golang atomic_pointer 代码
文件路径：/src/runtime/atomic_pointer.go
/ Copyright 2009 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package runtime
import (
"runtime/internal/atomic"
"unsafe"
)
/ These functions cannot have go:noescape annotations,
/ because while ptr does not escape, new does.
/ If new is marked as not escaping, the compiler will make incorrect
/ escape analysis decisions about the pointer value being stored.
/ atomicwb performs a write barrier before an atomic pointer write.
/ The caller should guard the call with "if writeBarrier.enabled".
/
/go:nosplit
func atomicwb(ptr *unsafe.Pointer, new unsafe.Pointer) {
slot := (*uintptr)(unsafe.Pointer(ptr))
if !getg().m.p.ptr().wbBuf.putFast(*slot, uintptr(new)) {
wbBufFlush(slot, uintptr(new))
}
}
/ atomicstorep performs *ptr = new atomically and invokes a write barrier.
/
/go:nosplit
func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
if writeBarrier.enabled {
atomicwb((*unsafe.Pointer)(ptr), new)
}
atomic.StorepNoWB(noescape(ptr), new)
}
/ Like above, but implement in terms of sync/atomic's uintptr operations.
/ We cannot just call the runtime routines, because the race detector expects
/ to be able to intercept the sync/atomic forms but not the runtime forms.
/go:linkname sync_atomic_StoreUintptr sync/atomic.StoreUintptr
func sync_atomic_StoreUintptr(ptr *uintptr, new uintptr)
/go:linkname sync_atomic_StorePointer sync/atomic.StorePointer
/go:nosplit
func sync_atomic_StorePointer(ptr *unsafe.Pointer, new unsafe.Pointer) {
if writeBarrier.enabled {
atomicwb(ptr, new)
}
sync_atomic_StoreUintptr((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
}
/go:linkname sync_atomic_SwapUintptr sync/atomic.SwapUintptr
func sync_atomic_SwapUintptr(ptr *uintptr, new uintptr) uintptr
/go:linkname sync_atomic_SwapPointer sync/atomic.SwapPointer
/go:nosplit
func sync_atomic_SwapPointer(ptr *unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer {
if writeBarrier.enabled {
atomicwb(ptr, new)
}
old := unsafe.Pointer(sync_atomic_SwapUintptr((*uintptr)(noescape(unsafe.Pointer(ptr))), uintptr(new)))
return old
}
/go:linkname sync_atomic_CompareAndSwapUintptr sync/atomic.CompareAndSwapUintptr
func sync_atomic_CompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
/go:linkname sync_atomic_CompareAndSwapPointer sync/atomic.CompareAndSwapPointer
/go:nosplit
func sync_atomic_CompareAndSwapPointer(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
if writeBarrier.enabled {
atomicwb(ptr, new)
}
return sync_atomic_CompareAndSwapUintptr((*uintptr)(noescape(unsafe.Pointer(ptr))), uintptr(old), uintptr(new))
}