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From: Frederic Weisbecker <frederic@kernel.org>
To: "Paul E . McKenney" <paulmck@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Neeraj Upadhyay <neeraju@codeaurora.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Josh Triplett <josh@joshtriplett.org>,
	rcu@vger.kernel.org
Subject: [PATCH 13/19] rcu/nocb: Locally accelerate callbacks as long as offloading isn't complete
Date: Fri, 13 Nov 2020 13:13:28 +0100	[thread overview]
Message-ID: <20201113121334.166723-14-frederic@kernel.org> (raw)
In-Reply-To: <20201113121334.166723-1-frederic@kernel.org>

The local callbacks processing checks if some callbacks need
acceleration. Keep that behaviour under nocb lock protection when
rcu_core() executes concurrently with GP/CB kthreads.

Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
---
 kernel/rcu/tree.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index cc141337f3f9..b24d60a52f34 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2690,7 +2690,6 @@ static __latent_entropy void rcu_core(void)
 	unsigned long flags;
 	struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
 	struct rcu_node *rnp = rdp->mynode;
-	const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
 	const bool do_batch = !rcu_segcblist_completely_offloaded(&rdp->cblist);
 
 	if (cpu_is_offline(smp_processor_id()))
@@ -2711,11 +2710,11 @@ static __latent_entropy void rcu_core(void)
 
 	/* No grace period and unregistered callbacks? */
 	if (!rcu_gp_in_progress() &&
-	    rcu_segcblist_is_enabled(&rdp->cblist) && !offloaded) {
-		local_irq_save(flags);
+	    rcu_segcblist_is_enabled(&rdp->cblist) && do_batch) {
+		rcu_nocb_lock_irqsave(rdp, flags);
 		if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
 			rcu_accelerate_cbs_unlocked(rnp, rdp);
-		local_irq_restore(flags);
+		rcu_nocb_unlock_irqrestore(rdp, flags);
 	}
 
 	rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check());
-- 
2.25.1


  parent reply	other threads:[~2020-11-13 12:14 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-13 12:13 [PATCH 00/19] rcu/nocb: De-offload and re-offload support v4 Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 01/19] rcu/nocb: Turn enabled/offload states into a common flag Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 02/19] rcu/nocb: Provide basic callback offloading state machine bits Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 03/19] rcu/nocb: Always init segcblist on CPU up Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 04/19] rcu/nocb: De-offloading CB kthread Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 05/19] rcu/nocb: Don't deoffload an offline CPU with pending work Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 06/19] rcu/nocb: De-offloading GP kthread Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 07/19] rcu/nocb: Re-offload support Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 08/19] rcu/nocb: Shutdown nocb timer on de-offloading Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 09/19] rcu: Flush bypass before setting SEGCBLIST_SOFTIRQ_ONLY Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 10/19] rcu/nocb: Set SEGCBLIST_SOFTIRQ_ONLY at the very last stage of de-offloading Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 11/19] rcu/nocb: Only cond_resched() from actual offloaded batch processing Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 12/19] rcu/nocb: Process batch locally as long as offloading isn't complete Frederic Weisbecker
2020-11-13 12:13 ` Frederic Weisbecker [this message]
2020-11-13 12:13 ` [PATCH 14/19] tools/rcutorture: Support nocb toggle in TREE01 Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 15/19] rcutorture: Remove weak nocb declarations Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 16/19] rcutorture: Export nocb (de)offloading functions Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 17/19] cpu/hotplug: Add lockdep_is_cpus_held() Frederic Weisbecker
2020-12-15 23:49   ` Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 18/19] timer: Add timer_curr_running() Frederic Weisbecker
2020-11-13 12:13 ` [PATCH 19/19] rcu/nocb: Detect unsafe checks for offloaded rdp Frederic Weisbecker
2020-12-08  2:41 ` [PATCH 00/19] rcu/nocb: De-offload and re-offload support v4 Boqun Feng
2020-12-08 12:51   ` Frederic Weisbecker
2020-12-10  1:21     ` Paul E. McKenney
2020-12-10  3:08       ` Boqun Feng
2020-12-16 16:59 ` Paul E. McKenney
2020-12-29 14:21   ` Frederic Weisbecker

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