linux-kernel - Re: [PATCH RFC v2 rcu 2/8] srcu: Create an srcu_read_lock_nmisafe() and srcu_read_unlock

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Message-ID: <20221002161049.GQ4196@paulmck-ThinkPad-P17-Gen-1>
Date:   Sun, 2 Oct 2022 09:10:49 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, rostedt@...dmis.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Ogness <john.ogness@...utronix.de>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH RFC v2 rcu 2/8] srcu: Create an srcu_read_lock_nmisafe()
 and srcu_read_unlock_nmisafe()

On Sun, Oct 02, 2022 at 05:57:25PM +0200, Frederic Weisbecker wrote:
> On Sun, Oct 02, 2022 at 05:55:16PM +0200, Frederic Weisbecker wrote:
> > On Thu, Sep 29, 2022 at 11:07:25AM -0700, Paul E. McKenney wrote:
> > > @@ -1090,7 +1121,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
> > >  	int ss_state;
> > >  
> > >  	check_init_srcu_struct(ssp);
> > > -	idx = srcu_read_lock(ssp);
> > > +	idx = __srcu_read_lock_nmisafe(ssp);
> > 
> > Why do we need to force the atomic based version here (even if
> > CONFIG_NEED_SRCU_NMI_SAFE=y)?
> 
> ...even if CONFIG_NEED_SRCU_NMI_SAFE=n that is...

Heh!  I also got it consistently backwards in my reply.  I will trust
your ability to translate.  ;-)

							Thanx, Paul