On Mon, Jun 18, 2018 at 09:47 AM +0200, Erik Skultety <eskultet@xxxxxxxxxx> wrote:
> On Fri, Jun 15, 2018 at 03:31:34PM +0200, Marc Hartmayer wrote:
>> On Fri, Jun 15, 2018 at 01:39 PM +0200, Marc Hartmayer <mhartmay@xxxxxxxxxxxxx> wrote:
>> > If srv->workers is a NULL pointer, as it is the case if there are no
>> > workers, then don't try to dereference it.
>> >
>> > Signed-off-by: Marc Hartmayer <mhartmay@xxxxxxxxxxxxx>
>> > Reviewed-by: Boris Fiuczynski <fiuczy@xxxxxxxxxxxxx>
>> > ---
>> > src/rpc/virnetserver.c | 22 +++++++++++++++-------
>> > 1 file changed, 15 insertions(+), 7 deletions(-)
>> >
>> > diff --git a/src/rpc/virnetserver.c b/src/rpc/virnetserver.c
>> > index 5ae809e372..be6f610880 100644
>> > --- a/src/rpc/virnetserver.c
>> > +++ b/src/rpc/virnetserver.c
>> > @@ -933,13 +933,21 @@ virNetServerGetThreadPoolParameters(virNetServerPtr srv,
>> > size_t *jobQueueDepth)
>> > {
>> > virObjectLock(srv);
>> > -
>> > - *minWorkers = virThreadPoolGetMinWorkers(srv->workers);
>> > - *maxWorkers = virThreadPoolGetMaxWorkers(srv->workers);
>> > - *freeWorkers = virThreadPoolGetFreeWorkers(srv->workers);
>> > - *nWorkers = virThreadPoolGetCurrentWorkers(srv->workers);
>> > - *nPrioWorkers = virThreadPoolGetPriorityWorkers(srv->workers);
>> > - *jobQueueDepth = virThreadPoolGetJobQueueDepth(srv->workers);
>> > + if (srv->workers) {
>> > + *minWorkers = virThreadPoolGetMinWorkers(srv->workers);
>> > + *maxWorkers = virThreadPoolGetMaxWorkers(srv->workers);
>> > + *freeWorkers = virThreadPoolGetFreeWorkers(srv->workers);
>> > + *nWorkers = virThreadPoolGetCurrentWorkers(srv->workers);
>> > + *nPrioWorkers = virThreadPoolGetPriorityWorkers(srv->workers);
>> > + *jobQueueDepth = virThreadPoolGetJobQueueDepth(srv->workers);
>> > + } else {
>> > + *minWorkers = 0;
>> > + *maxWorkers = 0;
>> > + *freeWorkers = 0;
>> > + *nWorkers = 0;
>> > + *nPrioWorkers = 0;
>> > + *jobQueueDepth = 0;
>> > + }
>> >
>> > virObjectUnlock(srv);
>> > return 0;
>> > --
>> > 2.13.6
>>
>> After thinking again it probably makes more sense (and the code more
>> beautiful) to initialize the worker pool even for maxworker=0 (within
>
> I don't understand why should we do that. We don't even initialize it for
> libvirtd server - the implications are clear - you don't have workers, you
> don't get to process a job.
>
>> virNetServerNew) (=> we'll have to adapt virNetServerDispatchNewMessage
>> as well). BTW, there is also a segmentation fault in
>> virThreadPoolSetParameters… And currently it’s not possible to start
>> with maxworkers set to 0 and then increase it via
>
> Do I assume correctly that virNetServerDispatchNewMessage would allocate a new
> worker if there was a request to process but the threadpool was empty? If so, I
> don't see a reason to do that, why would anyone want to run with no workers?
> They don't consume any resources, since they're waiting on a condition.
> However, any segfaults or deadlocks must be fixed, I'll have a look at the
> series as is, unless you've got a compelling reason why it's beneficial to run
> with no workers at all.
Another problem/inconsistency in the current implementation is that if
you start with maxworkers=5 and then set the value to 0 via
virThreadPoolSetParameters (e.g. 'virt-admin server-threadpool-set
--min-workers 0 --max-workers 0 --priority-workers 0 libvirtd')
srv->workers still remains a non NULL value and the “thread pool memory
struct” still remains allocated and virNetServerDispatchNewMessage will
try to request a job… :)
>
> Thanks,
> Erik
>
--
Beste Grüße / Kind regards
Marc Hartmayer
IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294
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