context: Allow running some singletons in parallel.

Many of the singletons are trivial and can be run in parallel, improving
the performance during analysis.

Bug: 281536768
Test: manual, presubmit
Change-Id: Ia63e4bc42a68e65dfa800e770982fa5826355fad

bootstrap/command.go

@@ -91,7 +91,7 @@ func RunBlueprint(args Args, stopBefore StopBefore, ctx *blueprint.Context, conf
 	ctx.RegisterBottomUpMutator("bootstrap_plugin_deps", pluginDeps)
 	ctx.RegisterModuleType("bootstrap_go_package", newGoPackageModuleFactory())
 	ctx.RegisterModuleType("blueprint_go_binary", newGoBinaryModuleFactory())
-	ctx.RegisterSingletonType("bootstrap", newSingletonFactory())
+	ctx.RegisterSingletonType("bootstrap", newSingletonFactory(), false)
 	blueprint.RegisterPackageIncludesModuleType(ctx)
 
 	ctx.BeginEvent("parse_bp")

bootstrap/glob.go

@@ -227,7 +227,7 @@ func generateGlobNinjaFile(glob *GlobSingleton, config interface{}) ([]byte, []e
 	ctx := blueprint.NewContext()
 	ctx.RegisterSingletonType("glob", func() blueprint.Singleton {
 		return glob
-	})
+	}, false)
 
 	extraDeps, errs := ctx.ResolveDependencies(config)
 	if len(extraDeps) > 0 {

context.go

@@ -441,6 +441,7 @@ type singletonInfo struct {
 	factory   SingletonFactory
 	singleton Singleton
 	name      string
+	parallel  bool
 
 	// set during PrepareBuildActions
 	actionDefs localBuildActions
@@ -566,13 +567,15 @@ type SingletonFactory func() Singleton
 
 // RegisterSingletonType registers a singleton type that will be invoked to
 // generate build actions.  Each registered singleton type is instantiated
-// and invoked exactly once as part of the generate phase.  Each registered
-// singleton is invoked in registration order.
+// and invoked exactly once as part of the generate phase.
+//
+// Those singletons registered with parallel=true are run in parallel, after
+// which the other registered singletons are run in registration order.
 //
 // The singleton type names given here must be unique for the context.  The
 // factory function should be a named function so that its package and name can
 // be included in the generated Ninja file for debugging purposes.
-func (c *Context) RegisterSingletonType(name string, factory SingletonFactory) {
+func (c *Context) RegisterSingletonType(name string, factory SingletonFactory, parallel bool) {
 	for _, s := range c.singletonInfo {
 		if s.name == name {
 			panic(fmt.Errorf("singleton %q is already registered", name))
@@ -583,6 +586,7 @@ func (c *Context) RegisterSingletonType(name string, factory SingletonFactory) {
 		factory:   factory,
 		singleton: factory(),
 		name:      name,
+		parallel:  parallel,
 	})
 }
 
@@ -605,6 +609,7 @@ func (c *Context) RegisterPreSingletonType(name string, factory SingletonFactory
 		factory:   factory,
 		singleton: factory(),
 		name:      name,
+		parallel:  false,
 	})
 }
 
@@ -3314,6 +3319,8 @@ func spliceModules(modules modulesOrAliases, i int, newModules modulesOrAliases)
 func (c *Context) generateModuleBuildActions(config interface{},
 	liveGlobals *liveTracker) ([]string, []error) {
 
+	c.BeginEvent("generateModuleBuildActions")
+	defer c.EndEvent("generateModuleBuildActions")
 	var deps []string
 	var errs []error
 
@@ -3411,13 +3418,12 @@ func (c *Context) generateModuleBuildActions(config interface{},
 	return deps, errs
 }
 
