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Commit 5c12c667 authored by Bob Badour's avatar Bob Badour
Browse files

Replace nil-able *sync.Waitgroup with sync.Once 

Simplifies synchronization and eliminates lock for nil waitroup.

Test: m droid

Test: m out/soong/.intermediates/packages/modules/StatsD/apex/com.android.os.statsd/android_common_com.android.os.statsd_image/NOTICE.html.gz

Change-Id: I381ee79e142214e7331241071f076db2f7960ba6
parent d2c28ba8

tools/compliance/graph.go

+4 −6
Original line number Diff line number Diff line
@@ -58,13 +58,11 @@ type LicenseGraph struct { 
	/// (guarded by mu)

	targets map[string]*TargetNode



	// wgBU becomes non-nil when the bottom-up resolve begins and reaches 0

	// (i.e. Wait() proceeds) when the bottom-up resolve completes. (guarded by mu)

	wgBU *sync.WaitGroup

	// onceBottomUp makes sure the bottom-up resolve walk only happens one time.

	onceBottomUp sync.Once



	// wgTD becomes non-nil when the top-down resolve begins and reaches 0 (i.e. Wait()

	// proceeds) when the top-down resolve completes. (guarded by mu)

	wgTD *sync.WaitGroup

	// onceTopDown makes sure the top-down resolve walk only happens one time.

	onceTopDown sync.Once



	// shippedNodes caches the results of a full walk of nodes identifying targets

	// distributed either directly or as derivative works. (creation guarded by mu)

tools/compliance/policy_resolve.go

+112 −132
Original line number Diff line number Diff line
@@ -49,19 +49,7 @@ func ResolveBottomUpConditions(lg *LicenseGraph) { 
func TraceBottomUpConditions(lg *LicenseGraph, conditionsFn TraceConditions) {



	// short-cut if already walked and cached

	lg.mu.Lock()

	wg := lg.wgBU



	if wg != nil {

		lg.mu.Unlock()

		wg.Wait()

		return

	}

	wg = &sync.WaitGroup{}

	wg.Add(1)

	lg.wgBU = wg

	lg.mu.Unlock()



	lg.onceBottomUp.Do(func() {

		// amap identifes targets previously walked. (guarded by mu)

		amap := make(map[*TargetNode]struct{})
@@ -125,8 +113,7 @@ func TraceBottomUpConditions(lg *LicenseGraph, conditionsFn TraceConditions) { 
			rnode := lg.targets[rname]

			_ = walk(rnode, rnode.IsContainer())

		}



	wg.Done()

	})

}



// ResolveTopDownCondtions performs a top-down walk of the LicenseGraph
@@ -145,18 +132,9 @@ func ResolveTopDownConditions(lg *LicenseGraph) { 
func TraceTopDownConditions(lg *LicenseGraph, conditionsFn TraceConditions) {



	// short-cut if already walked and cached

	lg.mu.Lock()

	wg := lg.wgTD



	if wg != nil {

		lg.mu.Unlock()

		wg.Wait()

		return

	}

	wg = &sync.WaitGroup{}

	lg.onceTopDown.Do(func() {

		wg := &sync.WaitGroup{}

		wg.Add(1)

	lg.wgTD = wg

	lg.mu.Unlock()



		// start with the conditions propagated up the graph

		TraceBottomUpConditions(lg, conditionsFn)
@@ -174,6 +152,7 @@ func TraceTopDownConditions(lg *LicenseGraph, conditionsFn TraceConditions) { 
			continueWalk := func() bool {

				mu.Lock()

				defer mu.Unlock()



				depcs := fnode.resolution

				_, alreadyWalked := amap[fnode]

				if alreadyWalked {
@@ -224,4 +203,5 @@ func TraceTopDownConditions(lg *LicenseGraph, conditionsFn TraceConditions) { 
		}

		wg.Done()

		wg.Wait()

	})

}