examples/audio: a race is detected when seeking

[mat007]

Ebitengine Version

v2.8.5

Operating System

• Windows
• macOS
• Linux
• FreeBSD
• OpenBSD
• Android
• iOS
• Nintendo Switch
• PlayStation 5
• Xbox
• Web Browsers

Go Version (go version)

1.22

What steps will reproduce the problem?

go run -race ./examples/audio

then click on the seek bar while the music is playing

What is the expected result?

The cursor jumps to the clicked location (or at least jumps forward), and the music jumps as well, and keeps playing.

What happens instead?

The cursor does not move, and the music gets all choppy.
Also the console shows a data race. 😅

==================
WARNING: DATA RACE
Write at 0x00c0006cc000 by goroutine 39:
  github.com/hajimehoshi/ebiten/v2/audio/vorbis.(*float32BytesReadSeeker).Read()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/vorbis/float32.go:53 +0x404
  github.com/hajimehoshi/ebiten/v2/audio/vorbis.(*Stream).Read()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/vorbis/vorbis.go:42 +0x5b
  github.com/hajimehoshi/ebiten/v2/audio.(*timeStream).Read()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/player.go:422 +0x111
  github.com/ebitengine/oto/v3/internal/mux.(*playerImpl).read()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:268 +0x11c
  github.com/ebitengine/oto/v3/internal/mux.(*playerImpl).playImpl()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:301 +0x27d
  github.com/ebitengine/oto/v3/internal/mux.(*playerImpl).Seek.deferwrap2()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:345 +0x33
  runtime.deferreturn()
      C:/Program Files/Go/src/runtime/panic.go:605 +0x5d
  github.com/ebitengine/oto/v3/internal/mux.(*Player).Seek()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:336 +0x64
  github.com/ebitengine/oto/v3.(*Player).Seek()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/player.go:79 +0x12
  github.com/hajimehoshi/ebiten/v2/audio.(*playerImpl).SetPosition()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/player.go:294 +0x182
  github.com/hajimehoshi/ebiten/v2/audio.(*Player).SetPosition()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/audio.go:478 +0xee
  main.(*Player).seekBarIfNeeded()
      C:/dev/src/github.com/hajimehoshi/ebiten/examples/audio/main.go:331 +0xbc
  main.(*Player).update()
      C:/dev/src/github.com/hajimehoshi/ebiten/examples/audio/main.go:205 +0x1fd
  main.(*Game).Update()
      C:/dev/src/github.com/hajimehoshi/ebiten/examples/audio/main.go:443 +0x40d
  github.com/hajimehoshi/ebiten/v2.(*gameForUI).Update()
      C:/dev/src/github.com/hajimehoshi/ebiten/gameforui.go:105 +0x42
  github.com/hajimehoshi/ebiten/v2/internal/ui.(*context).updateFrameImpl()
      C:/dev/src/github.com/hajimehoshi/ebiten/internal/ui/context.go:154 +0x591
  github.com/hajimehoshi/ebiten/v2/internal/ui.(*context).updateFrame()
      C:/dev/src/github.com/hajimehoshi/ebiten/internal/ui/context.go:73 +0xa4
  github.com/hajimehoshi/ebiten/v2/internal/ui.(*UserInterface).updateGame()
      C:/dev/src/github.com/hajimehoshi/ebiten/internal/ui/ui_glfw.go:1491 +0x390
  github.com/hajimehoshi/ebiten/v2/internal/ui.(*UserInterface).loopGame()
      C:/dev/src/github.com/hajimehoshi/ebiten/internal/ui/ui_glfw.go:1448 +0xf4
  github.com/hajimehoshi/ebiten/v2/internal/ui.(*UserInterface).runMultiThread.func2()
      C:/dev/src/github.com/hajimehoshi/ebiten/internal/ui/run.go:71 +0x284
  golang.org/x/sync/errgroup.(*Group).Go.func1()
      C:/dev/pkg/mod/golang.org/x/sync@v0.10.0/errgroup/errgroup.go:78 +0x91

