linux-kernel - [PATCH] Input: gpio-keys - fix a sleep while atomic with PREEMPT

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Message-ID: <20250526-gpio_keys_preempt_rt-v1-1-09ddadf8e19d@foss.st.com>
Date: Mon, 26 May 2025 15:56:29 +0200
From: Gatien Chevallier <gatien.chevallier@...s.st.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Sebastian Andrzej Siewior
	<bigeasy@...utronix.de>,
        Clark Williams <clrkwllms@...nel.org>,
        Steven
 Rostedt <rostedt@...dmis.org>,
        Paul Cercueil <paul@...pouillou.net>
CC: <linux-input@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-rt-devel@...ts.linux.dev>,
        Fabrice Gasnier
	<fabrice.gasnier@...s.st.com>,
        Gatien Chevallier
	<gatien.chevallier@...s.st.com>
Subject: [PATCH] Input: gpio-keys - fix a sleep while atomic with
 PREEMPT_RT

From: Fabrice Gasnier <fabrice.gasnier@...s.st.com>

When enabling PREEMPT_RT, the gpio_keys_irq_timer() callback runs in
hard irq context, but the input_event() takes a spin_lock, which isn't
allowed there as it is converted to a rt_spin_lock().

[ 4054.289999] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
[ 4054.290028] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/0
...
[ 4054.290195]  __might_resched+0x13c/0x1f4
[ 4054.290209]  rt_spin_lock+0x54/0x11c
[ 4054.290219]  input_event+0x48/0x80
[ 4054.290230]  gpio_keys_irq_timer+0x4c/0x78
[ 4054.290243]  __hrtimer_run_queues+0x1a4/0x438
[ 4054.290257]  hrtimer_interrupt+0xe4/0x240
[ 4054.290269]  arch_timer_handler_phys+0x2c/0x44
[ 4054.290283]  handle_percpu_devid_irq+0x8c/0x14c
[ 4054.290297]  handle_irq_desc+0x40/0x58
[ 4054.290307]  generic_handle_domain_irq+0x1c/0x28
[ 4054.290316]  gic_handle_irq+0x44/0xcc

Considering the gpio_keys_irq_isr() can run in any context, e.g. it can
be threaded, it seems there's no point in requesting the timer isr to
run in hard irq context.

So relax the hrtimer not to use the hard context. This requires the
spin_lock to be added back in gpio_keys_irq_timer().

Fixes: 019002f20cb5 ("Input: gpio-keys - use hrtimer for release timer")
Suggested-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...s.st.com>
Signed-off-by: Gatien Chevallier <gatien.chevallier@...s.st.com>
---
 drivers/input/keyboard/gpio_keys.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c
index 5c39a217b94c8ad03a8542380eed741fccdca5da..99fc7d3c29ea5809604915782525fecacb151612 100644
--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c
@@ -448,12 +448,15 @@ static enum hrtimer_restart gpio_keys_irq_timer(struct hrtimer *t)
 						      struct gpio_button_data,
 						      release_timer);
 	struct input_dev *input = bdata->input;
+	unsigned long flags;
 
+	spin_lock_irqsave(&bdata->lock, flags);
 	if (bdata->key_pressed) {
 		input_report_key(input, *bdata->code, 0);
 		input_sync(input);
 		bdata->key_pressed = false;
 	}
+	spin_unlock_irqrestore(&bdata->lock, flags);
 
 	return HRTIMER_NORESTART;
 }
@@ -486,7 +489,7 @@ static irqreturn_t gpio_keys_irq_isr(int irq, void *dev_id)
 	if (bdata->release_delay)
 		hrtimer_start(&bdata->release_timer,
 			      ms_to_ktime(bdata->release_delay),
-			      HRTIMER_MODE_REL_HARD);
+			      HRTIMER_MODE_REL);
 out:
 	return IRQ_HANDLED;
 }
@@ -628,7 +631,7 @@ static int gpio_keys_setup_key(struct platform_device *pdev,
 
 		bdata->release_delay = button->debounce_interval;
 		hrtimer_setup(&bdata->release_timer, gpio_keys_irq_timer,
-			      CLOCK_REALTIME, HRTIMER_MODE_REL_HARD);
+			      CLOCK_REALTIME, HRTIMER_MODE_REL);
 
 		isr = gpio_keys_irq_isr;
 		irqflags = 0;

---
base-commit: 0ff41df1cb268fc69e703a08a57ee14ae967d0ca
change-id: 20250526-gpio_keys_preempt_rt-10619c8fa916

Best regards,
-- 
Gatien Chevallier <gatien.chevallier@...s.st.com>