Merge "build: limit concurrency of updateSymlinks" into main (5a5b7a80) · Commits · e / os / android_build_soong

ui/build/soong.go

+18 −3

Original line number	Diff line number	Diff line
		@@ -433,13 +433,13 @@ func checkEnvironmentFile(ctx Context, currentEnv *Environment, envFile string)
		}
		}

		func updateSymlinks(ctx Context, dir, prevCWD, cwd string) error {
		func updateSymlinks(ctx Context, dir, prevCWD, cwd string, updateSemaphore chan struct{}) error {
		defer symlinkWg.Done()

		visit := func(path string, d fs.DirEntry, err error) error {
		if d.IsDir() && path != dir {
		symlinkWg.Add(1)
		go updateSymlinks(ctx, path, prevCWD, cwd)
		go updateSymlinks(ctx, path, prevCWD, cwd, updateSemaphore)
		return filepath.SkipDir
		}
		f, err := d.Info()
		@@ -470,12 +470,27 @@ func updateSymlinks(ctx Context, dir, prevCWD, cwd string) error {
		return nil
		}

		<-updateSemaphore
		defer func() { updateSemaphore <- struct{}{} }()
		if err := filepath.WalkDir(dir, visit); err != nil {
		return err
		}
		return nil
		}

		// b/376466642: If the concurrency of updateSymlinks is unbounded, Go's runtime spawns a
		// theoretically unbounded number of threads to handle blocking syscalls. This causes the runtime to
		// panic due to hitting thread limits in rare cases. Limiting to GOMAXPROCS concurrent symlink
		// updates should make this a non-issue.
		func newUpdateSemaphore() chan struct{} {
		numPermits := runtime.GOMAXPROCS(0)
		c := make(chan struct{}, numPermits)
		for i := 0; i < numPermits; i++ {
		c <- struct{}{}
		}
		return c
		}

		func fixOutDirSymlinks(ctx Context, config Config, outDir string) error {
		cwd, err := os.Getwd()
		if err != nil {
		@@ -508,7 +523,7 @@ func fixOutDirSymlinks(ctx Context, config Config, outDir string) error {
		}

		symlinkWg.Add(1)
		if err := updateSymlinks(ctx, outDir, prevCWD, cwd); err != nil {
		if err := updateSymlinks(ctx, outDir, prevCWD, cwd, newUpdateSemaphore()); err != nil {
		return err
		}
		symlinkWg.Wait()