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Explain why it's safe to allocate chans with flagNoScan.

LGTM=rsc
R=golang-codereviews
CC=golang-codereviews, khr, rsc
https://golang.org/cl/125510045
This commit is contained in:
Dmitriy Vyukov 2014-08-25 20:26:32 +04:00
parent 9601abaf8b
commit 4064d5e9a3
1 changed files with 5 additions and 1 deletions
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6
src/pkg/runtime/chan.go
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@ -33,7 +33,11 @@ func makechan(t *chantype, size int64) *hchan {
var c *hchan var c *hchan
if elem.kind&kindNoPointers != 0 || size == 0 { if elem.kind&kindNoPointers != 0 || size == 0 {
// allocate memory in one call // Allocate memory in one call.
// Hchan does not contain pointers interesting for GC in this case:
// buf points into the same allocation, elemtype is persistent
// and SudoG's are referenced from G so can't be collected.
// TODO(dvyukov,rlh): Rethink when collector can move allocated objects.
c = (*hchan)(gomallocgc(hchanSize+uintptr(size)*uintptr(elem.size), nil, flagNoScan)) c = (*hchan)(gomallocgc(hchanSize+uintptr(size)*uintptr(elem.size), nil, flagNoScan))
if size > 0 && elem.size != 0 { if size > 0 && elem.size != 0 {
c.buf = (*uint8)(add(unsafe.Pointer(c), hchanSize)) c.buf = (*uint8)(add(unsafe.Pointer(c), hchanSize))