runtime: convert schedt.pollUntil to atomic type

Note that this converts pollUntil from uint64 to int64, the type used by
nanotime().

For #53821.

Change-Id: Iec9ec7e09d3350552561d0708ba6ea9e8a8ae7ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/419443
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/align_runtime_test.go

@@ -17,7 +17,6 @@ var AtomicFields = []uintptr{
 	unsafe.Offsetof(p{}.timer0When),
 	unsafe.Offsetof(p{}.timerModifiedEarliest),
 	unsafe.Offsetof(p{}.gcFractionalMarkTime),
-	unsafe.Offsetof(schedt{}.pollUntil),
 	unsafe.Offsetof(schedt{}.timeToRun),
 	unsafe.Offsetof(timeHistogram{}.underflow),
 	unsafe.Offsetof(profBuf{}.overflow),

src/runtime/proc.go

@@ -2804,7 +2804,7 @@ top:
 
 	// Poll network until next timer.
 	if netpollinited() && (atomic.Load(&netpollWaiters) > 0 || pollUntil != 0) && sched.lastpoll.Swap(0) != 0 {
-		atomic.Store64(&sched.pollUntil, uint64(pollUntil))
+		sched.pollUntil.Store(pollUntil)
 		if mp.p != 0 {
 			throw("findrunnable: netpoll with p")
 		}
@@ -2825,7 +2825,7 @@ top:
 			delay = 0
 		}
 		list := netpoll(delay) // block until new work is available
-		atomic.Store64(&sched.pollUntil, 0)
+		sched.pollUntil.Store(0)
 		sched.lastpoll.Store(now)
 		if faketime != 0 && list.empty() {
 			// Using fake time and nothing is ready; stop M.
@@ -2856,7 +2856,7 @@ top:
 			goto top
 		}
 	} else if pollUntil != 0 && netpollinited() {
-		pollerPollUntil := int64(atomic.Load64(&sched.pollUntil))
+		pollerPollUntil := sched.pollUntil.Load()
 		if pollerPollUntil == 0 || pollerPollUntil > pollUntil {
 			netpollBreak()
 		}
@@ -3071,7 +3071,7 @@ func wakeNetPoller(when int64) {
 		// field is either zero or the time to which the current
 		// poll is expected to run. This can have a spurious wakeup
 		// but should never miss a wakeup.
-		pollerPollUntil := int64(atomic.Load64(&sched.pollUntil))
+		pollerPollUntil := sched.pollUntil.Load()
 		if pollerPollUntil == 0 || pollerPollUntil > when {
 			netpollBreak()
 		}

src/runtime/runtime2.go

@@ -758,10 +758,9 @@ type p struct {
 }
 
 type schedt struct {
-	// accessed atomically. keep at top to ensure alignment on 32-bit systems.
 	goidgen   atomic.Uint64
 	lastpoll  atomic.Int64 // time of last network poll, 0 if currently polling
-	pollUntil uint64 // time to which current poll is sleeping
+	pollUntil atomic.Int64 // time to which current poll is sleeping
 
 	lock mutex