Stream: git-wasmtime

Topic: wasmtime / PR #2709 Fix some issues around TLS management...

Wasmtime GitHub notifications bot (Mar 05 2021 at 21:57):

alexcrichton opened PR #2709 from manage-tls-better to main:

This commit fixes a few issues around managing the thread-local state of
a wasmtime thread. We intentionally only have a singular TLS variable in
the whole world, and the problem is that when stack-switching off an
async thread we were not restoring the previous TLS state. This is
necessary in two cases:

• Futures aren't guaranteed to be polled/completed in a stack-like
  fashion. If a poll sees that a future isn't ready then we may resume
  execution in a previous wasm context that ends up needing the TLS
  information.

• Futures can also cross threads (when the whole store crosses threads)
  and we need to save/restore TLS state from the thread we're coming
  from and the thread that we're going to.

The stack switching issue necessitates some more glue around suspension
and resumption of a stack to ensure we save/restore the TLS state on
both sides. The thread issue, however, also necessitates that we use
#[inline(never)] on TLS access functions and never have TLS borrows
live across a function which could result in running arbitrary code (as
was the case for the tls::set function.

<!--

Please ensure that the following steps are all taken care of before submitting
the PR.

• [ ] This has been discussed in issue #..., or if not, please tell us why
  here.

• [ ] A short description of what this does, why it is needed; if the
  description becomes long, the matter should probably be discussed in an issue
  first.

• [ ] This PR contains test cases, if meaningful.

• [ ] A reviewer from the core maintainer team has been assigned for this PR.
  If you don't know who could review this, please indicate so. The list of
  suggested reviewers on the right can help you.

Please ensure all communication adheres to the code of conduct.
-->

Wasmtime GitHub notifications bot (Mar 11 2021 at 00:33):

peterhuene submitted PR Review.

Wasmtime GitHub notifications bot (Mar 11 2021 at 16:25):

alexcrichton updated PR #2709 from manage-tls-better to main.

Wasmtime GitHub notifications bot (Mar 11 2021 at 17:32):

alexcrichton merged PR #2709.

Last updated: Nov 22 2024 at 17:03 UTC