Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> writes:
> On Thu, Oct 21, 2021 at 11:40 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
>> + map_type = READ_ONCE(array->aux->type);
>> + if (!map_type) {
>> + /* There's no owner yet where we could check for compatibility.
>> + * Do an atomic swap to prevent racing with another invocation
>> + * of this branch (via simultaneous map_update syscalls).
>> */
>> - array->aux->type = fp->type;
>> - array->aux->jited = fp->jited;
>> + if (cmpxchg(&array->aux->type, 0, prog_type))
>> + return false;
>
> Other fields might be used in the compatibility check in the future.
> This hack is too fragile.
> Just use a spin_lock.
Well, yeah, we're adding another field for xdp_mb. I was just going to
eat more bits of the 'type' field, but OK, can switch to a spinlock
instead :)
-Toke
