From 083938df14c0602a44d055bd3f4427980cf51c27 Mon Sep 17 00:00:00 2001
From: Austin Clements <austin@google.com>
Date: Fri, 10 Aug 2018 10:33:05 -0400
Subject: [PATCH] runtime: use gList for injectglist

Change-Id: Id5af75eaaf41f43bc6baa6d3fe2b852a2f93bb6f
Reviewed-on: https://go-review.googlesource.com/129400
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
---
 src/runtime/mgc.go     |  3 +--
 src/runtime/mgcmark.go |  3 ++-
 src/runtime/proc.go    | 31 ++++++++++++++++---------------
 3 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 2d67c4d8c4..e4c0f5a587 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1630,8 +1630,7 @@ func gcMarkTermination(nextTriggerRatio float64) {
 	// Bump GC cycle count and wake goroutines waiting on sweep.
 	lock(&work.sweepWaiters.lock)
 	memstats.numgc++
-	injectglist(work.sweepWaiters.list.head.ptr())
-	work.sweepWaiters.list = gList{}
+	injectglist(&work.sweepWaiters.list)
 	unlock(&work.sweepWaiters.lock)
 
 	// Finish the current heap profiling cycle and start a new
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index d6ee7ff6fa..69ff895512 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -603,7 +603,8 @@ func gcAssistAlloc1(gp *g, scanWork int64) {
 // new assists from going to sleep after this point.
 func gcWakeAllAssists() {
 	lock(&work.assistQueue.lock)
-	injectglist(work.assistQueue.q.popList().head.ptr())
+	list := work.assistQueue.q.popList()
+	injectglist(&list)
 	unlock(&work.assistQueue.lock)
 }
 
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 5cb7f13016..7875b38e2e 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -1149,7 +1149,7 @@ func startTheWorldWithSema(emitTraceEvent bool) int64 {
 	_g_.m.locks++ // disable preemption because it can be holding p in a local var
 	if netpollinited() {
 		list := netpoll(false) // non-blocking
-		injectglist(list.head.ptr())
+		injectglist(&list)
 	}
 	add := needaddgcproc()
 	lock(&sched.lock)
@@ -2314,7 +2314,7 @@ top:
 	if netpollinited() && atomic.Load(&netpollWaiters) > 0 && atomic.Load64(&sched.lastpoll) != 0 {
 		if list := netpoll(false); !list.empty() { // non-blocking
 			gp := list.pop()
-			injectglist(list.head.ptr())
+			injectglist(&list)
 			casgstatus(gp, _Gwaiting, _Grunnable)
 			if trace.enabled {
 				traceGoUnpark(gp, 0)
@@ -2475,14 +2475,14 @@ stop:
 			if _p_ != nil {
 				acquirep(_p_)
 				gp := list.pop()
-				injectglist(list.head.ptr())
+				injectglist(&list)
 				casgstatus(gp, _Gwaiting, _Grunnable)
 				if trace.enabled {
 					traceGoUnpark(gp, 0)
 				}
 				return gp, false
 			}
-			injectglist(list.head.ptr())
+			injectglist(&list)
 		}
 	}
 	stopm()
@@ -2503,7 +2503,7 @@ func pollWork() bool {
 	}
 	if netpollinited() && atomic.Load(&netpollWaiters) > 0 && sched.lastpoll != 0 {
 		if list := netpoll(false); !list.empty() {
-			injectglist(list.head.ptr())
+			injectglist(&list)
 			return true
 		}
 	}
@@ -2528,22 +2528,21 @@ func resetspinning() {
 	}
 }
 
-// Injects the list of runnable G's into the scheduler.
+// Injects the list of runnable G's into the scheduler and clears glist.
 // Can run concurrently with GC.
-func injectglist(glist *g) {
-	if glist == nil {
+func injectglist(glist *gList) {
+	if glist.empty() {
 		return
 	}
 	if trace.enabled {
-		for gp := glist; gp != nil; gp = gp.schedlink.ptr() {
+		for gp := glist.head.ptr(); gp != nil; gp = gp.schedlink.ptr() {
 			traceGoUnpark(gp, 0)
 		}
 	}
 	lock(&sched.lock)
 	var n int
-	for n = 0; glist != nil; n++ {
-		gp := glist
-		glist = gp.schedlink.ptr()
+	for n = 0; !glist.empty(); n++ {
+		gp := glist.pop()
 		casgstatus(gp, _Gwaiting, _Grunnable)
 		globrunqput(gp)
 	}
@@ -2551,6 +2550,7 @@ func injectglist(glist *g) {
 	for ; n != 0 && sched.npidle != 0; n-- {
 		startm(nil, false)
 	}
+	*glist = gList{}
 }
 
 // One round of scheduler: find a runnable goroutine and execute it.
@@ -4389,7 +4389,7 @@ func sysmon() {
 				// observes that there is no work to do and no other running M's
 				// and reports deadlock.
 				incidlelocked(-1)
-				injectglist(list.head.ptr())
+				injectglist(&list)
 				incidlelocked(1)
 			}
 		}
@@ -4404,8 +4404,9 @@ func sysmon() {
 		if t := (gcTrigger{kind: gcTriggerTime, now: now}); t.test() && atomic.Load(&forcegc.idle) != 0 {
 			lock(&forcegc.lock)
 			forcegc.idle = 0
-			forcegc.g.schedlink = 0
-			injectglist(forcegc.g)
+			var list gList
+			list.push(forcegc.g)
+			injectglist(&list)
 			unlock(&forcegc.lock)
 		}
 		// scavenge heap once in a while
-- 
2.50.0