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Subject[PATCH RFC tip/core/rcu 1/2] Eliminate redundant rcu_sysidle_state variable
Now that we have rcu_state_p, which references rcu_preempt_state for
TREE_PREEMPT_RCU and rcu_sched_state for TREE_RCU, we don't need a
separate rcu_sysidle_state variable. This commit therefore eliminates
rcu_preempt_state in favor of rcu_state_p.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 24f5bd54ca9b..e31fa71c4d3a 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2662,16 +2662,6 @@ static void __maybe_unused rcu_kick_nohz_cpu(int cpu)

#ifdef CONFIG_NO_HZ_FULL_SYSIDLE

-/*
- * Define RCU flavor that holds sysidle state. This needs to be the
- * most active flavor of RCU.
- */
-#ifdef CONFIG_PREEMPT_RCU
-static struct rcu_state *rcu_sysidle_state = &rcu_preempt_state;
-#else /* #ifdef CONFIG_PREEMPT_RCU */
-static struct rcu_state *rcu_sysidle_state = &rcu_sched_state;
-#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
-
static int full_sysidle_state; /* Current system-idle state. */
#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */
#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */
@@ -2813,7 +2803,7 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
* not the flavor of RCU that tracks sysidle state, or if this
* is an offline or the timekeeping CPU, nothing to do.
*/
- if (!*isidle || rdp->rsp != rcu_sysidle_state ||
+ if (!*isidle || rdp->rsp != rcu_state_p ||
cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu)
return;
if (rcu_gp_in_progress(rdp->rsp))
@@ -2839,7 +2829,7 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
*/
static bool is_sysidle_rcu_state(struct rcu_state *rsp)
{
- return rsp == rcu_sysidle_state;
+ return rsp == rcu_state_p;
}

/*
@@ -2917,7 +2907,7 @@ static void rcu_sysidle_cancel(void)
static void rcu_sysidle_report(struct rcu_state *rsp, int isidle,
unsigned long maxj, bool gpkt)
{
- if (rsp != rcu_sysidle_state)
+ if (rsp != rcu_state_p)
return; /* Wrong flavor, ignore. */
if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL)
return; /* Running state machine from timekeeping CPU. */
@@ -2986,13 +2976,12 @@ bool rcu_sys_is_idle(void)

/* Scan all the CPUs looking for nonidle CPUs. */
for_each_possible_cpu(cpu) {
- rdp = per_cpu_ptr(rcu_sysidle_state->rda, cpu);
+ rdp = per_cpu_ptr(rcu_state_p->rda, cpu);
rcu_sysidle_check_cpu(rdp, &isidle, &maxj);
if (!isidle)
break;
}
- rcu_sysidle_report(rcu_sysidle_state,
- isidle, maxj, false);
+ rcu_sysidle_report(rcu_state_p, isidle, maxj, false);
oldrss = rss;
rss = ACCESS_ONCE(full_sysidle_state);
}
@@ -3019,7 +3008,7 @@ bool rcu_sys_is_idle(void)
* provided by the memory allocator.
*/
if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL &&
- !rcu_gp_in_progress(rcu_sysidle_state) &&
+ !rcu_gp_in_progress(rcu_state_p) &&
!rsh.inuse && xchg(&rsh.inuse, 1) == 0)
call_rcu(&rsh.rh, rcu_sysidle_cb);
return false;


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