Re: [PATCH v2 5/9] bpf: simplify callback inuse tracking to boolean flag

[Marat Khalili <qm2k21@gmail.com>]

On 19/10/2026 21:50, Konstantin Ananyev wrote:
>> The even/odd usage counter semantics in struct bpf_eth_cbi was
>> originally used to detect when in-flight packet callbacks complete.
>> However, with at most one thread running the callback per port/queue
>> pair and no risk of the ABA problem, a boolean flag (true for in use,
>> false for idle) suffices.
>>
>> Change member use to bool and replace the counter increment in the
>> datapath with stores of true and false. Simplify bpf_eth_cbi_wait()
>> to a direct pause loop waiting until the flag is false, removing the
>> now unnecessary RTE_WAIT_UNTIL_MASKED macro and casts. Update the
>> documentation and synchronization sequence diagram accordingly.
>
> As I explained in previous mail, it is not about even/odd.
> It is about waiting while current 'quiscent' period will end.
> By 'simplifying' that to use just boll values (0/1) you introduce
> a live-lock in CP: it can be blocked for very long time waiting
> while DP thread will keep processing packets.

I do not think this explanation is correct. It was always waiting only 
for the next value after the odd one, there are no cases where anything 
else happens.