runtime: fix deadlock when gctrace
Calling ReadMemStats which does stoptheworld on m0 holding locks
was not a good idea.
Stoptheworld holding locks is a recipe for deadlocks (added check for this).
Stoptheworld on g0 may or may not work (added check for this as well).
As far as I understand scavenger will print incorrect numbers now,
as stack usage is not subtracted from heap. But it's better than deadlocking.
LGTM=khr
R=golang-codereviews, rsc, khr
CC=golang-codereviews, rlh
https://golang.org/cl/124670043
diff --git a/src/pkg/runtime/malloc.go b/src/pkg/runtime/malloc.go
index 8ee4607..578fbd1 100644
--- a/src/pkg/runtime/malloc.go
+++ b/src/pkg/runtime/malloc.go
@@ -413,6 +413,7 @@
return
}
releasem(mp)
+ mp = nil
if panicking != 0 {
return
@@ -441,7 +442,11 @@
startTime := gonanotime()
mp = acquirem()
mp.gcing = 1
+ releasem(mp)
stoptheworld()
+ if mp != acquirem() {
+ gothrow("gogc: rescheduled")
+ }
clearpools()
@@ -474,6 +479,7 @@
semrelease(&worldsema)
starttheworld()
releasem(mp)
+ mp = nil
// now that gc is done, kick off finalizer thread if needed
if !concurrentSweep {
