linux-kernel - Re: [PATCH 1/2] rcu: declare rcu_eqs_special

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Date:   Sun, 25 Mar 2018 22:18:27 +0300
From:   Yury Norov <ynorov@...iumnetworks.com>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Chris Metcalf <cmetcalf@...lanox.com>,
        Christopher Lameter <cl@...ux.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Mark Rutland <mark.rutland@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-ppc@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] rcu: declare rcu_eqs_special_set() in public header

On Sun, Mar 25, 2018 at 12:12:43PM -0700, Paul E. McKenney wrote:
> On Sun, Mar 25, 2018 at 08:50:03PM +0300, Yury Norov wrote:
> > rcu_eqs_special_set() is declared only in internal header
> > kernel/rcu/tree.h and stubbed in include/linux/rcutiny.h.
> > 
> > This patch declares rcu_eqs_special_set() in include/linux/rcutree.h, so
> > it can be used in non-rcu kernel code.
> > 
> > Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
> > ---
> >  include/linux/rcutree.h | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
> > index fd996cdf1833..448f20f27396 100644
> > --- a/include/linux/rcutree.h
> > +++ b/include/linux/rcutree.h
> > @@ -74,6 +74,7 @@ static inline void synchronize_rcu_bh_expedited(void)
> >  void rcu_barrier(void);
> >  void rcu_barrier_bh(void);
> >  void rcu_barrier_sched(void);
> > +bool rcu_eqs_special_set(int cpu);
> >  unsigned long get_state_synchronize_rcu(void);
> >  void cond_synchronize_rcu(unsigned long oldstate);
> >  unsigned long get_state_synchronize_sched(void);
> 
> Good point, a bit hard to use otherwise.  ;-)
> 
> I removed the declaration from rcutree.h and updated the commit log as
> follows.  Does it look OK?
 
Of course.

Thanks,
Yury
 
> ------------------------------------------------------------------------
> 
> commit 4497105b718a819072d48a675916d9d200b5327f
> Author: Yury Norov <ynorov@...iumnetworks.com>
> Date:   Sun Mar 25 20:50:03 2018 +0300
> 
>     rcu: Declare rcu_eqs_special_set() in public header
>     
>     Because rcu_eqs_special_set() is declared only in internal header
>     kernel/rcu/tree.h and stubbed in include/linux/rcutiny.h, it is
>     inaccessible outside of the RCU implementation.  This patch therefore
>     moves the  rcu_eqs_special_set() declaration to include/linux/rcutree.h,
>     which allows it to be used in non-rcu kernel code.
>     
>     Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
>     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
> index fd996cdf1833..448f20f27396 100644
> --- a/include/linux/rcutree.h
> +++ b/include/linux/rcutree.h
> @@ -74,6 +74,7 @@ static inline void synchronize_rcu_bh_expedited(void)
>  void rcu_barrier(void);
>  void rcu_barrier_bh(void);
>  void rcu_barrier_sched(void);
> +bool rcu_eqs_special_set(int cpu);
>  unsigned long get_state_synchronize_rcu(void);
>  void cond_synchronize_rcu(unsigned long oldstate);
>  unsigned long get_state_synchronize_sched(void);
> diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
> index 59ad0e23c722..d5f617aaa744 100644
> --- a/kernel/rcu/tree.h
> +++ b/kernel/rcu/tree.h
> @@ -415,7 +415,6 @@ extern struct rcu_state rcu_preempt_state;
>  #endif /* #ifdef CONFIG_PREEMPT_RCU */
>  
>  int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
> -bool rcu_eqs_special_set(int cpu);
>  
>  #ifdef CONFIG_RCU_BOOST
>  DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);