[PATCH 10/11] rcu: clear the special.b.need_qs in rcu_note_context_switch()

Lai Jiangshan
2019-10-31T10:09:01Z

It is better to clear the special.b.need_qs when it is
replaced by special.b.blocked or it is really fulfill its
goal in rcu_preempt_deferred_qs_irqrestore().

It makes rcu_qs() easier to be understood, and also prepares for
the percpu rcu_preempt_depth patch, which reqires rcu_special
bits to be clearred in irq-disable context.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
kernel/rcu/tree_plugin.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 81cacf637865..21bb04fec0d2 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -264,8 +264,6 @@ static void rcu_qs(void)
__this_cpu_read(rcu_data.gp_seq),
TPS("cpuqs"));
__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
- barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */
- WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false);
}
}

@@ -297,6 +295,7 @@ void rcu_note_context_switch(bool preempt)
/* Possibly blocking in an RCU read-side critical section. */
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp);
+ t->rcu_read_unlock_special.b.need_qs = false;
t->rcu_read_unlock_special.b.blocked = true;
t->rcu_blocked_node = rnp;

--
2.20.1