runtime: change netpoll to take an amount of time to block

This new facility will be used by future CLs in this series.

Change the only blocking call to netpoll to do the right thing when
netpoll returns an empty list.

Updates #6239
Updates #27707

Change-Id: I58b3c2903eda61a3698b1a4729ed0e81382bb1ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/171821
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

src/runtime/defs1_solaris_amd64.go

@@ -8,6 +8,7 @@ const (
 	_EBADF       = 0x9
 	_EFAULT      = 0xe
 	_EAGAIN      = 0xb
+	_ETIME       = 0x3e
 	_ETIMEDOUT   = 0x91
 	_EWOULDBLOCK = 0xb
 	_EINPROGRESS = 0x96

src/runtime/defs_solaris.go

@@ -38,6 +38,7 @@ const (
 	EBADF       = C.EBADF
 	EFAULT      = C.EFAULT
 	EAGAIN      = C.EAGAIN
+	ETIME       = C.ETIME
 	ETIMEDOUT   = C.ETIMEDOUT
 	EWOULDBLOCK = C.EWOULDBLOCK
 	EINPROGRESS = C.EINPROGRESS

src/runtime/netpoll_aix.go

@@ -148,12 +148,27 @@ func netpollarm(pd *pollDesc, mode int) {
 	unlock(&mtxset)
 }
 
+// netpoll checks for ready network connections.
+// Returns list of goroutines that become runnable.
+// delay < 0: blocks indefinitely
+// delay == 0: does not block, just polls
+// delay > 0: block for up to that many nanoseconds
 //go:nowritebarrierrec
-func netpoll(block bool) gList {
-	timeout := ^uintptr(0)
-	if !block {
-		timeout = 0
+func netpoll(delay int64) gList {
+	var timeout uintptr
+	if delay < 0 {
+		timeout = ^uintptr(0)
+	} else if delay == 0 {
+		// TODO: call poll with timeout == 0
 		return gList{}
+	} else if delay < 1e6 {
+		timeout = 1
+	} else if delay < 1e15 {
+		timeout = uintptr(delay / 1e6)
+	} else {
+		// An arbitrary cap on how long to wait for a timer.
+		// 1e9 ms == ~11.5 days.
+		timeout = 1e9
 	}
 retry:
 	lock(&mtxpoll)
@@ -168,6 +183,11 @@ retry:
 			throw("poll failed")
 		}
 		unlock(&mtxset)
+		// If a timed sleep was interrupted, just return to
+		// recalculate how long we should sleep now.
+		if timeout > 0 {
+			return gList{}
+		}
 		goto retry
 	}
 	// Check if some descriptors need to be changed
@@ -203,8 +223,5 @@ retry:
 		}
 	}
 	unlock(&mtxset)
-	if block && toRun.empty() {
-		goto retry
-	}
 	return toRun
 }

src/runtime/netpoll_epoll.go

@@ -56,15 +56,28 @@ func netpollarm(pd *pollDesc, mode int) {
 	throw("runtime: unused")
 }
 
-// polls for ready network connections
-// returns list of goroutines that become runnable
-func netpoll(block bool) gList {
+// netpoll checks for ready network connections.
+// Returns list of goroutines that become runnable.
+// delay < 0: blocks indefinitely
+// delay == 0: does not block, just polls
+// delay > 0: block for up to that many nanoseconds
+func netpoll(delay int64) gList {
 	if epfd == -1 {
 		return gList{}
 	}
-	waitms := int32(-1)
-	if !block {
+	var waitms int32
+	if delay < 0 {
+		waitms = -1
+	} else if delay == 0 {
 		waitms = 0
+	} else if delay < 1e6 {
+		waitms = 1
+	} else if delay < 1e15 {
+		waitms = int32(delay / 1e6)
+	} else {
+		// An arbitrary cap on how long to wait for a timer.
+		// 1e9 ms == ~11.5 days.
+		waitms = 1e9
 	}
 	var events [128]epollevent
 retry:
@@ -74,6 +87,11 @@ retry:
 			println("runtime: epollwait on fd", epfd, "failed with", -n)
 			throw("runtime: netpoll failed")
 		}
+		// If a timed sleep was interrupted, just return to
+		// recalculate how long we should sleep now.
+		if waitms > 0 {
+			return gList{}
+		}
 		goto retry
 	}
 	var toRun gList
@@ -98,8 +116,5 @@ retry:
 			netpollready(&toRun, pd, mode)
 		}
 	}
-	if block && toRun.empty() {
-		goto retry
-	}
 	return toRun
 }

src/runtime/netpoll_fake.go

@@ -27,6 +27,6 @@ func netpollclose(fd uintptr) int32 {
 func netpollarm(pd *pollDesc, mode int) {
 }
 
