[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]
Re: struct ifnet and ifaddr handling [was: Re: Making global variables of if.c MPSAFE]
On Thu, Nov 13, 2014 at 1:26 PM, Taylor R Campbell
> Date: Thu, 13 Nov 2014 12:43:26 +0900
> From: Ryota Ozaki <ozaki-r%netbsd.org@localhost>
> Here is a new patch: http://www.netbsd.org/~ozaki-r/psz-ifnet.diff
> I think the patch reflects rmind's suggestions:
> - Use pserialize for IFNET_FOREACH
> - but use a lock for blockable/sleepable critical sections
> - cpu_intr_p workaround for HW interrupt
> Any comments?
> Hmm...some quick notes from a non-expert in sys/net:
> - You call malloc(M_WAITOK) while the ifnet lock is held, in
> if_alloc_sadl_locked, which is not allowed.
Oh, I didn't know that restriction. LOCKDEBUG didn't correct me...
> - You call copyout in a pserialize read section, in ifconf, which is
> not allowed because copyout may block.
Which one? I think I've fixed such usages this time.
> - I don't know what cpu_intr_p is working around but it's probably not
> a good idea!
Yes :-| We have to fix that in the future, but it works as same as it is
until we get rid of all KERNE_LOCK.
> Generally, all that you are allowed to do in a pserialize read section
> is read a small piece of information, or grab a reference to a data
> structure which you are then going to use outside the read section.
Yes. I'm implementing a facility of the latter for ifunit:
> I don't think it's going to be easy to scalably parallelize this code
> without restructuring it, unless as a stop-gap you use a heaver-weight
> reader-writer lock like the prwlock at
> (No idea how much overhead this might add.)
Could you elaborate how to use it?
Main Index |
Thread Index |