Re: [PATCHv2/RFC] kvm/irqchip: Speed up KVM_SET_GSI_ROUTING

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 16/01/14 13:59, Paolo Bonzini wrote:
> Il 16/01/2014 13:44, Christian Borntraeger ha scritto:
>> I converted most of the rcu routines to srcu. Review for the unconverted
>> use of hlist_for_each_entry_rcu, hlist_add_head_rcu, hlist_del_init_rcu
>> is necessary, though. They look fine to me since they are protected by
>> outer functions.
> 
> They are fine because they do not have lockdep checks
> (hlist_for_each_entry_rcu uses rcu_dereference_raw rather than
> rcu_dereference, and write-sides do not do rcu lockdep at all).
> 
>> In addition, we should also discuss if a global srcu (for all guests) is
>> fine.
> 
> I think it is.  It is already way cheaper than it used to be, and we're
> hardly relying on the "sleepable" part of srcu.  We just want its faster
> detection of grace periods.  One instance should be fine because our
> read sides are so small and mostly they are not even preemptable.
> 
> Thanks for writing the patch!
> 
> Paolo
> 

Will you edit the patch description or shall I resend the patch?