Re: [patch 1/2] mm: protect local lock sections with rcu_read_lock (on RT)

Nicolas Saenz Julienne
2022-02-22T15:21:32Z

On Tue, 2022-02-22 at 11:47 -0300, Marcelo Tosatti wrote:
> For the per-CPU LRU page vectors, augment the local lock protected
> code sections with rcu_read_lock.
>
> This makes it possible to replace the queueing of work items on all
> CPUs by synchronize_rcu (which is necessary to run FIFO:1 applications
> uninterrupted on isolated CPUs).

I don't think this is needed. In RT local_locks use a spinlock. See
kernel/locking/spinlock_rt.c:

"The RT [spinlock] substitutions explicitly disable migration and take
rcu_read_lock() across the lock held section."

Regards,

--
Nicolás Sáenz