-func netpoll(block bool) gList {
+func netpoll(delay int64) gList {
 	return gList{}
 }

src/runtime/netpoll_kqueue.go

@@ -57,15 +57,27 @@ func netpollarm(pd *pollDesc, mode int) {
 	throw("runtime: unused")
 }
 
-// Polls for ready network connections.
+// netpoll checks for ready network connections.
 // Returns list of goroutines that become runnable.
-func netpoll(block bool) gList {
+// delay < 0: blocks indefinitely
+// delay == 0: does not block, just polls
+// delay > 0: block for up to that many nanoseconds
+func netpoll(delay int64) gList {
 	if kq == -1 {
 		return gList{}
 	}
 	var tp *timespec
 	var ts timespec
-	if !block {
+	if delay < 0 {
+		tp = nil
+	} else if delay == 0 {
+		tp = &ts
+	} else {
+		ts.setNsec(delay)
+		if ts.tv_sec > 1e6 {
+			// Darwin returns EINVAL if the sleep time is too long.
+			ts.tv_sec = 1e6
+		}
 		tp = &ts
 	}
 	var events [64]keventt
@@ -76,6 +88,11 @@ retry:
 			println("runtime: kevent on fd", kq, "failed with", -n)
 			throw("runtime: netpoll failed")
 		}
+		// If a timed sleep was interrupted, just return to
+		// recalculate how long we should sleep now.
+		if delay > 0 {
+			return gList{}
+		}
 		goto retry
 	}
 	var toRun gList
@@ -110,8 +127,5 @@ retry:
 			netpollready(&toRun, pd, mode)
 		}
 	}
-	if block && toRun.empty() {
-		goto retry
-	}
 	return toRun
 }

src/runtime/netpoll_solaris.go

@@ -178,27 +178,45 @@ func netpollarm(pd *pollDesc, mode int) {
 	unlock(&pd.lock)
 }
 
-// polls for ready network connections
-// returns list of goroutines that become runnable
-func netpoll(block bool) gList {
+// netpoll checks for ready network connections.
+// Returns list of goroutines that become runnable.
+// delay < 0: blocks indefinitely
+// delay == 0: does not block, just polls
+// delay > 0: block for up to that many nanoseconds
+func netpoll(delay int64) gList {
 	if portfd == -1 {
 		return gList{}
 	}
 
 	var wait *timespec
-	var zero timespec
-	if !block {
-		wait = &zero
+	var ts timespec
+	if delay < 0 {
+		wait = nil
+	} else if delay == 0 {
+		wait = &ts
+	} else {
+		ts.setNsec(delay)
+		if ts.tv_sec > 1e6 {
+			// An arbitrary cap on how long to wait for a timer.
+			// 1e6 s == ~11.5 days.
+			ts.tv_sec = 1e6
+		}
+		wait = &ts
 	}
 
 	var events [128]portevent
 retry:
 	var n uint32 = 1
 	if port_getn(portfd, &events[0], uint32(len(events)), &n, wait) < 0 {
-		if e := errno(); e != _EINTR {
+		if e := errno(); e != _EINTR && e != _ETIME {
 			print("runtime: port_getn on fd ", portfd, " failed (errno=", e, ")\n")
 			throw("runtime: netpoll failed")
 		}
+		// If a timed sleep was interrupted, just return to
+		// recalculate how long we should sleep now.
+		if delay > 0 {
+			return gList{}
+		}
 		goto retry
 	}
 
@@ -242,8 +260,5 @@ retry:
 		}
 	}
 
-	if block && toRun.empty() {
-		goto retry
-	}
 	return toRun
 }

src/runtime/netpoll_stub.go

@@ -10,7 +10,7 @@ var netpollWaiters uint32
 
 // Polls for ready network connections.
 // Returns list of goroutines that become runnable.
-func netpoll(block bool) gList {
+func netpoll(delay int64) gList {
 	// Implementation for platforms that do not support
 	// integrated network poller.
 	return gList{}

src/runtime/netpoll_windows.go

@@ -61,9 +61,12 @@ func netpollarm(pd *pollDesc, mode int) {
 	throw("runtime: unused")
 }
 
