github.com/c0deoo1/golang1.5@v0.0.0-20220525150107-c87c805d4593/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 "unsafe"
     8  
     9  // These functions cannot have go:noescape annotations,
    10  // because while ptr does not escape, new does.
    11  // If new is marked as not escaping, the compiler will make incorrect
    12  // escape analysis decisions about the pointer value being stored.
    13  // Instead, these are wrappers around the actual atomics (xchgp1 and so on)
    14  // that use noescape to convey which arguments do not escape.
    15  //
    16  // Additionally, these functions must update the shadow heap for
    17  // write barrier checking.
    18  
    19  //go:nosplit
    20  func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
    21  	atomicstorep1(noescape(ptr), new)
    22  	writebarrierptr_nostore((*uintptr)(ptr), uintptr(new))
    23  }
    24  
    25  //go:nosplit
    26  func xchgp(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer {
    27  	old := xchgp1(noescape(ptr), new)
    28  	writebarrierptr_nostore((*uintptr)(ptr), uintptr(new))
    29  	return old
    30  }
    31  
    32  //go:nosplit
    33  func casp(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
    34  	if !casp1((*unsafe.Pointer)(noescape(unsafe.Pointer(ptr))), noescape(old), new) {
    35  		return false
    36  	}
    37  	writebarrierptr_nostore((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
    38  	return true
    39  }
    40  
    41  // Like above, but implement in terms of sync/atomic's uintptr operations.
    42  // We cannot just call the runtime routines, because the race detector expects
    43  // to be able to intercept the sync/atomic forms but not the runtime forms.
    44  
    45  //go:linkname sync_atomic_StoreUintptr sync/atomic.StoreUintptr
    46  func sync_atomic_StoreUintptr(ptr *uintptr, new uintptr)
    47  
    48  //go:linkname sync_atomic_StorePointer sync/atomic.StorePointer
    49  //go:nosplit
    50  func sync_atomic_StorePointer(ptr *unsafe.Pointer, new unsafe.Pointer) {
    51  	sync_atomic_StoreUintptr((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
    52  	atomicstorep1(noescape(unsafe.Pointer(ptr)), new)
    53  	writebarrierptr_nostore((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
    54  }
    55  
    56  //go:linkname sync_atomic_SwapUintptr sync/atomic.SwapUintptr
    57  func sync_atomic_SwapUintptr(ptr *uintptr, new uintptr) uintptr
    58  
    59  //go:linkname sync_atomic_SwapPointer sync/atomic.SwapPointer
    60  //go:nosplit
    61  func sync_atomic_SwapPointer(ptr unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer {
    62  	old := unsafe.Pointer(sync_atomic_SwapUintptr((*uintptr)(noescape(ptr)), uintptr(new)))
    63  	writebarrierptr_nostore((*uintptr)(ptr), uintptr(new))
    64  	return old
    65  }
    66  
    67  //go:linkname sync_atomic_CompareAndSwapUintptr sync/atomic.CompareAndSwapUintptr
    68  func sync_atomic_CompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
    69  
    70  //go:linkname sync_atomic_CompareAndSwapPointer sync/atomic.CompareAndSwapPointer
    71  //go:nosplit
    72  func sync_atomic_CompareAndSwapPointer(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
    73  	if !sync_atomic_CompareAndSwapUintptr((*uintptr)(noescape(unsafe.Pointer(ptr))), uintptr(old), uintptr(new)) {
    74  		return false
    75  	}
    76  	writebarrierptr_nostore((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
    77  	return true
    78  }