-11-06T19:08:07Z

If the libc update does not fix it, I will update this PR to just remove the +outline-atomics feature from the aarch64_unknown_linux_musl target spec.

Changelog: https://github.com/rust-lang/libc/releases/tag/0.2.107 Primarily intended to pull in rust-lang/libc#2272 This should help with rust-lang#90044

Changelog: https://github.com/rust-lang/libc/releases/tag/0.2.107 Primarily intended to pull in fd331f65f214ea75b6210b415b5fd8650be15c73 This should help with rust-lang#90044

…itor Update libc to 0.2.107 Changelog: https://github.com/rust-lang/libc/releases/tag/0.2.107 Primarily intended to pull in rust-lang/libc@fd331f6 This should help with rust-lang#90044

Update libc to 0.2.107 Changelog: https://github.com/rust-lang/libc/releases/tag/0.2.107 Primarily intended to pull in rust-lang/libc@fd331f6 This should help with rust-lang#90044

The introduced dependency on `getauxval`causes linking problems with musl, see rust-lang#89626.

Changelog: https://github.com/rust-lang/libc/releases/tag/0.2.107 https://github.com/rust-lang/libc/releases/tag/0.2.108 Primarily intended to pull in fd331f65f214ea75b6210b415b5fd8650be15c73 This should help with rust-lang#90044

hkratz · 2021-11-24T16:34:40Z

Damn, this can't be backported to beta as #90623 (on which this builds now) was after the beta fork.

workingjubilee · 2021-11-24T16:47:06Z

Whoops, didn't notice that this got updated, sorry. Unfortunately didn't find time to push through the libc cascade all the way, so it looks like this will be it for now. We can figure out if #90681 will fix it on the next train, when we have the luxury of time.
This looks correct.

workingjubilee · 2021-11-24T16:47:53Z

Ah damn.

workingjubilee · 2021-11-24T16:58:13Z

@pnkfelix It seems this PR can't land on beta, but I agree with Hans' remarks on Zulip regarding the severity of the regression. I have no idea how we should proceed in terms of mitigation.

Brainstorming alternatives in full-on "throw spaghetti at wall" mode:

Technically #90681 might fix it if merged and then backported but that seems risky as it pulls in even more diffs, which would be fine on nightly but to push into beta would involve even more risks of regressions. That would also require #90527
hack in one of the known mitigations for now, like defaulting to using lld for that target for a cycle??? seems also risky.
cry and allow the target to regress :( strictly speaking, this is (probably?) permitted by our aarch64-linux-musl platform support policy, as it is tier 2 and thus we do not have the solidity of the tier 1 "yes, it always works" policies, but it seems a bit strained since it always is supposed to build.

hkratz · 2021-11-24T17:09:43Z

I can open a minimal, functionally equivalent PR against beta (just restricting aarch64 outline atomics to glibc) and test that thoroughly. But I don't know if policy allows (non-backport) PRs that land only in beta.

workingjubilee · 2021-11-24T17:11:59Z

Sometimes we do point releases, so I can't imagine it's completely banned? I am not familiar with that nuance, however.

workingjubilee · 2021-11-24T17:43:09Z

Though, speaking of host tools guarantees:
How did the original regression land if this issue blocks even linking a simple "Hello, world!"?

workingjubilee · 2021-11-24T20:04:51Z

I find this state of affairs baffling but I am going to approve this commit with a note here that it can't actually be backported in as-is form, so that this issue doesn't persist into the next beta cut.
@bors r+ rollup=always

bors · 2021-11-24T20:04:53Z

📌 Commit bd287fa has been approved by workingjubilee

…mics_for_musl, r=workingjubilee Restrict aarch64 outline atomics to glibc for now. The introduced dependency on `getauxval` causes linking problems with musl, making compiling any binaries for `aarch64-unknown-linux-musl` impossible without workarounds such as using lld or adding liblibc.rlib again to the linker invocation, see rust-lang#89626. This is a workaround until libc>0.2.108 is merged.

…laumeGomez Rollup of 7 pull requests Successful merges: - rust-lang#89542 (Partially stabilize `duration_consts_2`) - rust-lang#90044 (Restrict aarch64 outline atomics to glibc for now.) - rust-lang#90420 (Create rustdoc_internals feature gate) - rust-lang#91075 (Reduce prominence of item-infos) - rust-lang#91151 (Fix test in std::process on android) - rust-lang#91179 (Fix more <a> color) - rust-lang#91199 (rustdoc: Add test for mixing doc comments and attrs) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

rust-highfive assigned oli-obk Oct 19, 2021

rust-highfive added the S-waiting-on-review label Oct 19, 2021

rust-highfive assigned workingjubilee and unassigned oli-obk Oct 19, 2021

tonyg mentioned this pull request Oct 20, 2021

aarch64 builds using nightly fail with missing getauxval in init_have_lse_atomics in cpu_model.c in compiler_builtins rust-embedded/cross#598

Closed

apiraino added the T-compiler label Oct 28, 2021

rustbot added S-waiting-on-author and removed S-waiting-on-review labels Nov 4, 2021

workingjubilee mentioned this pull request Nov 5, 2021

Bump libc to 0.2.107 rust-lang/libc#2515

Merged

bors closed this in cd5de2f Nov 7, 2021

workingjubilee reopened this Nov 8, 2021

workingjubilee added a commit to workingjubilee/rustc that referenced this issue Nov 8, 2021

Update libc to 0.2.107

597bfa3

Changelog: https://github.com/rust-lang/libc/releases/tag/0.2.107 Primarily intended to pull in rust-lang/libc#2272 This should help with rust-lang#90044

workingjubilee mentioned this pull request Nov 8, 2021

Update libc to 0.2.108 #90681

Open

Disable aarch64 outline atomics with musl for now.

bd287fa

The introduced dependency on `getauxval`causes linking problems with musl, see rust-lang#89626.

hkratz force-pushed the disable_arm_outline_atomics_for_musl branch from 9c7500e to bd287fa Nov 10, 2021

pnkfelix added the beta-nominated label Nov 24, 2021

bors added S-waiting-on-bors and removed S-waiting-on-author labels Nov 24, 2021

GuillaumeGomez mentioned this pull request Nov 24, 2021

Rollup of 8 pull requests #91198

Closed

GuillaumeGomez mentioned this pull request Nov 24, 2021

Rollup of 7 pull requests #91202

Closed

GuillaumeGomez mentioned this pull request Nov 24, 2021

Rollup of 7 pull requests #91203

Merged

bors merged commit cbe563a into rust-lang:master Nov 25, 2021
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rust-lang / rust Public

Restrict aarch64 outline atomics to glibc for now. #90044

Restrict aarch64 outline atomics to glibc for now. #90044

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rust-lang / rust Public

Restrict aarch64 outline atomics to glibc for now. #90044

Restrict aarch64 outline atomics to glibc for now. #90044

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