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From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [GIT PULL] RCU changes for v5.10
Date: Mon, 19 Oct 2020 09:31:43 +0200	[thread overview]
Message-ID: <20201019073143.GA3785787@gmail.com> (raw)
In-Reply-To: <CAHk-=whE1rajA5Kzqey802zwv-82yrK5qc=nR3xRo5f38t-K8A@mail.gmail.com>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Mon, Oct 12, 2020 at 7:14 AM Ingo Molnar <mingo@kernel.org> wrote:
> >
> > Please pull the latest core/rcu git tree from:
> >
> >    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-rcu-2020-10-12
> 
> I've pulled everything but that last merge and the PREEMPT_COUNT 
> stuff that came with it.
> 
> When Paul asked whether it was ok for RCU to use preempt_count() and 
> I answered in the affirmative, I didn't mean it in the sense of "RCU 
> wants to force it on everybody else too".
>
> I'm pretty convinced that the proper fix is to simply make sure that 
> rcu_free() and friends aren't run under any raw spinlocks. So even 
> if the cost of preempt-count isn't that noticeable, there just isn't 
> a reason for RCU to say "screw everybody else, I want this" when 
> there are other alternatives.

That's certainly true - thanks for catching this & sorting it out from 
the bigger pull request!

Thanks,

	Ingo

      parent reply	other threads:[~2020-10-19  7:31 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12 14:14 [GIT PULL] RCU changes for v5.10 Ingo Molnar
2020-10-12 20:25 ` Linus Torvalds
2020-10-12 21:44   ` Paul E. McKenney
2020-10-12 21:59     ` Linus Torvalds
2020-10-12 23:54       ` Paul E. McKenney
2020-10-13  0:14         ` Linus Torvalds
2020-10-13  2:41           ` Paul E. McKenney
2020-10-13  7:32   ` Ingo Molnar
2020-10-13  9:16   ` Thomas Gleixner
2020-10-18 21:39 ` Linus Torvalds
2020-10-19  3:24   ` Paul E. McKenney
2020-10-19 16:51     ` Linus Torvalds
2020-10-19  7:31   ` Ingo Molnar [this message]

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