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>

1 files changed, 25 insertions, 10 deletions

diff --git a/src/runtime/netpoll_solaris.go b/src/runtime/netpoll_solaris.go
index ddddb27962..ad41ab5af2 100644
--- a/src/runtime/netpoll_solaris.go
+++ b/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
 }