Merge pull request #14354 from vrothberg/fix-14351

work queue: simplify and use a wait group

libpod/runtime.go

@@ -11,6 +11,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 
@@ -87,8 +88,8 @@ type Runtime struct {
 	lockManager            lock.Manager
 
 	// Worker
-	workerShutdown chan bool
-	workerChannel  chan func()
+	workerChannel chan func()
+	workerGroup   sync.WaitGroup
 
 	// syslog describes whenever logrus should log to the syslog as well.
 	// Note that the syslog hook will be enabled early in cmd/podman/syslog_linux.go
@@ -823,12 +824,9 @@ func (r *Runtime) Shutdown(force bool) error {
 		return define.ErrRuntimeStopped
 	}
 
-	if r.workerShutdown != nil {
-		// Signal the worker routine to shutdown.  The routine will
-		// process all pending work items and then read from the
-		// channel; we're blocked until all work items have been
-		// processed.
-		r.workerShutdown <- true
+	if r.workerChannel != nil {
+		r.workerGroup.Wait()
+		close(r.workerChannel)
 	}
 
 	r.valid = false

libpod/runtime_worker.go

@@ -1,40 +1,17 @@
 package libpod
 
-import (
-	"time"
-)
-
 func (r *Runtime) startWorker() {
-	if r.workerChannel == nil {
-		r.workerChannel = make(chan func(), 1)
-		r.workerShutdown = make(chan bool)
-	}
+	r.workerChannel = make(chan func(), 10)
 	go func() {
-		for {
-			// Make sure to read all workers before
-			// checking if we're about to shutdown.
-			for len(r.workerChannel) > 0 {
-				w := <-r.workerChannel
-				w()
-			}
-
-			select {
-			// We'll read from the shutdown channel only when all
-			// items above have been processed.
-			//
-			// (*Runtime).Shutdown() will block until until the
-			// item is read.
-			case <-r.workerShutdown:
-				return
-
-			default:
-				time.Sleep(100 * time.Millisecond)
-			}
+		for w := range r.workerChannel {
+			w()
+			r.workerGroup.Done()
 		}
 	}()
 }
 
 func (r *Runtime) queueWork(f func()) {
+	r.workerGroup.Add(1)
 	go func() {
 		r.workerChannel <- f
 	}()