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Commit f1f399d1 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Optimize RCU_FAST_NO_HZ for RCU_NOCB_CPU_ALL 



If CONFIG_RCU_NOCB_CPU_ALL=y, then no CPU will ever have RCU callbacks
because these callbacks will instead be handled by the rcuo kthreads.
However, the current version of RCU_FAST_NO_HZ nevertheless checks for RCU
callbacks.  This commit therefore creates static inline implementations
of rcu_prepare_for_idle() and rcu_cleanup_after_idle() that are no-ops
when CONFIG_RCU_NOCB_CPU_ALL=y.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent ffa83fb5

kernel/rcu/tree_plugin.h

+5 −2
Original line number Diff line number Diff line
@@ -1658,7 +1658,7 @@ extern int tick_nohz_active; 
 * only if it has been awhile since the last time we did so.  Afterwards,

 * if there are any callbacks ready for immediate invocation, return true.

 */

static bool rcu_try_advance_all_cbs(void)

static bool __maybe_unused rcu_try_advance_all_cbs(void)

{

	bool cbs_ready = false;

	struct rcu_data *rdp;
@@ -1743,6 +1743,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj) 
 */

static void rcu_prepare_for_idle(int cpu)

{

#ifndef CONFIG_RCU_NOCB_CPU_ALL

	struct rcu_data *rdp;

	struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);

	struct rcu_node *rnp;
@@ -1794,6 +1795,7 @@ static void rcu_prepare_for_idle(int cpu) 
		rcu_accelerate_cbs(rsp, rnp, rdp);

		raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */

	}

#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */

}



/*
@@ -1803,11 +1805,12 @@ static void rcu_prepare_for_idle(int cpu) 
 */

static void rcu_cleanup_after_idle(int cpu)

{



#ifndef CONFIG_RCU_NOCB_CPU_ALL

	if (rcu_is_nocb_cpu(cpu))

		return;

	if (rcu_try_advance_all_cbs())

		invoke_rcu_core();

#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */

}



/*