runtime: clear sg.selectdone before saving in SudoG cache
Removes another dangling pointer that might
cause a memory leak in 1.4 or crash the GC in 1.5.
LGTM=rlh
R=golang-codereviews
CC=golang-codereviews, iant, khr, r, rlh
https://golang.org/cl/150520043
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 76e3ff8..5b8c7d8 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -174,6 +174,9 @@
if s.elem != nil {
gothrow("runtime: sudog with non-nil elem")
}
+ if s.selectdone != nil {
+ gothrow("runtime: sudog with non-nil selectdone")
+ }
gp := getg()
if gp.param != nil {
gothrow("runtime: releaseSudog with non-nil gp.param")
diff --git a/src/runtime/select.go b/src/runtime/select.go
index 1bcea8c..9de057b 100644
--- a/src/runtime/select.go
+++ b/src/runtime/select.go
@@ -377,8 +377,14 @@
// iterating through the linked list they are in reverse order.
cas = nil
sglist = gp.waiting
- // Clear all elem before unlinking from gp.waiting.
+ // Clear all selectdone and elem before unlinking from gp.waiting.
+ // They must be cleared before being put back into the sudog cache.
+ // Clear before unlinking, because if a stack copy happens after the unlink,
+ // they will not be updated, they will be left pointing to the old stack,
+ // which creates dangling pointers, which may be detected by the
+ // garbage collector.
for sg1 := gp.waiting; sg1 != nil; sg1 = sg1.waitlink {
+ sg1.selectdone = nil
sg1.elem = nil
}
gp.waiting = nil
