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



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.

    Stefan


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