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runtime: make mapzero not crash on arm

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Change-Id: I40e8a4a2e62253233b66f6a2e61e222437292c31
Reviewed-on: https://go-review.googlesource.com/10151
Reviewed-by: Minux Ma <minux@golang.org>
This commit is contained in:
Russ Cox 2015-05-15 16:05:52 -04:00
parent ddc4c146a4
commit d820d5f3ab
1 changed files with 12 additions and 0 deletions
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12
src/runtime/hashmap.go
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@ -1008,6 +1008,18 @@ var zerotiny [1024]byte
// Types allocated by package reflect are in writable memory and
// start out with zero set to nil; we initialize those on demand.
func mapzero(t *_type) {
// On ARM, atomicloadp is implemented as xadd(p, 0),
// so we cannot use atomicloadp on read-only memory.
// Check whether the pointer is in the heap; if not, it's not writable
// so the zero value must already be set.
if GOARCH == "arm" && !inheap(uintptr(unsafe.Pointer(t))) {
if t.zero == nil {
print("runtime: map element ", *t._string, " missing zero value\n")
throw("mapzero")
}
return
}
// Already done?
// Check without lock, so must use atomicload to sync with atomicstore in allocation case below.
if atomicloadp(unsafe.Pointer(&t.zero)) != nil {