runtime: note a minor issue with GODEUG=gcstoptheworld

Change-Id: I91cda8d88b0852cd0f868d33c594206bcca0c386
Reviewed-on: https://go-review.googlesource.com/16352
Reviewed-by: Rick Hudson <rlh@golang.org>

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 88cee5b8f69527c7a25afb3043241f98aae7bbe6..235c1aac5db84dd50ce4c2815b2f9457f5cd2952 100644 (file)
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -916,6 +916,9 @@ func startGC(mode gcMode, forceTrigger bool) {
        releasem(mp)
        mp = nil
 
+       // TODO: In gcstoptheworld debug mode, multiple goroutines may
+       // detect the heap trigger simultaneously and then start
+       // multiple STW GCs, which will run sequentially.
        if debug.gcstoptheworld == 1 {
                mode = gcForceMode
        } else if debug.gcstoptheworld == 2 {