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runtime: execute publicationBarrier in noscan case for delayed zeroing

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This is a peace-of-mind change to make sure that delayed-zeroed memory
(in the large alloc case) is globally visible from the moment the
allocation is published back to the caller.

The way it's written right now is good enough for the garbage collector
(we already have a publication barrier for a nil span.largeType, so the
GC will ignore the noscan span) but this might matter for user code on
weak memory architectures.

Change-Id: I06ac9b95863074e5f09382629083b19bfa87fdb8
Reviewed-on: https://go-review.googlesource.com/c/go/+/619036
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Michael Anthony Knyszek 2024-10-09 17:38:49 +00:00 committed by Gopher Robot
parent a1c4fb4361
commit acd072a078
1 changed files with 4 additions and 5 deletions
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9
src/runtime/malloc.go
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@ -1581,14 +1581,13 @@ func mallocgcLarge(size uintptr, typ *_type, needzero bool) (unsafe.Pointer, uin
memclrNoHeapPointersChunked(size, x) // This is a possible preemption point: see #47302
// Finish storing the type information for this case.
mp := acquirem()
if !noscan {
mp := acquirem()
getMCache(mp).scanAlloc += heapSetTypeLarge(uintptr(x), size, typ, span)
// Publish the type information with the zeroed memory.
publicationBarrier()
releasem(mp)
}
// Publish the object with the now-zeroed memory.
publicationBarrier()
releasem(mp)
}
return x, size
}