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doc: race condition in unsynchronized send/close
This CL documents that unsynchronized send and close operations on a channel are detected as a race condition. Fixes #27769 Change-Id: I7495a2d0dd834c3f3b6339f8ca18ea21ae979aa8 Reviewed-on: https://go-review.googlesource.com/c/go/+/219637 Reviewed-by: Rob Pike <r@golang.org>
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@ -379,6 +379,38 @@ func (w *Watchdog) Start() {
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}
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</pre>
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<h3 id="Unsynchronized_send_and_close_operations">Unsynchronized send and close operations</h3>
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<p>
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As this example demonstrates, unsynchronized send and close operations
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on the same channel can also be a race condition:
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</p>
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<pre>
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c := make(chan struct{}) // or buffered channel
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// The race detector cannot derive the happens before relation
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// for the following send and close operations. These two operations
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// are unsynchronized and happen concurrently.
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go func() { c <- struct{}{} }()
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close(c)
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</pre>
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<p>
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According to the Go memory model, a send on a channel happens before
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the corresponding receive from that channel completes. To synchronize
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send and close operations, use a receive operation that guarantees
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the send is done before the close:
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</p>
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<pre>
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c := make(chan struct{}) // or buffered channel
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go func() { c <- struct{}{} }()
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<-c
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close(c)
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</pre>
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<h2 id="Supported_Systems">Supported Systems</h2>
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<p>
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