Klaus Post 0de2b9a1b2 Fix panic on double unfreezeServices (#18177) ...

Calling unfreezeServices twice results in panic:

```
panic: "POST /minio/peer/v32/signalservice?signal=4&sub-sys=": close of nil channel
goroutine 14703 [running]:
runtime/debug.Stack()
	runtime/debug/stack.go:24 +0x65
github.com/minio/minio/cmd.setCriticalErrorHandler.func1.1()
	github.com/minio/minio/cmd/generic-handlers.go:549 +0x8e
panic({0x27c3020, 0x4c9b370})
	runtime/panic.go:884 +0x212
github.com/minio/minio/cmd.unfreezeServices()
	github.com/minio/minio/cmd/service.go:112 +0xc7
github.com/minio/minio/cmd.(*peerRESTServer).SignalServiceHandler(0x0?, {0x4cb6af0, 0xc010b96420}, 0xc01affab00)
	github.com/minio/minio/cmd/peer-rest-server.go:837 +0x13a
net/http.HandlerFunc.ServeHTTP(...)
```

If the function was called a second time `val` would not be nil, but the returned channel `ch` would be, causing the panic.

Check the channel isn't nil and also use Swap for an atomic swap instead of 2 separate operations (though we are in a mutex).

2023-10-06 07:51:50 -06:00

3.9 KiB

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