From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
Lai Jiangshan <laijs@linux.alibaba.com>,
"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 08/11] rcu: Clear ->rcu_read_unlock_special only once
Date: Mon, 9 Dec 2019 20:26:26 -0800 [thread overview]
Message-ID: <20191210042629.3808-8-paulmck@kernel.org> (raw)
In-Reply-To: <20191210042606.GA3624@paulmck-ThinkPad-P72>
From: Lai Jiangshan <laijs@linux.alibaba.com>
In rcu_preempt_deferred_qs_irqrestore(), ->rcu_read_unlock_special is
cleared one piece at a time. Given that the "if" statements in this
function use the copy in "special", this commit removes the clearing
of the individual pieces in favor of clearing ->rcu_read_unlock_special
in one go just after it has been determined to be non-zero.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tree_plugin.h | 19 +++----------------
1 file changed, 3 insertions(+), 16 deletions(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 7487c79..c3a3271 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -444,16 +444,9 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
local_irq_restore(flags);
return;
}
- t->rcu_read_unlock_special.b.exp_hint = false;
- t->rcu_read_unlock_special.b.deferred_qs = false;
- if (special.b.need_qs) {
+ t->rcu_read_unlock_special.s = 0;
+ if (special.b.need_qs)
rcu_qs();
- t->rcu_read_unlock_special.b.need_qs = false;
- if (!t->rcu_read_unlock_special.s && !rdp->exp_deferred_qs) {
- local_irq_restore(flags);
- return;
- }
- }
/*
* Respond to a request by an expedited grace period for a
@@ -461,17 +454,11 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
* tasks are handled when removing the task from the
* blocked-tasks list below.
*/
- if (rdp->exp_deferred_qs) {
+ if (rdp->exp_deferred_qs)
rcu_report_exp_rdp(rdp);
- if (!t->rcu_read_unlock_special.s) {
- local_irq_restore(flags);
- return;
- }
- }
/* Clean up if blocked during RCU read-side critical section. */
if (special.b.blocked) {
- t->rcu_read_unlock_special.b.blocked = false;
/*
* Remove this task from the list it blocked on. The task
--
2.9.5
next prev parent reply other threads:[~2019-12-10 4:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-10 4:26 [PATCH tip/core/rcu 0/11] Preemptible-RCU updates for v5.6 Paul E. McKenney
2019-12-10 4:26 ` [PATCH tip/core/rcu 01/11] rcu/nocb: Fix dump_tree hierarchy print always active paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 02/11] rcu: Avoid data-race in rcu_gp_fqs_check_wake() paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 03/11] rcu: Use lockdep rather than comment to enforce lock held paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 04/11] rcu: Make PREEMPT_RCU be a modifier to TREE_RCU paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 05/11] rcu: Use CONFIG_PREEMPTION where appropriate paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 06/11] rcu: Rename some instance of CONFIG_PREEMPTION to CONFIG_PREEMPT_RCU paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 07/11] rcu: Clear .exp_hint only when deferred quiescent state has been reported paulmck
2019-12-10 4:26 ` paulmck [this message]
2019-12-10 4:26 ` [PATCH tip/core/rcu 09/11] rcu: Use READ_ONCE() for ->expmask in rcu_read_unlock_special() paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 10/11] rcu: Provide wrappers for uses of ->rcu_read_lock_nesting paulmck
2019-12-10 4:26 ` [PATCH tip/core/rcu 11/11] rcu: Avoid tick_dep_set_cpu() misordering paulmck
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