On Thu, Mar 04 2021 at 09:11, Sebastian Andrzej Siewior wrote:
> On 2021-03-03 16:09:05 [-0600], Eric W. Biederman wrote:
>> Sebastian Andrzej Siewior <bige...@linutronix.de> writes:
>>
>> > From: Thomas Gleixner <t...@linutronix.de>
>> >
>> > Allow realtime tasks to cache one sigqueue in task struct. This avoids an
>> > allocation which can increase the latency or fail.
>> > Ideally the sigqueue is cached after first successful delivery and will be
>> > available for next signal delivery. This works under the assumption that
>> > the RT
>> > task has never an unprocessed signal while a one is about to be queued.
>> >
>> > The caching is not used for SIGQUEUE_PREALLOC because this kind of
>> > sigqueue is
>> > handled differently (and not used for regular signal delivery).
>>
>> What part of this is about real time tasks? This allows any task
>> to cache a sigqueue entry.
>
> It is limited to realtime tasks (SCHED_FIFO/RR/DL):
>
> +static void __sigqueue_cache_or_free(struct sigqueue *q)
> +{
> …
> + if (!task_is_realtime(current) || !sigqueue_add_cache(current, q))
> + kmem_cache_free(sigqueue_cachep, q);
> +}
We could of course do the caching unconditionally for all tasks.
Thanks,
tglx
