Try to use sync.RWMutex instead, you have more control when to read or
write.
Em sáb, 26 de jun de 2021 18:34, 'Dan Kortschak' via golang-nuts <
golang-nuts@googlegroups.com> escreveu:
> On Sat, 2021-06-26 at 23:26 +0100, Rory Campbell-Lange wrote:
> > I'm trying to work out why I have a data race problem (on go 1.15 and
> > 1.16).
> >
> > *SearchResults.Set is called from several goroutines. I am trying to
> > avoid concurrent access to its two maps using a mutex, but this isn't
> > working.
> >
> > 108 type SearchResults struct {
> > 109 Boxes map[string][]Box
> > 110 seen map[string]bool
> > 111 sync.Mutex
> > 112 }
> > 113
> > 114 // Set adds a new box to the search results map
> > 115 func (s *SearchResults) Set(b Box) {
> > 116
> > 117 s.Lock()
> > 118 defer s.Unlock()
> > 119
> > 120 if _, ok := s.seen[b.BoxID]; ok { // race problem
> > 121 return
> > 122 }
> > 123
> > 124 if model := b.GetModel(); model != "" {
> > 125 s.Boxes[model] = append(s.Boxes[model], b) // race
> > problem
> > 126 s.seen[b.BoxID] = true // race problem
> > 127 }
> > 128 }
> >
> > The data race report from go run -race <program> shows
> >
> > ==================
> > WARNING: DATA RACE
> > Write at 0x00c000012e70 by goroutine 16:
> > runtime.mapassign_faststr()
> > /home/rory/bin/go/src/runtime/map_faststr.go:202 +0x0
> > main.(*SearchResults).Set()
> > /home/rory/src/go-cex/cexer.go:126 +0x345
> > ...
> > Previous read at 0x00c000012e70 by goroutine 8:
> > runtime.mapaccess2_faststr()
> > /home/rory/bin/go/src/runtime/map_faststr.go:107 +0x0
> > main.(*SearchResults).Set()
> > /home/rory/src/go-cex/cexer.go:120 +0xf6
> > ...
> > ==================
> > WARNING: DATA RACE
> > Read at 0x00c000012ea0 by goroutine 8:
> > runtime.mapaccess1_faststr()
> > /home/rory/bin/go/src/runtime/map_faststr.go:12 +0x0
> > main.(*SearchResults).Set()
> > /home/rory/src/go-cex/cexer.go:125 +0x195
> > ...
> > Previous write at 0x00c000012ea0 by goroutine 16:
> > runtime.mapassign_faststr()
> > /home/rory/bin/go/src/runtime/map_faststr.go:202 +0x0
> > main.(*SearchResults).Set()
> > /home/rory/src/go-cex/cexer.go:125 +0x2a7
> > ...
> >
> > Advice gratefully received.
> >
> > Rory
>
> It looks like the Box type is being mutated and read in more than one
> goroutine; you're protecting Set, but is the b value being used
> elsewhen?
>
> Dan
>
>
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>
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