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rcu: Refactor rcu_barrier() empty-list handling

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This commit saves a few lines by checking first for an empty callback
list.  If the callback list is empty, then that CPU is taken care of,
regardless of its online or nocb state.  Also simplify tracing accordingly
and fold a few lines together.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney
2021-12-10 16:25:20 -08:00
parent 82980b1622
commit 0cabb47af3
2 changed files with 12 additions and 22 deletions
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25
kernel/rcu/tree.c
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@@ -4030,8 +4030,7 @@ void rcu_barrier(void)
/* Did someone else do our work for us? */
if (rcu_seq_done(&rcu_state.barrier_sequence, s)) {
rcu_barrier_trace(TPS("EarlyExit"), -1,
rcu_state.barrier_sequence);
rcu_barrier_trace(TPS("EarlyExit"), -1, rcu_state.barrier_sequence);
smp_mb(); /* caller's subsequent code after above check. */
mutex_unlock(&rcu_state.barrier_mutex);
return;
@@ -4059,26 +4058,18 @@ void rcu_barrier(void)
*/
for_each_possible_cpu(cpu) {
rdp = per_cpu_ptr(&rcu_data, cpu);
if (cpu_is_offline(cpu) &&
!rcu_rdp_is_offloaded(rdp))
if (!rcu_segcblist_n_cbs(&rdp->cblist)) {
rcu_barrier_trace(TPS("NQ"), cpu, rcu_state.barrier_sequence);
continue;
if (rcu_segcblist_n_cbs(&rdp->cblist) && cpu_online(cpu)) {
rcu_barrier_trace(TPS("OnlineQ"), cpu,
rcu_state.barrier_sequence);
}
if (cpu_online(cpu)) {
rcu_barrier_trace(TPS("OnlineQ"), cpu, rcu_state.barrier_sequence);
smp_call_function_single(cpu, rcu_barrier_func, (void *)cpu, 1);
} else if (rcu_segcblist_n_cbs(&rdp->cblist) &&
cpu_is_offline(cpu)) {
rcu_barrier_trace(TPS("OfflineNoCBQ"), cpu,
rcu_state.barrier_sequence);
} else {
rcu_barrier_trace(TPS("OfflineNoCBQ"), cpu, rcu_state.barrier_sequence);
local_irq_disable();
rcu_barrier_func((void *)cpu);
local_irq_enable();
} else if (cpu_is_offline(cpu)) {
rcu_barrier_trace(TPS("OfflineNoCBNoQ"), cpu,
rcu_state.barrier_sequence);
} else {
rcu_barrier_trace(TPS("OnlineNQ"), cpu,
rcu_state.barrier_sequence);
}
}
cpus_read_unlock();