linux-kernel - Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs functions

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Message-ID: <20220519214303.GC6479@worktop.programming.kicks-ass.net>
Date:   Thu, 19 May 2022 23:43:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Phil Auld <pauld@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu Liao <liaoyu15@...wei.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Uladzislau Rezki <uladzislau.rezki@...y.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 03/21] rcu: Add a note about noinstr VS unsafe eqs
 functions

On Thu, May 19, 2022 at 05:00:26PM +0200, Peter Zijlstra wrote:
> On Tue, May 03, 2022 at 12:00:33PM +0200, Frederic Weisbecker wrote:
> > @@ -895,6 +899,10 @@ static void noinstr rcu_eqs_exit(bool user)
> >   *
> >   * If you add or remove a call to rcu_idle_exit(), be sure to test with
> >   * CONFIG_RCU_EQS_DEBUG=y.
> > + *
> > + * FIXME: This function should be noinstr but the below local_irq_save() is
> > + * unsafe because it involves illegal RCU uses through tracing and lockdep.
> > + * This must be fixed first.
> >   */
> >  void rcu_idle_exit(void)
> >  {
> 
> Urgh, except this one... I'm sure I fixed that at some point. Clearly
> that never made it in :/

I found my patches and brushed them off, see here:

  https://lkml.kernel.org/r/20220519212750.656413111@infradead.org