[libvirt] [PATCH 3/5] Push nwfilter update locking up to top level

Stefan Berger stefanb at linux.vnet.ibm.com
Mon Jan 27 18:05:51 UTC 2014

On 01/27/2014 12:15 PM, Daniel P. Berrange wrote:
> On Thu, Jan 23, 2014 at 04:13:57PM -0500, Stefan Berger wrote:
>> This function here is called by
>> src/nwfilter/nwfilter_learnip.c::learnIPAddressThread
>> src/nwfilter/nwfilter_dhcpsnoop.c::virNWFilterSnoopIPLeaseInstallRule
>> They instantiate the filters once a VM's IP address has been
>> detected. So this is where the *Late() comes from.
>> If you remove the locking from here, you have to lock it there.
>> Considering what you do layer, I would keep the lock here and
>> convert this into a reader lock layer on.
> Yes, now I'm squashing the read/write lock conversion in, I'll
> keep the locking in this location.

Is there interest in introducing an assert() in those functions 
expecting a lock to be held? I know it's not as simple as just putting 
an assert() into the code. Actually we would have to record in an array 
or linked list the threads holding a lock and provide a function to 
check whether pthread_self() is holding the lock. The latter function 
would be called by an assert(). I would give it a shot by introducing a 
boolean as parameter to the lock init function that activates the 
recording of which threads are currently holding a lock -- if this is 
thought to be useful.


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