diff options
Diffstat (limited to 'pkg/sync/seqatomic_unsafe.go')
-rw-r--r-- | pkg/sync/seqatomic_unsafe.go | 81 |
1 files changed, 0 insertions, 81 deletions
diff --git a/pkg/sync/seqatomic_unsafe.go b/pkg/sync/seqatomic_unsafe.go deleted file mode 100644 index bea31adc5..000000000 --- a/pkg/sync/seqatomic_unsafe.go +++ /dev/null @@ -1,81 +0,0 @@ -// Copyright 2018 Google LLC -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -// Package template doesn't exist. This file must be instantiated using the -// go_template_instance rule in tools/go_generics/defs.bzl. -package template - -import ( - "fmt" - "reflect" - "strings" - "unsafe" - - ssync "gvisor.googlesource.com/gvisor/pkg/sync" -) - -// Value is a required type parameter. -// -// Value must not contain any pointers, including interface objects, function -// objects, slices, maps, channels, unsafe.Pointer, and arrays or structs -// containing any of the above. An init() function will panic if this property -// does not hold. -type Value struct{} - -// SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race -// with any writer critical sections in sc. -func SeqAtomicLoad(sc *ssync.SeqCount, ptr *Value) Value { - // This function doesn't use SeqAtomicTryLoad because doing so is - // measurably, significantly (~20%) slower; Go is awful at inlining. - var val Value - for { - epoch := sc.BeginRead() - if ssync.RaceEnabled { - // runtime.RaceDisable() doesn't actually stop the race detector, - // so it can't help us here. Instead, call runtime.memmove - // directly, which is not instrumented by the race detector. - ssync.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val)) - } else { - // This is ~40% faster for short reads than going through memmove. - val = *ptr - } - if sc.ReadOk(epoch) { - break - } - } - return val -} - -// SeqAtomicTryLoad returns a copy of *ptr while in a reader critical section -// in sc initiated by a call to sc.BeginRead() that returned epoch. If the read -// would race with a writer critical section, SeqAtomicTryLoad returns -// (unspecified, false). -func SeqAtomicTryLoad(sc *ssync.SeqCount, epoch ssync.SeqCountEpoch, ptr *Value) (Value, bool) { - var val Value - if ssync.RaceEnabled { - ssync.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val)) - } else { - val = *ptr - } - return val, sc.ReadOk(epoch) -} - -func init() { - var val Value - typ := reflect.TypeOf(val) - name := typ.Name() - if ptrs := ssync.PointersInType(typ, name); len(ptrs) != 0 { - panic(fmt.Sprintf("SeqAtomicLoad<%s> is invalid since values %s of type %s contain pointers:\n%s", typ, name, typ, strings.Join(ptrs, "\n"))) - } -} |