Messages in this thread | | | Date | Wed, 8 Jul 2020 14:08:33 +0100 | From | Qais Yousef <> | Subject | Re: [PATCH v6 1/2] sched/uclamp: Add a new sysctl to control RT default boost value |
| |
On 07/08/20 12:05, Valentin Schneider wrote: > > AFAIU rcu_read_lock() is light weight. So having the protection applied is more > > robust against future changes. > > So I think the one thing you win by having this dance with mb's and the > suggested handling of the task list is that you do not need any > rcu_synchronize() anymore. Both approaches have merit, it's just that the > way I understood the suggestion to add sched_post_fork() was to simplify > the ordering of the update with the aforementioned scheme.
The synchronize_rcu() is not for sched_post_fork(). It is to deal with the preemption problem.
> > > > >> > >> sched_post_fork() being preempted out is a bit more annoying, but what > >> prevents us from making that bit preempt-disabled? > > > > preempt_disable() is not friendly to RT and heavy handed approach IMO. > > > > True, but this is both an infrequent and slow sysctl path, so I don't think > RT would care much.
There's an easy answer for that. But first I'm not sure what problem are we discussing here.
What is the problem with rcu? And how is preempt_disable() fixes it or improves on it?
Thanks
-- Qais Yousef
| |