Merge 216da0b7 (automated)

1 files changed, 55 insertions, 0 deletions

diff --git a/pkg/sentry/time/seqatomic_parameters.go b/pkg/sentry/time/seqatomic_parameters.go
new file mode 100755
index 000000000..ecbea4d94
--- /dev/null
+++ b/pkg/sentry/time/seqatomic_parameters.go
@@ -0,0 +1,55 @@
+package time
+
+import (
+	"reflect"
+	"strings"
+	"unsafe"
+
+	"fmt"
+	"gvisor.googlesource.com/gvisor/third_party/gvsync"
+)
+
+// SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
+// with any writer critical sections in sc.
+func SeqAtomicLoadParameters(sc *gvsync.SeqCount, ptr *Parameters) Parameters {
+	// This function doesn't use SeqAtomicTryLoad because doing so is
+	// measurably, significantly (~20%) slower; Go is awful at inlining.
+	var val Parameters
+	for {
+		epoch := sc.BeginRead()
+		if gvsync.RaceEnabled {
+
+			gvsync.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val))
+		} else {
+
+			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 SeqAtomicTryLoadParameters(sc *gvsync.SeqCount, epoch gvsync.SeqCountEpoch, ptr *Parameters) (Parameters, bool) {
+	var val Parameters
+	if gvsync.RaceEnabled {
+		gvsync.Memmove(unsafe.Pointer(&val), unsafe.Pointer(ptr), unsafe.Sizeof(val))
+	} else {
+		val = *ptr
+	}
+	return val, sc.ReadOk(epoch)
+}
+
+func initParameters() {
+	var val Parameters
+	typ := reflect.TypeOf(val)
+	name := typ.Name()
+	if ptrs := gvsync.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")))
+	}
+}