From 8a45c8161601e62faa0d448ff6d5bc0604ea406f Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Fri, 4 Dec 2020 19:05:08 -0800 Subject: Allow use of SeqAtomic with pointer-containing types. Per runtime.memmove, pointers are always copied atomically, as this is required by the GC. (Also, the init() safety check doesn't work because it gets renamed to init() by template instantiation.) PiperOrigin-RevId: 345800302 --- pkg/sync/seqatomic_unsafe.go | 17 -------------- pkg/sync/seqcount.go | 34 ---------------------------- pkg/sync/seqcount_test.go | 53 -------------------------------------------- 3 files changed, 104 deletions(-) (limited to 'pkg/sync') diff --git a/pkg/sync/seqatomic_unsafe.go b/pkg/sync/seqatomic_unsafe.go index 2184cb5ab..780f3b8f8 100644 --- a/pkg/sync/seqatomic_unsafe.go +++ b/pkg/sync/seqatomic_unsafe.go @@ -8,20 +8,12 @@ package template import ( - "fmt" - "reflect" - "strings" "unsafe" "gvisor.dev/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 @@ -55,12 +47,3 @@ func SeqAtomicTryLoad(seq *sync.SeqCount, epoch sync.SeqCountEpoch, ptr *Value) ok = seq.ReadOk(epoch) return } - -func init() { - var val Value - typ := reflect.TypeOf(val) - name := typ.Name() - if ptrs := sync.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"))) - } -} diff --git a/pkg/sync/seqcount.go b/pkg/sync/seqcount.go index 2c5d3df99..1f025f33c 100644 --- a/pkg/sync/seqcount.go +++ b/pkg/sync/seqcount.go @@ -6,8 +6,6 @@ package sync import ( - "fmt" - "reflect" "sync/atomic" ) @@ -27,9 +25,6 @@ import ( // - SeqCount may be more flexible: correct use of SeqCount.ReadOk allows other // operations to be made atomic with reads of SeqCount-protected data. // -// - SeqCount may be less flexible: as of this writing, SeqCount-protected data -// cannot include pointers. -// // - SeqCount is more cumbersome to use; atomic reads of SeqCount-protected // data require instantiating function templates using go_generics (see // seqatomic.go). @@ -128,32 +123,3 @@ func (s *SeqCount) EndWrite() { panic("SeqCount.EndWrite outside writer critical section") } } - -// PointersInType returns a list of pointers reachable from values named -// valName of the given type. -// -// PointersInType is not exhaustive, but it is guaranteed that if typ contains -// at least one pointer, then PointersInTypeOf returns a non-empty list. -func PointersInType(typ reflect.Type, valName string) []string { - switch kind := typ.Kind(); kind { - case reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128: - return nil - - case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice, reflect.String, reflect.UnsafePointer: - return []string{valName} - - case reflect.Array: - return PointersInType(typ.Elem(), valName+"[]") - - case reflect.Struct: - var ptrs []string - for i, n := 0, typ.NumField(); i < n; i++ { - field := typ.Field(i) - ptrs = append(ptrs, PointersInType(field.Type, fmt.Sprintf("%s.%s", valName, field.Name))...) - } - return ptrs - - default: - return []string{fmt.Sprintf("%s (of type %s with unknown kind %s)", valName, typ, kind)} - } -} diff --git a/pkg/sync/seqcount_test.go b/pkg/sync/seqcount_test.go index 6eb7b4b59..3f5592e3e 100644 --- a/pkg/sync/seqcount_test.go +++ b/pkg/sync/seqcount_test.go @@ -6,7 +6,6 @@ package sync import ( - "reflect" "testing" "time" ) @@ -99,55 +98,3 @@ func BenchmarkSeqCountReadUncontended(b *testing.B) { } }) } - -func TestPointersInType(t *testing.T) { - for _, test := range []struct { - name string // used for both test and value name - val interface{} - ptrs []string - }{ - { - name: "EmptyStruct", - val: struct{}{}, - }, - { - name: "Int", - val: int(0), - }, - { - name: "MixedStruct", - val: struct { - b bool - I int - ExportedPtr *struct{} - unexportedPtr *struct{} - arr [2]int - ptrArr [2]*int - nestedStruct struct { - nestedNonptr int - nestedPtr *int - } - structArr [1]struct { - nonptr int - ptr *int - } - }{}, - ptrs: []string{ - "MixedStruct.ExportedPtr", - "MixedStruct.unexportedPtr", - "MixedStruct.ptrArr[]", - "MixedStruct.nestedStruct.nestedPtr", - "MixedStruct.structArr[].ptr", - }, - }, - } { - t.Run(test.name, func(t *testing.T) { - typ := reflect.TypeOf(test.val) - ptrs := PointersInType(typ, test.name) - t.Logf("Found pointers: %v", ptrs) - if (len(ptrs) != 0 || len(test.ptrs) != 0) && !reflect.DeepEqual(ptrs, test.ptrs) { - t.Errorf("Got %v, wanted %v", ptrs, test.ptrs) - } - }) - } -} -- cgit v1.2.3