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

[Pavel Boldin <pboldin@xxxxxxxxxxxx>]

Well, actually that seems to be quite a different bug in there.

I will start a new thread.

In short: migration seems to be broken by commit 1a92c719101e5bfa6fe2b78006ad04c7f075ea28. This is because introduced job _MODIFY waits while MIGRATION_OUT is finished to change `mirrorState' variable. This deadlocks the libvirt.

Pavel

On Tue, Apr 28, 2015 at 6:29 AM, Pavel Boldin <pboldin@xxxxxxxxxxxx> wrote:

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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