linux-kernel - [tip: core/rcu] rcu/nocb: Only cond_resched() from actual offloaded batch processing

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Message-ID: <161313343834.23325.16043726274859719159.tip-bot2@tip-bot2>
Date:   Fri, 12 Feb 2021 12:37:18 -0000
From:   "tip-bot2 for Frederic Weisbecker" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Boqun Feng <boqun.feng@...il.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: core/rcu] rcu/nocb: Only cond_resched() from actual offloaded
 batch processing

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     e3abe959fbd57aa751bc533677a35c411cee9b16
Gitweb:        https://git.kernel.org/tip/e3abe959fbd57aa751bc533677a35c411cee9b16
Author:        Frederic Weisbecker <frederic@...nel.org>
AuthorDate:    Fri, 13 Nov 2020 13:13:26 +01:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Wed, 06 Jan 2021 16:24:59 -08:00

rcu/nocb: Only cond_resched() from actual offloaded batch processing

During a toggle operations, rcu_do_batch() may be invoked concurrently
by softirqs and offloaded processing for a given CPU's callbacks.
This commit therefore makes sure cond_resched() is invoked only from
the offloaded context.

Cc: Josh Triplett <josh@...htriplett.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Lai Jiangshan <jiangshanlai@...il.com>
Cc: Joel Fernandes <joel@...lfernandes.org>
Cc: Neeraj Upadhyay <neeraju@...eaurora.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Inspired-by: Paul E. McKenney <paulmck@...nel.org>
Tested-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/tree.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 83362f6..4ef59a5 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2516,8 +2516,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
 			/* Exceeded the time limit, so leave. */
 			break;
 		}
-		if (offloaded) {
-			WARN_ON_ONCE(in_serving_softirq());
+		if (!in_serving_softirq()) {
 			local_bh_enable();
 			lockdep_assert_irqs_enabled();
 			cond_resched_tasks_rcu_qs();