Re: [libvirt] [PATCH 2/6] virObject: Introduce virObjectRecursiveLockableNew

On 02/16/2018 09:34 AM, Pavel Hrdina wrote: > On Mon, Feb 12, 2018 at 01:16:28PM +0100, Michal Privoznik wrote: >> On 02/12/2018 01:10 PM, Peter Krempa wrote: >>> On Mon, Feb 12, 2018 at 11:52:49 +0100, Michal Privoznik wrote: >>>> Sometimes we need the lock in virObjectLockable to be recursive. >>>> Because of the nature of pthreads we don't need a special class >>>> for that - the pthread_* APIs don't distinguish between normal >>>> and recursive locks. >>>> >>>> Based-on-work-of: John Ferlan <jferlan(a)redhat.com&gt; >>>> Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; >>>> --- >>>> src/libvirt_private.syms | 1 + >>>> src/util/virobject.c | 22 +++++++++++++++++++--- >>>> src/util/virobject.h | 4 ++++ >>>> 3 files changed, 24 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms >>>> index 3b14d7d15..fcf378105 100644 >>>> --- a/src/libvirt_private.syms >>>> +++ b/src/libvirt_private.syms

This can be viewed as rewrite of existing code, not completely new code. > > I know that NWFilter code is complex and removing recursive locks is > not an easy task, but for the long run I think it's worth it, it will > make the code cleaner and easier to follow. Right, that the ideal goal. But as I said it's far from happening. I think it was you who when trying to fix some issue in NWFilter drew call graph in NWFilter driver and realized how complicated it is. That's why I don't see it happening anywhere in near future. Also, if we really have multiple entry points as Dan mentioned earlier can we really fix this? I mean there are multiple locks that need to be acquired when touching a virNWFilterObj. The advantage of reentrant mutex is that we will not get a dead lock scenario if two functions fight over lock. Anyway, it's a pity that we are stuck on this patch while reworking the vir*ObjList code.