[go] runtime: add race instrumentation for moduleToTypelinksLock

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Cherry Mui (Gerrit)

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Feb 9, 2026, 12:32:19 PMFeb 9

to Chressie Himpel, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Go LUCI, Ian Lance Taylor, golang-co...@googlegroups.com

Cherry Mui submitted the change

Change information

Commit message:

runtime: add race instrumentation for moduleToTypelinksLock

From Cherry Mui on the CL review:

The reason why we need race instrumentation is tricky. The runtime
package is not compiled with race instrumentation, therefore the race
detector doesn't know about synchronizations within the runtime, and
usually it doesn't care, as it also doesn't know about the concurrent
data accesses in the runtime.

However, in this case the concurrent access is in a map. Map accesses
are always instrumented
https://cs.opensource.google/go/go/+/master:src/internal/runtime/maps/runtime_fast64.go;l=25,
even if the map is defined in the runtime. So the race detector does see
the concurrent access. But it doesn't see the synchronization. So this
CL adds them.

Go maps are not common in the runtime. But I recall an issue like this
did occur. Maybe we could make the compiler/runtime not to instrument
map accesses for maps defined in the runtime (which would be a more
involved change).

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The reproducer in src/runtime/testdata/testprog/typelinksrace.go was
provided by Cherry Mui.