-func (c *Context) generateSingletonBuildActions(config interface{},
-	singletons []*singletonInfo, liveGlobals *liveTracker) ([]string, []error) {
+func (c *Context) generateOneSingletonBuildActions(config interface{},
+	info *singletonInfo, liveGlobals *liveTracker) ([]string, []error) {
 
 	var deps []string
 	var errs []error
 
-	for _, info := range singletons {
 	// The parent scope of the singletonContext's local scope gets overridden to be that of the
 	// calling Go package on a per-call basis.  Since the initial parent scope doesn't matter we
 	// just set it to nil.
@@ -3448,10 +3454,7 @@ func (c *Context) generateSingletonBuildActions(config interface{},
 
 	if len(sctx.errs) > 0 {
 		errs = append(errs, sctx.errs...)
-			if len(errs) > maxErrors {
-				break
-			}
-			continue
+		return deps, errs
 	}
 
 	deps = append(deps, sctx.ninjaFileDeps...)
@@ -3459,10 +3462,89 @@ func (c *Context) generateSingletonBuildActions(config interface{},
 	newErrs := c.processLocalBuildActions(&info.actionDefs,
 		&sctx.actionDefs, liveGlobals)
 	errs = append(errs, newErrs...)
+	return deps, errs
+}
+
+func (c *Context) generateParallelSingletonBuildActions(config interface{},
+	singletons []*singletonInfo, liveGlobals *liveTracker) ([]string, []error) {
+
+	c.BeginEvent("generateParallelSingletonBuildActions")
+	defer c.EndEvent("generateParallelSingletonBuildActions")
+
+	var deps []string
+	var errs []error
+
+	wg := sync.WaitGroup{}
+	cancelCh := make(chan struct{})
+	depsCh := make(chan []string)
+	errsCh := make(chan []error)
+
+	go func() {
+		for {
+			select {
+			case <-cancelCh:
+				close(cancelCh)
+				return
+			case dep := <-depsCh:
+				deps = append(deps, dep...)
+			case newErrs := <-errsCh:
+				if len(errs) <= maxErrors {
+					errs = append(errs, newErrs...)
+				}
+			}
+		}
+	}()
+
+	for _, info := range singletons {
+		if !info.parallel {
+			// Skip any singletons registered with parallel=false.
+			continue
+		}
+		wg.Add(1)
+		go func(inf *singletonInfo) {
+			defer wg.Done()
+			newDeps, newErrs := c.generateOneSingletonBuildActions(config, inf, liveGlobals)
+			depsCh <- newDeps
+			errsCh <- newErrs
+		}(info)
+	}
+	wg.Wait()
+
+	cancelCh <- struct{}{}
+	<-cancelCh
+
+	return deps, errs
+}
+
+func (c *Context) generateSingletonBuildActions(config interface{},
+	singletons []*singletonInfo, liveGlobals *liveTracker) ([]string, []error) {
+
+	c.BeginEvent("generateSingletonBuildActions")
+	defer c.EndEvent("generateSingletonBuildActions")
+
+	var deps []string
+	var errs []error
+
+	// Run one singleton.  Use a variable to simplify manual validation testing.
+	var runSingleton = func(info *singletonInfo) {
+		c.BeginEvent("singleton:" + info.name)
+		defer c.EndEvent("singleton:" + info.name)
+		newDeps, newErrs := c.generateOneSingletonBuildActions(config, info, liveGlobals)
+		deps = append(deps, newDeps...)
+		errs = append(errs, newErrs...)
+	}
+
+	// First, take care of any singletons that want to run in parallel.
+	deps, errs = c.generateParallelSingletonBuildActions(config, singletons, liveGlobals)
+
+	for _, info := range singletons {
+		if !info.parallel {
+			runSingleton(info)
 			if len(errs) > maxErrors {
 				break
 			}
 		}
+	}
 
 	return deps, errs
 }

module_ctx_test.go

@@ -590,7 +590,7 @@ func TestAddNinjaFileDeps(t *testing.T) {
 	ctx.RegisterBottomUpMutator("testBottomUpMutator", addNinjaDepsTestBottomUpMutator)
 	ctx.RegisterTopDownMutator("testTopDownMutator", addNinjaDepsTestTopDownMutator)
 	ctx.RegisterPreSingletonType("testPreSingleton", addNinjaDepsTestPreSingletonFactory)
-	ctx.RegisterSingletonType("testSingleton", addNinjaDepsTestSingletonFactory)
+	ctx.RegisterSingletonType("testSingleton", addNinjaDepsTestSingletonFactory, false)
 	parseDeps, errs := ctx.ParseBlueprintsFiles("Android.bp", nil)
 	if len(errs) > 0 {
 		t.Errorf("unexpected parse errors:")