On Sat, 2016-06-18 at 11:24 -0400, Jamal Hadi Salim wrote:
> On 16-06-18 11:16 AM, Eric Dumazet wrote:
>
> >> Given an update/replace of an action is such a rare occassion, what
> >> is wrong with init doing a spin lock on existing action?
> >> Sure, there is performance impact on fast path at tha
On 16-06-18 11:16 AM, Eric Dumazet wrote:
Given an update/replace of an action is such a rare occassion, what
is wrong with init doing a spin lock on existing action?
Sure, there is performance impact on fast path at that point - but:
as established update/replace is _a rare occassion_ ;->
The
On Sat, 2016-06-18 at 09:45 -0400, Jamal Hadi Salim wrote:
> On 16-06-17 06:03 PM, Eric Dumazet wrote:
> > On Fri, Jun 17, 2016 at 2:59 PM, Cong Wang wrote:
> >
> >> Generally speaking I worry about we change multiple fields in a struct
> >> meanwhile we could still read them any time in the middl
On 16-06-17 06:03 PM, Eric Dumazet wrote:
On Fri, Jun 17, 2016 at 2:59 PM, Cong Wang wrote:
Generally speaking I worry about we change multiple fields in a struct
meanwhile we could still read them any time in the middle, we may
get them correct for some easy case, but it is hard to insure the
On Fri, Jun 17, 2016 at 2:59 PM, Cong Wang wrote:
> Generally speaking I worry about we change multiple fields in a struct
> meanwhile we could still read them any time in the middle, we may
> get them correct for some easy case, but it is hard to insure the
> correctness when the struct becomes
On Fri, Jun 17, 2016 at 2:40 PM, Eric Dumazet wrote:
> On Fri, Jun 17, 2016 at 2:35 PM, Cong Wang wrote:
>> On Fri, Jun 17, 2016 at 2:24 PM, Eric Dumazet wrote:
>>> Well, I added a READ_ONCE() to read tcf_action once.
>>>
>>> Adding rcu here would mean adding a pointer and extra cache line, to
>
On Fri, Jun 17, 2016 at 2:35 PM, Cong Wang wrote:
> On Fri, Jun 17, 2016 at 2:24 PM, Eric Dumazet wrote:
>> Well, I added a READ_ONCE() to read tcf_action once.
>>
>> Adding rcu here would mean adding a pointer and extra cache line, to
>> deref the values.
>>
>> IMHO the race here has no effect .
On Fri, Jun 17, 2016 at 2:24 PM, Eric Dumazet wrote:
> Well, I added a READ_ONCE() to read tcf_action once.
>
> Adding rcu here would mean adding a pointer and extra cache line, to
> deref the values.
>
> IMHO the race here has no effect . You either read the old or new value.
Sure, the point is
On Fri, Jun 17, 2016 at 2:03 PM, Cong Wang wrote:
> Hi, Eric
>
> During code review, I notice we might have some problem after we go
> lockless for the fast path in act_mirred.
>
> That is, what prevents us from the following possible race condition?
>
> change a standalone action with tcf_mirred_
