[dev.regabi] all: merge master (c9fb4eb) into dev.regabi

Merge List:

* 2020-12-22 c9fb4eb0a2 cmd/link: handle grouped resource sections
* 2020-12-22 c06a354bcc test: trigger SIGSEGV instead of SIGTRAP in issue11656.go
* 2020-12-22 0aa9b4709a cmd/pack: r command create output file if not exist
* 2020-12-22 4d27c4c223 runtime: correct error handling in several FreeBSD syscall wrappers
* 2020-12-22 9b6147120a cmd/pack: treat compiler's -linkobj output as "compiler object"
* 2020-12-21 bc7e4d9257 syscall: don't generate ptrace on iOS
* 2020-12-21 6cff874c47 runtime/metrics: add Read examples
* 2020-12-21 8438a5779b runtime: use _exit on darwin
* 2020-12-21 cb95819cf6 runtime: detect netbsd netpoll overrun in sysmon
* 2020-12-21 53c984d976 runtime: skip wakep call in wakeNetPoller on Plan 9
* 2020-12-21 9abbe27710 test: skip issue11656.go on mips/mips64/ppc64

Change-Id: Ibb235fbf6a86ebcf50c686dc11f7c02d1865f845

1 files changed, 23 insertions, 1 deletions

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 64e102fb0a..5adcbf07dc 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -2882,7 +2882,9 @@ func wakeNetPoller(when int64) {
 	} else {
 		// There are no threads in the network poller, try to get
 		// one there so it can handle new timers.
-		wakep()
+		if GOOS != "plan9" { // Temporary workaround - see issue #42303.
+			wakep()
+		}
 	}
 }
 
@@ -5128,6 +5130,26 @@ func sysmon() {
 			}
 		}
 		mDoFixup()
+		if GOOS == "netbsd" {
+			// netpoll is responsible for waiting for timer
+			// expiration, so we typically don't have to worry
+			// about starting an M to service timers. (Note that
+			// sleep for timeSleepUntil above simply ensures sysmon
+			// starts running again when that timer expiration may
+			// cause Go code to run again).
+			//
+			// However, netbsd has a kernel bug that sometimes
+			// misses netpollBreak wake-ups, which can lead to
+			// unbounded delays servicing timers. If we detect this
+			// overrun, then startm to get something to handle the
+			// timer.
+			//
+			// See issue 42515 and
+			// https://gnats.netbsd.org/cgi-bin/query-pr-single.pl?number=50094.
+			if next, _ := timeSleepUntil(); next < now {
+				startm(nil, false)
+			}
+		}
 		if atomic.Load(&scavenge.sysmonWake) != 0 {
 			// Kick the scavenger awake if someone requested it.
 			wakeScavenger()