linux-kernel - Re: [RFC] Make need_resched() return true when rcu_urgent

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Message-ID: <20180709130227.GQ2512@hirez.programming.kicks-ass.net>
Date:   Mon, 9 Jul 2018 15:02:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     David Woodhouse <dwmw2@...radead.org>, mhillenb@...zon.de,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] Make need_resched() return true when rcu_urgent_qs
 requested

On Mon, Jul 09, 2018 at 02:55:16PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 09, 2018 at 05:34:57AM -0700, Paul E. McKenney wrote:
> > But KVM defeats this by checking need_resched() before invoking
> > cond_resched().
> 
> That's not wrong or even uncommon I think.

In fact, I think we recently put that pattern in crypto code in order to
break up very long kernel_fpu sections.

Note that you also 'broke' cond_resched_lock() as that no longer matches
cond_resched().