Re: [libvirt] [BUG?] EAGAIN not triggering error and 'events' gets cleared
On Tue, Apr 28, 2015 at 11:24:37 +0200, Michal Privoznik wrote: On 28.04.2015 11:06, Pavel Boldin wrote: 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. Yep, this is known bug. I've told Peter already like two weeks ago. He promised to fix it. It would be nice if we can get the fix into the release. There are already patches for the issue: http://www.redhat.com/archives/libvir-list/2015-April/msg00724.html signature.asc Description: Digital signature -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [BUG?] EAGAIN not triggering error and 'events' gets cleared
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 pbol...@mirantis.com 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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Re: [libvirt] [BUG?] EAGAIN not triggering error and 'events' gets cleared
On 28.04.2015 11:06, Pavel Boldin wrote: 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. Yep, this is known bug. I've told Peter already like two weeks ago. He promised to fix it. It would be nice if we can get the fix into the release. Michal -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
Re: [libvirt] [BUG?] EAGAIN not triggering error and 'events' gets cleared
Thanks Peter, It looks good but I did no deep introspection of the code. Should I rebase my patch [1] on that? I can test your code as well then. [1] https://github.com/paboldin/libvirt/commits/master Pavel On Tue, Apr 28, 2015 at 4:42 PM, Peter Krempa pkre...@redhat.com wrote: On Tue, Apr 28, 2015 at 11:24:37 +0200, Michal Privoznik wrote: On 28.04.2015 11:06, Pavel Boldin wrote: 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. Yep, this is known bug. I've told Peter already like two weeks ago. He promised to fix it. It would be nice if we can get the fix into the release. There are already patches for the issue: http://www.redhat.com/archives/libvir-list/2015-April/msg00724.html -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
[libvirt] [BUG?] EAGAIN not triggering error and 'events' gets cleared
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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