Re: [PATCH bpf-next v5 2/5] bpf: Add sleepable support for classic tracepoint programs

[Mykyta Yatsenko <mykyta.yatsenko5@gmail.com>]

Mykyta Yatsenko <mykyta.yatsenko5@gmail.com> writes:

> On 3/23/26 9:26 PM, oskar@gerlicz.space wrote:
>>> +       if (unlikely(this_cpu_inc_return(bpf_prog_active) != 1)) {
>> 
>> Hi,
>> 
>> A question regarding the recursion handling.
>> 
>> Even with migrate_disable(), this still runs in a preemptible and
>> sleepable context. So if a task increments bpf_prog_active and then
>> sleeps, another task could run on the same CPU and also modify the
>> same per-CPU counter.
>> 
>> Would this interleaving affect recursion tracking correctness, or is
>> this accounted for?
>> 
>> Oskar Gerlicz Kowalczuk
>> 
> We discussed this with Kumar in the sibling thread, the initial thinking 
> behind this was that second task incrementing this counter won't see 1, 
> so it's going to
>
> this_cpu_dec(bpf_prog_active);
> return 0;
>
> I'm reworking this for the next version.
The initial thinking behind this was that the second task incrementing this counter won't see 1, so it's going to

this_cpu_dec(bpf_prog_active);
return 0;

I'm reworking this for the next version, as discussed in the sibling thread with Kumar.