-// Polls for completed network IO.
+// netpoll checks for ready network connections.
 // Returns list of goroutines that become runnable.
-func netpoll(block bool) gList {
+// delay < 0: blocks indefinitely
+// delay == 0: does not block, just polls
+// delay > 0: block for up to that many nanoseconds
+func netpoll(delay int64) gList {
 	var entries [64]overlappedEntry
 	var wait, qty, key, flags, n, i uint32
 	var errno int32
@@ -75,23 +78,32 @@ func netpoll(block bool) gList {
 	if iocphandle == _INVALID_HANDLE_VALUE {
 		return gList{}
 	}
-	wait = 0
-	if block {
+	if delay < 0 {
 		wait = _INFINITE
+	} else if delay == 0 {
+		wait = 0
+	} else if delay < 1e6 {
+		wait = 1
+	} else if delay < 1e15 {
+		wait = uint32(delay / 1e6)
+	} else {
+		// An arbitrary cap on how long to wait for a timer.
+		// 1e9 ms == ~11.5 days.
+		wait = 1e9
 	}
-retry:
+
 	if _GetQueuedCompletionStatusEx != nil {
 		n = uint32(len(entries) / int(gomaxprocs))
 		if n < 8 {
 			n = 8
 		}
-		if block {
+		if delay != 0 {
 			mp.blocked = true
 		}
 		if stdcall6(_GetQueuedCompletionStatusEx, iocphandle, uintptr(unsafe.Pointer(&entries[0])), uintptr(n), uintptr(unsafe.Pointer(&n)), uintptr(wait), 0) == 0 {
 			mp.blocked = false
 			errno = int32(getlasterror())
-			if !block && errno == _WAIT_TIMEOUT {
+			if errno == _WAIT_TIMEOUT {
 				return gList{}
 			}
 			println("runtime: GetQueuedCompletionStatusEx failed (errno=", errno, ")")
@@ -111,13 +123,13 @@ retry:
 		op = nil
 		errno = 0
 		qty = 0
-		if block {
+		if delay != 0 {
 			mp.blocked = true
 		}
 		if stdcall5(_GetQueuedCompletionStatus, iocphandle, uintptr(unsafe.Pointer(&qty)), uintptr(unsafe.Pointer(&key)), uintptr(unsafe.Pointer(&op)), uintptr(wait)) == 0 {
 			mp.blocked = false
 			errno = int32(getlasterror())
-			if !block && errno == _WAIT_TIMEOUT {
+			if errno == _WAIT_TIMEOUT {
 				return gList{}
 			}
 			if op == nil {
@@ -129,9 +141,6 @@ retry:
 		mp.blocked = false
 		handlecompletion(&toRun, op, errno, qty)
 	}
-	if block && toRun.empty() {
-		goto retry
-	}
 	return toRun
 }
 

src/runtime/proc.go

@@ -1116,7 +1116,7 @@ func stopTheWorldWithSema() {
 func startTheWorldWithSema(emitTraceEvent bool) int64 {
 	mp := acquirem() // disable preemption because it can be holding p in a local var
 	if netpollinited() {
-		list := netpoll(false) // non-blocking
+		list := netpoll(0) // non-blocking
 		injectglist(&list)
 	}
 	lock(&sched.lock)
@@ -2252,7 +2252,7 @@ top:
 	// not set lastpoll yet), this thread will do blocking netpoll below
 	// anyway.
 	if netpollinited() && atomic.Load(&netpollWaiters) > 0 && atomic.Load64(&sched.lastpoll) != 0 {
-		if list := netpoll(false); !list.empty() { // non-blocking
+		if list := netpoll(0); !list.empty() { // non-blocking
 			gp := list.pop()
 			injectglist(&list)
 			casgstatus(gp, _Gwaiting, _Grunnable)
@@ -2406,14 +2406,16 @@ stop:
 		if _g_.m.spinning {
 			throw("findrunnable: netpoll with spinning")
 		}
-		list := netpoll(true) // block until new work is available
+		list := netpoll(-1) // block until new work is available
 		atomic.Store64(&sched.lastpoll, uint64(nanotime()))
-		if !list.empty() {
 		lock(&sched.lock)
 		_p_ = pidleget()
 		unlock(&sched.lock)
-			if _p_ != nil {
+		if _p_ == nil {
+			injectglist(&list)
+		} else {
 			acquirep(_p_)
+			if !list.empty() {
 				gp := list.pop()
 				injectglist(&list)
 				casgstatus(gp, _Gwaiting, _Grunnable)
@@ -2422,7 +2424,11 @@ stop:
 				}
 				return gp, false
 			}
-			injectglist(&list)
+			if wasSpinning {
+				_g_.m.spinning = true
+				atomic.Xadd(&sched.nmspinning, 1)
+			}
+			goto top
 		}
 	}
 	stopm()
@@ -2442,7 +2448,7 @@ func pollWork() bool {
 		return true
 	}
 	if netpollinited() && atomic.Load(&netpollWaiters) > 0 && sched.lastpoll != 0 {
-		if list := netpoll(false); !list.empty() {
+		if list := netpoll(0); !list.empty() {
 			injectglist(&list)
 			return true
 		}
@@ -4371,7 +4377,7 @@ func sysmon() {
 		now := nanotime()
 		if netpollinited() && lastpoll != 0 && lastpoll+10*1000*1000 < now {
 			atomic.Cas64(&sched.lastpoll, uint64(lastpoll), uint64(now))
-			list := netpoll(false) // non-blocking - returns list of goroutines
+			list := netpoll(0) // non-blocking - returns list of goroutines
 			if !list.empty() {
 				// Need to decrement number of idle locked M's
 				// (pretending that one more is running) before injectglist.