linux-kernel - [PATCH 3/6] workqueue: Don't assume that the callback has interrupts disabled

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Date:   Thu, 13 Jun 2019 16:50:24 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 3/6] workqueue: Don't assume that the callback has interrupts disabled

Due to the TIMER_IRQSAFE flag, the timer callback is invoked with
disabled interrupts. On -RT the callback is invoked in softirq context
with enabled interrupts. Since the interrupts are threaded, there are
are no in_irq() users. The local_bh_disable() around the threaded
handler ensures that there is either a timer or a threaded handler
active on the CPU.

Disable interrupts before __queue_work() is invoked from the timer
callback.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/workqueue.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 601d61150b65d..a3c2959e5c4f0 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1611,9 +1611,11 @@ EXPORT_SYMBOL_GPL(queue_work_node);
 void delayed_work_timer_fn(struct timer_list *t)
 {
 	struct delayed_work *dwork = from_timer(dwork, t, timer);
+	unsigned long flags;
 
-	/* should have been called from irqsafe timer with irq already off */
+	local_irq_save(flags);
 	__queue_work(dwork->cpu, dwork->wq, &dwork->work);
+	local_irq_restore(flags);
 }
 EXPORT_SYMBOL(delayed_work_timer_fn);
 
-- 
2.20.1