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

[tip-bot2 for Frederic Weisbecker]

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@xxxxxxxxxx>
AuthorDate:    Fri, 13 Nov 2020 13:13:26 +01:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Inspired-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Tested-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 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();