[libvirt] [BUG?] EAGAIN not triggering error and 'events' gets cleared

[Pavel Boldin]

Dear Libvirt Developers,

There seems to be a bug or at least a bad behavior in
`src/qemu/qemu_monitor.c' lines 683-689 function `qemuMonitorIO':

            if (qemuMonitorIOWrite(mon) < 0) {
                error = true;
                if (errno == ECONNRESET)
                    hangup = true;
            }
            events &= ~VIR_EVENT_HANDLE_WRITABLE;

The `qemuMonitorIOWrite' is returning 0 in case 'write' returns EAGAIN thus
'events' is always cleared of `VIR_EVENT_HANDLE_WRITABLE' even in case no
message have been sent indeed.

The question is: who is responsible for handling this? It seems like
'errno' is getting overwritten inside all of qemuMonitorJSON* functions so
the caller can't rely on it and it needs to be fixed inside the
`qemuMonitorIO'.

Pavel
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