github.com/miolini/go@v0.0.0-20160405192216-fca68c8cb408/src/runtime/atomic_pointer.go (about) 1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package runtime 6 7 import ( 8 "runtime/internal/atomic" 9 "unsafe" 10 ) 11 12 // These functions cannot have go:noescape annotations, 13 // because while ptr does not escape, new does. 14 // If new is marked as not escaping, the compiler will make incorrect 15 // escape analysis decisions about the pointer value being stored. 16 // Instead, these are wrappers around the actual atomics (casp1 and so on) 17 // that use noescape to convey which arguments do not escape. 18 // 19 // Additionally, these functions must update the shadow heap for 20 // write barrier checking. 21 22 //go:nosplit 23 func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) { 24 atomic.Storep1(noescape(ptr), new) 25 writebarrierptr_nostore((*uintptr)(ptr), uintptr(new)) 26 } 27 28 //go:nosplit 29 func casp(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool { 30 if !atomic.Casp1((*unsafe.Pointer)(noescape(unsafe.Pointer(ptr))), noescape(old), new) { 31 return false 32 } 33 writebarrierptr_nostore((*uintptr)(unsafe.Pointer(ptr)), uintptr(new)) 34 return true 35 } 36 37 // Like above, but implement in terms of sync/atomic's uintptr operations. 38 // We cannot just call the runtime routines, because the race detector expects 39 // to be able to intercept the sync/atomic forms but not the runtime forms. 40 41 //go:linkname sync_atomic_StoreUintptr sync/atomic.StoreUintptr 42 func sync_atomic_StoreUintptr(ptr *uintptr, new uintptr) 43 44 //go:linkname sync_atomic_StorePointer sync/atomic.StorePointer 45 //go:nosplit 46 func sync_atomic_StorePointer(ptr *unsafe.Pointer, new unsafe.Pointer) { 47 sync_atomic_StoreUintptr((*uintptr)(unsafe.Pointer(ptr)), uintptr(new)) 48 atomic.Storep1(noescape(unsafe.Pointer(ptr)), new) 49 writebarrierptr_nostore((*uintptr)(unsafe.Pointer(ptr)), uintptr(new)) 50 } 51 52 //go:linkname sync_atomic_SwapUintptr sync/atomic.SwapUintptr 53 func sync_atomic_SwapUintptr(ptr *uintptr, new uintptr) uintptr 54 55 //go:linkname sync_atomic_SwapPointer sync/atomic.SwapPointer 56 //go:nosplit 57 func sync_atomic_SwapPointer(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer { 58 old := unsafe.Pointer(sync_atomic_SwapUintptr((*uintptr)(noescape(ptr)), uintptr(new))) 59 writebarrierptr_nostore((*uintptr)(ptr), uintptr(new)) 60 return old 61 } 62 63 //go:linkname sync_atomic_CompareAndSwapUintptr sync/atomic.CompareAndSwapUintptr 64 func sync_atomic_CompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool 65 66 //go:linkname sync_atomic_CompareAndSwapPointer sync/atomic.CompareAndSwapPointer 67 //go:nosplit 68 func sync_atomic_CompareAndSwapPointer(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool { 69 if !sync_atomic_CompareAndSwapUintptr((*uintptr)(noescape(unsafe.Pointer(ptr))), uintptr(old), uintptr(new)) { 70 return false 71 } 72 writebarrierptr_nostore((*uintptr)(unsafe.Pointer(ptr)), uintptr(new)) 73 return true 74 }