Prevent hang on shutdown race.
This commit prevents a race that could happen on shutdown if a sigint was received between adding the first the interrupt handler and and future handlers. This code is loosely based on initial pull request #154 which was not accepted due to introducing a race of its own. Thanks to @tuxcanfly for the intial pull request and finding the issue.
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1 changed files with 25 additions and 2 deletions
27
signal.go
27
signal.go
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@ -24,11 +24,26 @@ func mainInterruptHandler() {
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// SIGINT (Ctrl+C) is received.
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var interruptCallbacks []func()
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// isShutdown is a flag which is used to indicate whether or not
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// the shutdown signal has already been received and hence any future
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// attempts to add a new interrupt handler should invoke them
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// immediately.
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var isShutdown bool
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for {
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select {
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case <-interruptChannel:
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// Ignore more than one shutdown signal.
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if isShutdown {
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btcdLog.Infof("Received SIGINT (Ctrl+C). " +
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"Already shutting down...")
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continue
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}
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isShutdown = true
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btcdLog.Infof("Received SIGINT (Ctrl+C). Shutting down...")
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// run handlers in LIFO order.
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// Run handlers in LIFO order.
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for i := range interruptCallbacks {
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idx := len(interruptCallbacks) - 1 - i
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callback := interruptCallbacks[idx]
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@ -36,9 +51,17 @@ func mainInterruptHandler() {
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}
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// Signal the main goroutine to shutdown.
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shutdownChannel <- struct{}{}
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go func() {
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shutdownChannel <- struct{}{}
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}()
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case handler := <-addHandlerChannel:
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// The shutdown signal has already been received, so
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// just invoke and new handlers immediately.
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if isShutdown {
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handler()
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}
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interruptCallbacks = append(interruptCallbacks, handler)
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}
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}
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