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Re: [Qemu-devel] Re: [PATCH 10/22] migration: Refactor and simplify erro
From: |
Yoshiaki Tamura |
Subject: |
Re: [Qemu-devel] Re: [PATCH 10/22] migration: Refactor and simplify error checking in migrate_fd_put_ready |
Date: |
Wed, 23 Feb 2011 20:36:20 +0900 |
2011/2/23 Juan Quintela <address@hidden>:
> Yoshiaki Tamura <address@hidden> wrote:
>> 2011/2/23 Juan Quintela <address@hidden>:
>>>
>>> Signed-off-by: Juan Quintela <address@hidden>
>>> ---
>>> migration.c | 20 +++++++++-----------
>>> 1 files changed, 9 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/migration.c b/migration.c
>>> index f015e02..641df9f 100644
>>> --- a/migration.c
>>> +++ b/migration.c
>>> @@ -361,28 +361,26 @@ static void migrate_fd_put_ready(void *opaque)
>>>
>>> DPRINTF("iterate\n");
>>> if (qemu_savevm_state_iterate(s->mon, s->file) == 1) {
>>> - int state;
>>> int old_vm_running = vm_running;
>>>
>>> DPRINTF("done iterating\n");
>>> vm_stop(VMSTOP_MIGRATE);
>>>
>>> - if ((qemu_savevm_state_complete(s->mon, s->file)) < 0) {
>>> - if (old_vm_running) {
>>> - vm_start();
>>> - }
>>> - state = MIG_STATE_ERROR;
>>> + if (qemu_savevm_state_complete(s->mon, s->file) < 0) {
>>> + migrate_fd_error(s);
>>> } else {
>>> - state = MIG_STATE_COMPLETED;
>>> + if (migrate_fd_cleanup(s) < 0) {
>>> + migrate_fd_error(s);
>>> + } else {
>>> + s->state = MIG_STATE_COMPLETED;
>>> + notifier_list_notify(&migration_state_notifiers);
>>> + }
>>> }
>>> - if (migrate_fd_cleanup(s) < 0) {
>>> + if (s->get_status(s) != MIG_STATE_COMPLETED) {
>>> if (old_vm_running) {
>>> vm_start();
>>> }
>>
>> This part, although it's not fair to ask you, but calling
>> vm_start when != MIG_STATE_COMPLETED terrifies me because just
>> failing migrate_fd_cleanup (mostly calling qemu_fclose) may cause
>> split brain between src/dst. Although I haven't encountered this
>> situation, just having stopped VMs on both sides is safer.
>
> I see your pain. I am not happy at all, but this was integrated by
> Anthony to fix this bug:
>
> commit 41ef56e61153d7bd27d34a634633bb51b1c5988d
> Author: Anthony Liguori <address@hidden>
> Date: Wed Jun 2 14:55:25 2010 -0500
>
> migration: respect exit status with exec:
>
> This fixes https://bugs.launchpad.net/qemu/+bug/391879
>
Thanks for the link. I don't know IIUC, why stopping the VM was
a problem? The essential thing is that we need to introduce a
flag that whether user wants to continue a VM when something goes
wrong during live migration. Deciding only with old_vm_running is
wrong.
> I think that it fixes that bug, but it makes me un-easy to restart vm if
> there is a failure in migrate_fd_cleanup(). As I didn't wanted to
> change behaviour with this series, I left it as it was.
I agree with keeping the behavior unchanged.
> Next on ToDo list is to do something sensible with errors, just now we
> are not very good at handling them.
Yeah. If we introduce Kemari, the migration code becomes more
important because it'll be part of the normal VM execution
path :)
Thanks,
Yoshi
>
> Later, Juan.
>
>
- Re: [Qemu-devel] [PATCH 06/22] migration: Make all posible migration functions static, (continued)
- [Qemu-devel] [PATCH 11/22] migration: Introduce migrate_fd_completed() for consistenncy, Juan Quintela, 2011/02/22
- [Qemu-devel] [PATCH 12/22] migration: Use migrate_fd_error() in last place that set status to ERROR, Juan Quintela, 2011/02/22
- [Qemu-devel] [PATCH 13/22] migration: Our release callback was just free, Juan Quintela, 2011/02/22
- [Qemu-devel] [PATCH 15/22] migration: Remove migration cancel() callback, Juan Quintela, 2011/02/22
- [Qemu-devel] [PATCH 14/22] migration: Remove get_status() accessor, Juan Quintela, 2011/02/22
- [Qemu-devel] [PATCH 16/22] migration: Move exported functions to the end of the file, Juan Quintela, 2011/02/22