runtime: dequeue the correct SudoG
select {
case <- c:
case <- c:
}
In this case, c.recvq lists two SudoGs which have the same G.
So we can't use the G as the key to dequeue the correct SudoG,
as that key is ambiguous. Dequeueing the wrong SudoG ends up
freeing a SudoG that is still in c.recvq.
The fix is to use the actual SudoG pointer as the key.
LGTM=dvyukov
R=rsc, bradfitz, dvyukov, khr
CC=austin, golang-codereviews
https://golang.org/cl/159040043
diff --git a/src/runtime/select.go b/src/runtime/select.go
index 9de057b..efe68c1 100644
--- a/src/runtime/select.go
+++ b/src/runtime/select.go
@@ -398,9 +398,9 @@
} else {
c = k._chan
if k.kind == _CaseSend {
- c.sendq.dequeueg(gp)
+ c.sendq.dequeueSudoG(sglist)
} else {
- c.recvq.dequeueg(gp)
+ c.recvq.dequeueSudoG(sglist)
}
}
sgnext = sglist.waitlink
@@ -628,7 +628,7 @@
return
}
-func (q *waitq) dequeueg(gp *g) {
+func (q *waitq) dequeueSudoG(s *sudog) {
var prevsgp *sudog
l := &q.first
for {
@@ -636,7 +636,7 @@
if sgp == nil {
return
}
- if sgp.g == gp {
+ if sgp == s {
*l = sgp.next
if q.last == sgp {
q.last = prevsgp
