net: work around runtime scheduler starvation on js and wasip1

Fixes #65177.
Updates #65178.
Updates #64321.

Change-Id: I698fd3b688c7dfbde692eb7c29cbdafc89e7ca32
Cq-Include-Trybots: luci.golang.try:gotip-js-wasm,gotip-wasip1-wasm_wasmtime,gotip-wasip1-wasm_wazero
Reviewed-on: https://go-review.googlesource.com/c/go/+/557037
Auto-Submit: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>

Author: Bryan C. Mills

src/net/net_fake.go

@@ -14,6 +14,7 @@ import (
 	"errors"
 	"io"
 	"os"
+	"runtime"
 	"sync"
 	"sync/atomic"
 	"syscall"
@@ -513,6 +514,15 @@ func (pq *packetQueue) send(dt *deadlineTimer, b []byte, from sockaddr, block bo
 	if !block {
 		full = pq.full
 	}
+
+	// Before we check dt.expired, yield to other goroutines.
+	// This may help to prevent starvation of the goroutine that runs the
+	// deadlineTimer's time.After callback.
+	//
+	// TODO(#65178): Remove this when the runtime scheduler no longer starves
+	// runnable goroutines.
+	runtime.Gosched()
+
 	select {
 	case <-dt.expired:
 		return 0, os.ErrDeadlineExceeded
@@ -563,6 +573,15 @@ func (pq *packetQueue) recvfrom(dt *deadlineTimer, b []byte, wholePacket bool, c
 		// (Without this, TestZeroByteRead deadlocks.)
 		empty = pq.empty
 	}
+
+	// Before we check dt.expired, yield to other goroutines.
+	// This may help to prevent starvation of the goroutine that runs the
+	// deadlineTimer's time.After callback.
+	//
+	// TODO(#65178): Remove this when the runtime scheduler no longer starves
+	// runnable goroutines.
+	runtime.Gosched()
+
 	select {
 	case <-dt.expired:
 		return 0, nil, os.ErrDeadlineExceeded