On Mon, Jun 18, 2018 at 09:47 AM +0200, Erik Skultety <eskultet@redhat.com> 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@linux.ibm.com> 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@linux.ibm.com> Reviewed-by: Boris Fiuczynski <fiuczy@linux.ibm.com> --- 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.
Because right now there are several functionalities broken. Segmentation faults in virNetServerGet/SetThreadPoolParameters, it’s not possible to start with maxworkers=0 and then change it at runtime via virNetServerSetThreadPoolParameters. Sure we can fix all these problems, but then we’ve to introduce new code paths. Why can’t we just call virThreadPoolNew(0, 0 , …)? This will only initialize the memory structure of the pool and _no_ threads. The only change we’ve to do then is to change the condition 'if (srv->workers)' of 'virNetServerDispatchNewMessage' to something like 'if (virThreadPoolGetMaxWorkers(srv->workers) > 0)'.
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.
Yep. I don’t want to change that behavior either.
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?
Do you mean with my proposed changes? Or without?
If so, I don't see a reason to do that, why would anyone want to run with no workers?
Commit dff6d809fb6c851244ea07afd07f580d7320cc7a which actually introduces this feature says: “Allow RPC server to run single threaded Refactor the RPC server dispatcher code so that if 'max_workers==0' the entire server will run single threaded. This is useful for use cases where there will only ever be 1 client connected which serializes its requests”.
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.
See the commit message above.
Thanks, Erik
Thank you for looking at it. -- 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