runtime: introduce gcMode type for GC modes

Currently, the GC modes constants are untyped and functions pass them
around as ints. Clean this up by introducing a proper type for these
constant.

Change-Id: Ibc022447bdfa203644921fbb548312d7e2272e8d
Reviewed-on: https://go-review.googlesource.com/14981
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 848e8f69927b48fc58e945e46f1e424108029e8d..a3960852a1e7d8dd137cdf43cc9cc37d4c776c37 100644 (file)
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -803,10 +803,13 @@ func GC() {
        startGC(gcForceBlockMode, false)
 }
 
+// gcMode indicates how concurrent a GC cycle should be.
+type gcMode int
+
 const (
-       gcBackgroundMode = iota // concurrent GC
-       gcForceMode             // stop-the-world GC now
-       gcForceBlockMode        // stop-the-world GC now and wait for sweep
+       gcBackgroundMode gcMode = iota // concurrent GC and sweep
+       gcForceMode                    // stop-the-world GC now, concurrent sweep
+       gcForceBlockMode               // stop-the-world GC now and STW sweep
 )
 
 // startGC starts a GC cycle. If mode is gcBackgroundMode, this will
@@ -814,7 +817,7 @@ const (
 // until the new GC cycle is started and finishes. If forceTrigger is
 // true, it indicates that GC should be started regardless of the
 // current heap size.
-func startGC(mode int, forceTrigger bool) {
+func startGC(mode gcMode, forceTrigger bool) {
        // The gc is turned off (via enablegc) until the bootstrap has completed.
        // Also, malloc gets called in the guts of a number of libraries that might be
        // holding locks. To avoid deadlocks during stop-the-world, don't bother
@@ -889,7 +892,7 @@ func backgroundgc() {
        }
 }
 
-func gc(mode int) {
+func gc(mode gcMode) {
        // Timing/utilization tracking
        var stwprocs, maxprocs int32
        var tSweepTerm, tScan, tInstallWB, tMark, tMarkTerm int64
@@ -1513,7 +1516,7 @@ func gcMark(start_time int64) {
        }
 }
 
-func gcSweep(mode int) {
+func gcSweep(mode gcMode) {
        if gcphase != _GCoff {
                throw("gcSweep being done but phase is not GCoff")
        }