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SubjectRe: [PATCH RFC tip/core/rcu 1/2] Eliminate redundant rcu_sysidle_state variable
On Wed, Jul 23, 2014 at 09:28:52AM -0700, Paul E. McKenney wrote:
> 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>

Acked-by: Frederic Weisbecker <fweisbec@gmail.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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