linux-kernel - Re: [PATCH] rcu: add declarations of undeclared items

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Date:   Fri, 11 Oct 2019 21:44:30 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:     linux-kernel@...ts.codethink.co.uk,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: add declarations of undeclared items

On Fri, Oct 11, 2019 at 06:08:24PM +0100, Ben Dooks wrote:
> The rcu_state, rcu_rnp_online_cpus and rcu_dynticks_curr_cpu_in_eqs
> do not have declarations in a header. Add these to remove the
> following sparse warnings:
> 
> kernel/rcu/tree.c:87:18: warning: symbol 'rcu_state' was not declared. Should it be static?
> kernel/rcu/tree.c:191:15: warning: symbol 'rcu_rnp_online_cpus' was not declared. Should it be static?
> kernel/rcu/tree.c:297:6: warning: symbol 'rcu_dynticks_curr_cpu_in_eqs' was not declared. Should it be static?
> 
> Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>

Good catch!

However, these guys (plus one more) are actually used only in the
kernel/rcu/tree.o translation unit, so they can be marked static.
I made this change as shown below with your Reported-by.

Seem reasonable?

							Thanx, Paul

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

commit 02995691aa76f3e52599d4f9d9d1ab23c3574f32
Author: Paul E. McKenney <paulmck@...nel.org>
Date:   Fri Oct 11 21:40:09 2019 -0700

    rcu: Mark non-global functions and variables as static
    
    Each of rcu_state, rcu_rnp_online_cpus(), rcu_dynticks_curr_cpu_in_eqs(),
    and rcu_dynticks_snap() are used only in the kernel/rcu/tree.o translation
    unit, and may thus be marked static.  This commit therefore makes this
    change.
    
    Reported-by: Ben Dooks <ben.dooks@...ethink.co.uk>
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b18fa3d..278798e 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -85,7 +85,7 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
 	.dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
 	.dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR),
 };
-struct rcu_state rcu_state = {
+static struct rcu_state rcu_state = {
 	.level = { &rcu_state.node[0] },
 	.gp_state = RCU_GP_IDLE,
 	.gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT,
@@ -189,7 +189,7 @@ EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio);
  * held, but the bit corresponding to the current CPU will be stable
  * in most contexts.
  */
-unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
+static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
 {
 	return READ_ONCE(rnp->qsmaskinitnext);
 }
@@ -295,7 +295,7 @@ static void rcu_dynticks_eqs_online(void)
  *
  * No ordering, as we are sampling CPU-local information.
  */
-bool rcu_dynticks_curr_cpu_in_eqs(void)
+static bool rcu_dynticks_curr_cpu_in_eqs(void)
 {
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
@@ -306,7 +306,7 @@ bool rcu_dynticks_curr_cpu_in_eqs(void)
  * Snapshot the ->dynticks counter with full ordering so as to allow
  * stable comparison of this counter with past and future snapshots.
  */
-int rcu_dynticks_snap(struct rcu_data *rdp)
+static int rcu_dynticks_snap(struct rcu_data *rdp)
 {
 	int snap = atomic_add_return(0, &rdp->dynticks);
 
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 1540542..f8e6c70 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -402,8 +402,6 @@ static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
 #define RCU_NAME rcu_name
 #endif /* #else #ifdef CONFIG_TRACING */
 
-int rcu_dynticks_snap(struct rcu_data *rdp);
-
 /* Forward declarations for tree_plugin.h */
 static void rcu_bootup_announce(void);
 static void rcu_qs(void);