From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: jolsa@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: Folllowing up on LSF/MM RCU/idle discussion
Date: Tue, 10 May 2022 08:54:57 +0200 [thread overview]
Message-ID: <20220510065457.GI76023@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220509155633.GA93071@paulmck-ThinkPad-P17-Gen-1>
On Mon, May 09, 2022 at 08:56:33AM -0700, Paul E. McKenney wrote:
> Hello, Jiri!
>
> It was good chatting with you last week, and I hope that travels went
> well!
>
> Just wanted to follow up on the non-noinstr code between the call
> to rcu_idle_enter() and rcu_idle_exit(). Although the most correct
> approach is to never have non-noinstr code in arch_cpu_idle(), for all I
> know there might well be architectures for which this is not feasible.
> If so, one workaround would be to supply a flag set by each arch (or
> subarch) that says that rcu_idle_enter() and rcu_idle_exit() are invoked
> within arch_cpu_idle().
>
> CCing Peter, who just might have an opinion on this. ;-)
Definitely have an opinion; just lack the tools to enforce these rules.
I cleaned up the worst of it for x86 but it's a shit-show for most
others. ARM in particular has some 'issues'.
But yeah, noinstr only when you do rcu_idle_enter.
The problem with validating all this is that cpuidle is a rats nest of
indirect calls; in order to validate the noinstr'ness of something like
that we need compiler support for pointer address spaces such that we
can stick pointers to noinstr functions in a different address space and
get complaints etc..
next prev parent reply other threads:[~2022-05-10 6:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-09 15:56 Folllowing up on LSF/MM RCU/idle discussion Paul E. McKenney
2022-05-10 6:54 ` Peter Zijlstra [this message]
2022-05-10 9:43 ` Mark Rutland
2022-05-10 15:55 ` Paul E. McKenney
2022-05-10 16:19 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220510065457.GI76023@worktop.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=paulmck@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).