[PATCH 6.6 008/283] rcu: Remove local_irq_save/restore() in rcu_preempt_deferred_qs_handler()

Sasha Levin
2026-02-28T18:07:17Z

From: Zqiang <qiang.zhang@linux.dev>

[ Upstream commit 42d590d100f2e47e47d974a902b9ed610e464824 ]

The per-CPU rcu_data structure's ->defer_qs_iw field is initialized
by IRQ_WORK_INIT_HARD(), which means that the subsequent invocation of
rcu_preempt_deferred_qs_handler() will always be executed with interrupts
disabled. This commit therefore removes the local_irq_save/restore()
operations from rcu_preempt_deferred_qs_handler() and adds a call to
lockdep_assert_irqs_disabled() in order to enable lockdep to diagnose
mistaken invocations of this function from interrupts-enabled code.

Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Stable-dep-of: d41e37f26b31 ("rcu: Fix rcu_read_unlock() deadloop due to softirq")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/rcu/tree_plugin.h | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 18a8fd116fdff..04044b492cc31 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -615,11 +615,10 @@ notrace void rcu_preempt_deferred_qs(struct task_struct *t)
*/
static void rcu_preempt_deferred_qs_handler(struct irq_work *iwp)
{
- unsigned long flags;
struct rcu_data *rdp;

+ lockdep_assert_irqs_disabled();
rdp = container_of(iwp, struct rcu_data, defer_qs_iw);
- local_irq_save(flags);

/*
* If the IRQ work handler happens to run in the middle of RCU read-side
@@ -636,8 +635,6 @@ static void rcu_preempt_deferred_qs_handler(struct irq_work *iwp)
*/
if (rcu_preempt_depth() > 0)
WRITE_ONCE(rdp->defer_qs_iw_pending, DEFER_QS_IDLE);
-
- local_irq_restore(flags);
}

/*
--
2.51.0