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.

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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: Dec 23 2024 at 13:07 UTC