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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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2013-11-17 21:08:07 -08:00
parent ffa83fb565
commit f1f399d128
1 changed files with 5 additions and 2 deletions
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7
kernel/rcu/tree_plugin.h
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@ -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 */
}
/*