diff --git a/src/runtime/chan.go b/src/runtime/chan.go
index c953b23..1d4599e 100644
--- a/src/runtime/chan.go
+++ b/src/runtime/chan.go
@@ -121,6 +121,21 @@
 	return add(c.buf, uintptr(i)*uintptr(c.elemsize))
 }
 
+// full reports whether a send on c would block (that is, the channel is full).
+// It uses a single word-sized read of mutable state, so although
+// the answer is instantaneously true, the correct answer may have changed
+// by the time the calling function receives the return value.
+func full(c *hchan) bool {
+	// c.dataqsiz is immutable (never written after the channel is created)
+	// so it is safe to read at any time during channel operation.
+	if c.dataqsiz == 0 {
+		// Assumes that a pointer read is relaxed-atomic.
+		return c.recvq.first == nil
+	}
+	// Assumes that a uint read is relaxed-atomic.
+	return c.qcount == c.dataqsiz
+}
+
 // entry point for c <- x from compiled code
 //go:nosplit
 func chansend1(c *hchan, elem unsafe.Pointer) {
@@ -160,7 +175,7 @@
 	//
 	// After observing that the channel is not closed, we observe that the channel is
 	// not ready for sending. Each of these observations is a single word-sized read
-	// (first c.closed and second c.recvq.first or c.qcount depending on kind of channel).
+	// (first c.closed and second full()).
 	// Because a closed channel cannot transition from 'ready for sending' to
 	// 'not ready for sending', even if the channel is closed between the two observations,
 	// they imply a moment between the two when the channel was both not yet closed
@@ -169,9 +184,10 @@
 	//
 	// It is okay if the reads are reordered here: if we observe that the channel is not
 	// ready for sending and then observe that it is not closed, that implies that the
-	// channel wasn't closed during the first observation.
-	if !block && c.closed == 0 && ((c.dataqsiz == 0 && c.recvq.first == nil) ||
-		(c.dataqsiz > 0 && c.qcount == c.dataqsiz)) {
+	// channel wasn't closed during the first observation. However, nothing here
+	// guarantees forward progress. We rely on the side effects of lock release in
+	// chanrecv() and closechan() to update this thread's view of c.closed and full().
+	if !block && c.closed == 0 && full(c) {
 		return false
 	}
 
@@ -401,6 +417,16 @@
 	}
 }
 
+// empty reports whether a read from c would block (that is, the channel is
+// empty).  It uses a single atomic read of mutable state.
+func empty(c *hchan) bool {
+	// c.dataqsiz is immutable.
+	if c.dataqsiz == 0 {
+		return atomic.Loadp(unsafe.Pointer(&c.sendq.first)) == nil
+	}
+	return atomic.Loaduint(&c.qcount) == 0
+}
+
 // entry points for <- c from compiled code
 //go:nosplit
 func chanrecv1(c *hchan, elem unsafe.Pointer) {
@@ -436,21 +462,36 @@
 	}
 
 	// Fast path: check for failed non-blocking operation without acquiring the lock.
-	//
-	// After observing that the channel is not ready for receiving, we observe that the
-	// channel is not closed. Each of these observations is a single word-sized read
-	// (first c.sendq.first or c.qcount, and second c.closed).
-	// Because a channel cannot be reopened, the later observation of the channel
-	// being not closed implies that it was also not closed at the moment of the
-	// first observation. We behave as if we observed the channel at that moment
-	// and report that the receive cannot proceed.
-	//
-	// The order of operations is important here: reversing the operations can lead to
-	// incorrect behavior when racing with a close.
-	if !block && (c.dataqsiz == 0 && c.sendq.first == nil ||
-		c.dataqsiz > 0 && atomic.Loaduint(&c.qcount) == 0) &&
-		atomic.Load(&c.closed) == 0 {
-		return
+	if !block && empty(c) {
+		// After observing that the channel is not ready for receiving, we observe whether the
+		// channel is closed.
+		//
+		// Reordering of these checks could lead to incorrect behavior when racing with a close.
+		// For example, if the channel was open and not empty, was closed, and then drained,
+		// reordered reads could incorrectly indicate "open and empty". To prevent reordering,
+		// we use atomic loads for both checks, and rely on emptying and closing to happen in
+		// separate critical sections under the same lock.  This assumption fails when closing
+		// an unbuffered channel with a blocked send, but that is an error condition anyway.
+		if atomic.Load(&c.closed) == 0 {
+			// Because a channel cannot be reopened, the later observation of the channel
+			// being not closed implies that it was also not closed at the moment of the
+			// first observation. We behave as if we observed the channel at that moment
+			// and report that the receive cannot proceed.
+			return
+		}
+		// The channel is irreversibly closed. Re-check whether the channel has any pending data
+		// to receive, which could have arrived between the empty and closed checks above.
+		// Sequential consistency is also required here, when racing with such a send.
+		if empty(c) {
+			// The channel is irreversibly closed and empty.
+			if raceenabled {
+				raceacquire(c.raceaddr())
+			}
+			if ep != nil {
+				typedmemclr(c.elemtype, ep)
+			}
+			return true, false
+		}
 	}
 
 	var t0 int64
diff --git a/src/runtime/chan_test.go b/src/runtime/chan_test.go
index 1180e76..039a086 100644
--- a/src/runtime/chan_test.go
+++ b/src/runtime/chan_test.go
@@ -1127,6 +1127,20 @@
 	wg.Wait()
 }
 
+func BenchmarkChanClosed(b *testing.B) {
+	c := make(chan struct{})
+	close(c)
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			select {
+			case <-c:
+			default:
+				b.Error("Unreachable")
+			}
+		}
+	})
+}
+
 var (
 	alwaysFalse = false
 	workSink    = 0