FAILED: patch "[PATCH] hwmon: chipcap2: synchronize ready IRQ state" failed to apply to 6.12-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 8c02722be2caa6604a837b81faeaba78250eda4a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109200721-failed-6.12-8c02722be2ca@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 8c02722be2caa6604a837b81faeaba78250eda4a Mon Sep 17 00:00:00 2001
From: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Date: Wed, 14 Oct 2026 19:34:10 +0200
Subject: [PATCH] hwmon: chipcap2: synchronize ready IRQ state

The ready IRQ handler can race with reinit_completion() in the enable
path. In particular, a handler from an earlier operation can complete
the completion after it is reset for a new operation.

Use irq_lock to serialize access to the completion and process_irqs.
Disable IRQ processing and synchronize any running handler before resetting
the completion for a new operation.

Fixes: 3af350929e75 ("hwmon: Add support for Amphenol ChipCap 2")
Cc: stable@vger.kernel.org
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20261014-chipcap2_locks-v3-11-27ebfc2c5b9e@gmail.com
[groeck: Dropped obsolete 'Assisted-by: tag]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/chipcap2.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/chipcap2.c b/drivers/hwmon/chipcap2.c
index b3b725cc7224f..00f62a33d4637 100644
--- a/drivers/hwmon/chipcap2.c
+++ b/drivers/hwmon/chipcap2.c
@@ -123,6 +123,16 @@ static int cc2_enable(struct cc2_data *data)
 {
 	int ret;
 
+	if (data->irq_ready > 0) {
+		scoped_guard(mutex, &data->irq_lock)
+			data->process_irqs = false;
+
+		synchronize_irq(data->irq_ready);
+
+		scoped_guard(mutex, &data->irq_lock)
+			reinit_completion(&data->complete);
+	}
+
 	/* exclusive regulator, check in case a disable failed */
 	if (data->regulator_enabled) {
 		scoped_guard(mutex, &data->irq_lock)
@@ -130,9 +140,6 @@ static int cc2_enable(struct cc2_data *data)
 		return 0;
 	}
 
-	/* clear any pending completion */
-	try_wait_for_completion(&data->complete);
-
 	ret = regulator_enable(data->regulator);
 	if (ret < 0)
 		return ret;
@@ -162,6 +169,9 @@ static void cc2_disable(struct cc2_data *data)
 	scoped_guard(mutex, &data->irq_lock)
 		data->process_irqs = false;
 
+	if (data->irq_ready > 0)
+		synchronize_irq(data->irq_ready);
+
 	/* exclusive regulator, check in case an enable failed */
 	if (!data->regulator_enabled)
 		return;
@@ -510,8 +520,10 @@ static irqreturn_t cc2_ready_interrupt(int irq, void *data)
 {
 	struct cc2_data *cc2 = data;
 
-	if (cc2->process_irqs)
-		complete(&cc2->complete);
+	scoped_guard(mutex, &cc2->irq_lock) {
+		if (cc2->process_irqs)
+			complete(&cc2->complete);
+	}
 
 	return IRQ_HANDLED;
 }
-- 
2.53.0