On 28.08.2017 17:55, Jiri Denemark wrote:
> On Thu, Aug 24, 2017 at 09:56:40 +0300, Nikolay Shirokovskiy wrote:
>> Current code consults job.current->stats.status to check for postcopy
>> state. First it is more correct to check for both job.current->status
>> and job.current->stats.status.code because on some paths on failures
>> we change only the former. Second if qemu supports migration events
>> then stats can change unexpectedly.
>
> I'm not sure I understand what you're trying to say. Could you explain
> this a bit more?
This place looks dangerous to me:
@@ -3836,7 +3840,7 @@ qemuMigrationRun(virQEMUDriverPtr driver,
else if (rc == -1)
goto cleanup;
- if (priv->job.current->stats.status ==
QEMU_MONITOR_MIGRATION_STATUS_POSTCOPY)
+ if (priv->job.current->status == QEMU_DOMAIN_JOB_STATUS_POSTCOPY)
inPostCopy = true;
It makes decisions based on current state of migration and consult stats.status
for
this purpose. Such a check can be mistaken because in the code above this hunk
if error occurs we change only current->status
value. Also after patch 6 we can update stats.status during fetching migrations
stats but not change current->status.
However in a more detail analysis it looks like this code do not have undesired
effects and only look dangerous (at least to me). So I guess I'd better say it
is easier
to reason about if we have postcopy as one of the status states.
>
>> Let's introduce QEMU_DOMAIN_JOB_STATUS_POSTCOPY state for
>> job.current->status.
>>
>> This patch removes all state checking usage of stats except for
>> qemuDomainGetJobStatsInternal. This place will be handled separately.
>> ---
>> src/qemu/qemu_domain.c | 1 +
>> src/qemu/qemu_domain.h | 1 +
>> src/qemu/qemu_driver.c | 5 +++--
>> src/qemu/qemu_migration.c | 18 +++++++++++-------
>> src/qemu/qemu_process.c | 4 ++--
>> 5 files changed, 18 insertions(+), 11 deletions(-)
>
> ACK
>
> Jirka
>
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