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rcu: Define rcu_all_qs() only in !PREEMPT builds

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Now that rcu_all_qs() is used only in !PREEMPT builds, move it to
tree_plugin.h so that it is defined only in those builds.  This in
turn means that rcu_momentary_dyntick_idle() is only used in !PREEMPT
builds, but it is simply marked __maybe_unused in order to keep it
near the rest of the dyntick-idle code.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2018-07-10 14:00:14 -07:00
parent 4d232dfe1d
commit 395a2f097e
3 changed files with 42 additions and 40 deletions
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39
kernel/rcu/tree_plugin.h
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@@ -947,6 +947,45 @@ static void rcu_qs(void)
rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
}
/*
* Register an urgently needed quiescent state. If there is an
* emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight
* dyntick-idle quiescent state visible to other CPUs, which will in
* some cases serve for expedited as well as normal grace periods.
* Either way, register a lightweight quiescent state.
*
* The barrier() calls are redundant in the common case when this is
* called externally, but just in case this is called from within this
* file.
*
*/
void rcu_all_qs(void)
{
unsigned long flags;
if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs))
return;
preempt_disable();
/* Load rcu_urgent_qs before other flags. */
if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) {
preempt_enable();
return;
}
this_cpu_write(rcu_dynticks.rcu_urgent_qs, false);
barrier(); /* Avoid RCU read-side critical sections leaking down. */
if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) {
local_irq_save(flags);
rcu_momentary_dyntick_idle();
local_irq_restore(flags);
}
if (unlikely(raw_cpu_read(rcu_data.cpu_no_qs.b.exp)))
rcu_qs();
this_cpu_inc(rcu_dynticks.rcu_qs_ctr);
barrier(); /* Avoid RCU read-side critical sections leaking up. */
preempt_enable();
}
EXPORT_SYMBOL_GPL(rcu_all_qs);
/*
* Note a PREEMPT=n context switch. The caller must have disabled interrupts.
*/