rcu: Per-CPU operation cleanups to rcu_*_qs() functions

The rcu_bh_qs(), rcu_preempt_qs(), and rcu_sched_qs() functions use
old-style per-CPU variable access and write to ->passed_quiesce even
if it is already set.  This commit therefore updates to use the new-style
per-CPU variable access functions and avoids the spurious writes.
This commit also eliminates the "cpu" argument to these functions because
they are always invoked on the indicated CPU.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 18 insertions, 16 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c880f5387b1f..4c340625ffd4 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -188,22 +188,24 @@ static int rcu_gp_in_progress(struct rcu_state *rsp)
  * one since the start of the grace period, this just sets a flag.
  * The caller must have disabled preemption.
  */
-void rcu_sched_qs(int cpu)
+void rcu_sched_qs(void)
 {
-        struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
-
-        if (rdp->passed_quiesce == 0)
-                trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs"));
-        rdp->passed_quiesce = 1;
+        if (!__this_cpu_read(rcu_sched_data.passed_quiesce)) {
+                trace_rcu_grace_period(TPS("rcu_sched"),
+                                       __this_cpu_read(rcu_sched_data.gpnum),
+                                       TPS("cpuqs"));
+                __this_cpu_write(rcu_sched_data.passed_quiesce, 1);
+        }
 }
 
-void rcu_bh_qs(int cpu)
+void rcu_bh_qs(void)
 {
-        struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
-
-        if (rdp->passed_quiesce == 0)
-                trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs"));
-        rdp->passed_quiesce = 1;
+        if (!__this_cpu_read(rcu_bh_data.passed_quiesce)) {
+                trace_rcu_grace_period(TPS("rcu_bh"),
+                                       __this_cpu_read(rcu_bh_data.gpnum),
+                                       TPS("cpuqs"));
+                __this_cpu_write(rcu_bh_data.passed_quiesce, 1);
+        }
 }
 
 static DEFINE_PER_CPU(int, rcu_sched_qs_mask);
@@ -278,7 +280,7 @@ static void rcu_momentary_dyntick_idle(void)
 void rcu_note_context_switch(int cpu)
 {
         trace_rcu_utilization(TPS("Start context switch"));
-        rcu_sched_qs(cpu);
+        rcu_sched_qs();
         rcu_preempt_note_context_switch(cpu);
         if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
                 rcu_momentary_dyntick_idle();
@@ -2395,8 +2397,8 @@ void rcu_check_callbacks(int cpu, int user)
                  * at least not while the corresponding CPU is online.
                  */
 
-                rcu_sched_qs(cpu);
-                rcu_bh_qs(cpu);
+                rcu_sched_qs();
+                rcu_bh_qs();
 
         } else if (!in_softirq()) {
 
@@ -2407,7 +2409,7 @@ void rcu_check_callbacks(int cpu, int user)
                  * critical section, so note it.
                  */
 
-                rcu_bh_qs(cpu);
+                rcu_bh_qs();
         }
         rcu_preempt_check_callbacks(cpu);
         if (rcu_pending(cpu))