Re: [Qemu-devel] [RFC 0/7] Safe watch and breakpoint manipulation

[Sergey Fedorov]

On 17/06/16 20:01, Paolo Bonzini wrote:
>
> On 17/06/2016 18:33, Alex Bennée wrote:
>> First we move the break/watchpoints into an array which is more
>> amenable to RCU control that the QLIST. We then control the life time
>> of references to break/watchpoint data by removing long held
>> references in the target code and getting information when needed from
>> the core. Then we stop dynamically allocation the watch/breakpoint
>> data and store it directly in the array which makes iteration across
>> the list a bit more cache friendly than referenced pointers. Finally
>> addition and removal of elements of the array is put under RCU
>> control. This ensures there is always a safe array of data to check
>> in the run-loop.
> I'm not sure why you say that arrays are more amenable than QTAILQ
> (though indeed include/qemu/rcu_queue.h only includes QLIST for now),
> but I feel bad asking you to redo all the work...

Is there any realistic way to manage *doubly* linked lists in RCU?

Kind regards,
Sergey