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

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Message-Id: <20180325191243.GH3675@linux.vnet.ibm.com>
Date:   Sun, 25 Mar 2018 12:12:43 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Yury Norov <ynorov@...iumnetworks.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 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?

							Thanx, Paul

------------------------------------------------------------------------

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);