runtime: improve comment in concurrent GC

"Sync" is not very informative. What's being synchronized and with
whom? Update this comment to explain what we're really doing: enabling
write barriers.

Change-Id: I4f0cbb8771988c7ba4606d566b77c26c64165f0f
Reviewed-on: https://go-review.googlesource.com/7700
Reviewed-by: Rick Hudson <rlh@golang.org>

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 0b15a8500d2d30c3062525af25d4caa00aca9409..d19606bba78c35134584ffe4b31bf30d0cf7c47b 100644 (file)
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -333,7 +333,7 @@ func gc(mode int) {
                        gcscan_m()
                        gctimer.cycle.installmarkwb = nanotime()
 
-                       // Sync.
+                       // Enter mark phase and enable write barriers.
                        stoptheworld()
                        gcphase = _GCmark