[PATCH RFC v2 03/10] locking/local_lock: Introduce localtry_lock_t

[Davidlohr Bueso]

On Wed, 26 Feb 2025, Alexei Starovoitov wrote:

>On Wed, Feb 26, 2025 at 9:01???AM Davidlohr Bueso <dave at stgolabs.net> wrote:
>>
>> On Fri, 14 Feb 2025, Vlastimil Babka wrote:
>>
>> >From: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
>> >
>> >In !PREEMPT_RT local_lock_irqsave() disables interrupts to protect
>> >critical section, but it doesn't prevent NMI, so the fully reentrant
>> >code cannot use local_lock_irqsave() for exclusive access.
>> >
>> >Introduce localtry_lock_t and localtry_lock_irqsave() that
>> >disables interrupts and sets acquired=1, so localtry_lock_irqsave()
>> >from NMI attempting to acquire the same lock will return false.
>> >
>> >In PREEMPT_RT local_lock_irqsave() maps to preemptible spin_lock().
>> >Map localtry_lock_irqsave() to preemptible spin_trylock().
>> >When in hard IRQ or NMI return false right away, since
>> >spin_trylock() is not safe due to PI issues.
>> >
>> >Note there is no need to use local_inc for acquired variable,
>> >since it's a percpu variable with strict nesting scopes.
>> >
>>
>> LGTM.
>>
>> Acked-by: Davidlohr Bueso <dave at stgolabs.net>
>
>Thanks for the review.
>Do you mind if I apply your ack to the latest version of this patch?
>https://lore.kernel.org/bpf/20250222024427.30294-2-alexei.starovoitov@gmail.com/

Yes, that is fine.

Thanks,
Davidlohr