Previous read at 0x00c0006cc000 by goroutine 31:
  runtime.slicecopy()
      C:/Program Files/Go/src/runtime/slice.go:355 +0x0
  github.com/ebitengine/oto/v3/internal/mux.(*playerImpl).readSourceToBuffer()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:536 +0x3d9
  github.com/ebitengine/oto/v3/internal/mux.(*Mux).loop()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:108 +0x357
  github.com/ebitengine/oto/v3/internal/mux.New.gowrap1()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:69 +0x33

Goroutine 39 (running) created at:
  golang.org/x/sync/errgroup.(*Group).Go()
      C:/dev/pkg/mod/golang.org/x/sync@v0.10.0/errgroup/errgroup.go:75 +0x124
  github.com/hajimehoshi/ebiten/v2/internal/ui.(*UserInterface).runMultiThread()
      C:/dev/src/github.com/hajimehoshi/ebiten/internal/ui/run.go:55 +0x65d
  github.com/hajimehoshi/ebiten/v2/internal/ui.(*UserInterface).Run()
      C:/dev/src/github.com/hajimehoshi/ebiten/internal/ui/run.go:33 +0x97
  github.com/hajimehoshi/ebiten/v2.RunGameWithOptions()
      C:/dev/src/github.com/hajimehoshi/ebiten/run.go:345 +0x204
  github.com/hajimehoshi/ebiten/v2.RunGame()
      C:/dev/src/github.com/hajimehoshi/ebiten/run.go:236 +0xc4
  main.main()
      C:/dev/src/github.com/hajimehoshi/ebiten/examples/audio/main.go:467 +0xc5

Goroutine 31 (running) created at:
  github.com/ebitengine/oto/v3/internal/mux.New()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/internal/mux/mux.go:69 +0x1a4
  github.com/ebitengine/oto/v3.newContext()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/driver_windows.go:45 +0x44
  github.com/ebitengine/oto/v3.NewContext()
      C:/dev/pkg/mod/github.com/ebitengine/oto/v3@v3.4.0-alpha.2/context.go:100 +0x228
  github.com/hajimehoshi/ebiten/v2/audio.newContext()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/context.go:24 +0x97
  github.com/hajimehoshi/ebiten/v2/audio.(*playerFactory).initContextIfNeeded()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/player.go:147 +0xf8
  github.com/hajimehoshi/ebiten/v2/audio.(*playerImpl).ensurePlayer()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/player.go:161 +0x5d
  github.com/hajimehoshi/ebiten/v2/audio.(*playerImpl).Play()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/player.go:193 +0x9d
  github.com/hajimehoshi/ebiten/v2/audio.(*Player).Play()
      C:/dev/src/github.com/hajimehoshi/ebiten/audio/audio.go:455 +0x73b
  main.NewPlayer()
      C:/dev/src/github.com/hajimehoshi/ebiten/examples/audio/main.go:173 +0x704
  main.NewGame()
      C:/dev/src/github.com/hajimehoshi/ebiten/examples/audio/main.go:396 +0x124
  main.main()
      C:/dev/src/github.com/hajimehoshi/ebiten/examples/audio/main.go:463 +0x44
==================

Anything else you feel useful to add?

If we first pause the music by clicking the ⏸️ button, then click the seek bar, then the play button, it works fine.
But I guess being able to do it all at once within the same Update call would be nice. 🤔

[hajimehoshi]

I could reproduce this on macOS too.

[hajimehoshi]

The easiest (but dumb) fix is:

diff --git a/internal/mux/mux.go b/internal/mux/mux.go
index 28df789..67878ae 100644
--- a/internal/mux/mux.go
+++ b/internal/mux/mux.go
@@ -251,10 +251,11 @@ func (p *playerImpl) setBufferSize(bufferSize int) {
 }
 
 func (p *playerImpl) ensureTmpBuf() []byte {
-       if p.tmpbuf == nil {
+       /*if p.tmpbuf == nil {
                p.tmpbuf = make([]byte, p.bufferSize)
        }
-       return p.tmpbuf
+       return p.tmpbuf*/
+       return make([]byte, p.bufferSize)
 }

in Oto.

[hajimehoshi]

The culprit is temporary unlocking locks when reading data

https://github.com/ebitengine/oto/blob/b2e2cd5d0e0a0b4ef66034f37448292f012eb032/internal/mux/mux.go#L260-L287

[hajimehoshi]

Thanks. I'll tag v2.8.6 a few days later.