fix panic in bitswap working limit spawning

License: MIT
Signed-off-by: Jeromy <jeromyj@gmail.com>

workers.go

@@ -5,7 +5,6 @@ import (
 
 	process "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess"
 	procctx "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess/context"
-	ratelimit "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess/ratelimit"
 	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
 
 	key "github.com/ipfs/go-ipfs/blocks/key"
@@ -74,11 +73,14 @@ func (bs *Bitswap) taskWorker(ctx context.Context, id int) {
 
 func (bs *Bitswap) provideWorker(px process.Process) {
 
-	limiter := ratelimit.NewRateLimiter(px, provideWorkerMax)
+	limit := make(chan struct{}, provideWorkerMax)
 
 	limitedGoProvide := func(k key.Key, wid int) {
+		defer func() {
+			// replace token when done
+			<-limit
+		}()
 		ev := logging.LoggableMap{"ID": wid}
-		limiter.LimitedGo(func(px process.Process) {
 
 		ctx := procctx.OnClosingContext(px) // derive ctx from px
 		defer log.EventBegin(ctx, "Bitswap.ProvideWorker.Work", ev, &k).Done()
@@ -89,12 +91,10 @@ func (bs *Bitswap) provideWorker(px process.Process) {
 		if err := bs.network.Provide(ctx, k); err != nil {
 			log.Error(err)
 		}
-		})
 	}
 
 	// worker spawner, reads from bs.provideKeys until it closes, spawning a
 	// _ratelimited_ number of workers to handle each key.
-	limiter.Go(func(px process.Process) {
 	for wid := 2; ; wid++ {
 		ev := logging.LoggableMap{"ID": 1}
 		log.Event(procctx.OnClosingContext(px), "Bitswap.ProvideWorker.Loop", ev)
@@ -107,10 +107,14 @@ func (bs *Bitswap) provideWorker(px process.Process) {
 				log.Debug("provideKeys channel closed")
 				return
 			}
-				limitedGoProvide(k, wid)
+			select {
+			case <-px.Closing():
+				return
+			case limit <- struct{}{}:
+				go limitedGoProvide(k, wid)
+			}
 		}
 	}
-	})
 }
 
 func (bs *Bitswap) provideCollector(ctx context.Context) {