De-race CompleteSync (#2601)

neilalexander · web-flow · commit e94ef84aaba3 · 2022-08-01T15:55:56.000+01:00
The `err` was coming from outside of the goroutine and being written to by concurrent goroutines.
diff --git a/syncapi/streams/stream_pdu.go b/syncapi/streams/stream_pdu.go
@@ -109,12 +109,11 @@ func (p *PDUStreamProvider) CompleteSync(
 		p.queue(func() {
 			defer reqWaitGroup.Done()
 
-			var jr *types.JoinResponse
-			jr, err = p.getJoinResponseForCompleteSync(
+			jr, jerr := p.getJoinResponseForCompleteSync(
 				ctx, roomID, r, &stateFilter, &eventFilter, req.WantFullState, req.Device,
 			)
-			if err != nil {
-				req.Log.WithError(err).Error("p.getJoinResponseForCompleteSync failed")
+			if jerr != nil {
+				req.Log.WithError(jerr).Error("p.getJoinResponseForCompleteSync failed")
 				return
 			}
 

Original file line number	Diff line number	Diff line change
`@@ -109,12 +109,11 @@ func (p *PDUStreamProvider) CompleteSync(`
`109`	`109`	`p.queue(func() {`
`110`	`110`	`defer reqWaitGroup.Done()`
`111`	`111`
`112`		`- var jr *types.JoinResponse`
`113`		`- jr, err = p.getJoinResponseForCompleteSync(`
	`112`	`+ jr, jerr := p.getJoinResponseForCompleteSync(`
`114`	`113`	`ctx, roomID, r, &stateFilter, &eventFilter, req.WantFullState, req.Device,`
`115`	`114`	`)`
`116`		`- if err != nil {`
`117`		`- req.Log.WithError(err).Error("p.getJoinResponseForCompleteSync failed")`
	`115`	`+ if jerr != nil {`
	`116`	`+ req.Log.WithError(jerr).Error("p.getJoinResponseForCompleteSync failed")`
`118`	`117`	`return`
`119`	`118`	`}`
`120`	`119`