linux-kernel - [PATCH tip/core/rcu 19/19] rcu: Remove rcu_data_p pointer to default rcu

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Message-Id: <20180829222047.319-19-paulmck@linux.vnet.ibm.com>
Date:   Wed, 29 Aug 2018 15:20:47 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 19/19] rcu: Remove rcu_data_p pointer to default rcu_data structure

The rcu_data_p pointer references the default set of per-CPU rcu_data
structures, that is, those that call_rcu() uses, as opposed to
call_rcu_bh() and sometimes call_rcu_sched().  But there is now only one
set of per-CPU rcu_data structures, so that one set is by definition
the default, which means that the rcu_data_p pointer no longer serves
any useful purpose.  This commit therefore removes it.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c        |  1 -
 kernel/rcu/tree_plugin.h | 10 +++++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a3bcf08ad596..f0e7e3972fd9 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -85,7 +85,6 @@ struct rcu_state rcu_state = {
 	.ofl_lock = __SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),
 };
 
-static struct rcu_data __percpu *const rcu_data_p = &rcu_data;
 LIST_HEAD(rcu_struct_flavors);
 
 /* Dump rcu_node combining tree at boot to verify correct setup. */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 329d5802d899..18175ca19f34 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -302,11 +302,11 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
 static void rcu_qs(void)
 {
 	RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!\n");
-	if (__this_cpu_read(rcu_data_p->cpu_no_qs.s)) {
+	if (__this_cpu_read(rcu_data.cpu_no_qs.s)) {
 		trace_rcu_grace_period(TPS("rcu_preempt"),
-				       __this_cpu_read(rcu_data_p->gp_seq),
+				       __this_cpu_read(rcu_data.gp_seq),
 				       TPS("cpuqs"));
-		__this_cpu_write(rcu_data_p->cpu_no_qs.b.norm, false);
+		__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
 		barrier(); /* Coordinate with rcu_flavor_check_callbacks(). */
 		current->rcu_read_unlock_special.b.need_qs = false;
 	}
@@ -805,8 +805,8 @@ static void rcu_flavor_check_callbacks(int user)
 
 	/* If GP is oldish, ask for help from rcu_read_unlock_special(). */
 	if (t->rcu_read_lock_nesting > 0 &&
-	    __this_cpu_read(rcu_data_p->core_needs_qs) &&
-	    __this_cpu_read(rcu_data_p->cpu_no_qs.b.norm) &&
+	    __this_cpu_read(rcu_data.core_needs_qs) &&
+	    __this_cpu_read(rcu_data.cpu_no_qs.b.norm) &&
 	    !t->rcu_read_unlock_special.b.need_qs &&
 	    time_after(jiffies, rsp->gp_start + HZ))
 		t->rcu_read_unlock_special.b.need_qs = true;
-- 
2.17.1