linux-kernel - [PATCH 1/7] pinctrl: msm: Silence recursive lockdep warning

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Message-Id: <1394174686-8358-2-git-send-email-sboyd@codeaurora.org>
Date:	Thu,  6 Mar 2014 22:44:40 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>
Subject: [PATCH 1/7] pinctrl: msm: Silence recursive lockdep warning

If a driver calls enable_irq_wake() on a gpio turned interrupt
from the msm pinctrl driver we'll get a lockdep warning like so:

=============================================
[ INFO: possible recursive locking detected ]
3.14.0-rc3 #2 Not tainted
---------------------------------------------
modprobe/52 is trying to acquire lock:
 (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88

but task is already holding lock:
 (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&irq_desc_lock_class);
  lock(&irq_desc_lock_class);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by modprobe/52:
 #0:  (&__lockdep_no_validate__){......}, at: [<c04f2864>] __driver_attach+0x48/0x98
 #1:  (&__lockdep_no_validate__){......}, at: [<c04f2874>] __driver_attach+0x58/0x98
 #2:  (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88
 #3:  (&(&pctrl->lock)->rlock){......}, at: [<c04bb4b8>] msm_gpio_irq_set_wake+0x20/0xa8

Silence it by putting the gpios into their own lock class.

Cc: Bjorn Andersson <bjorn.andersson@...ymobile.com>
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
 drivers/pinctrl/pinctrl-msm.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pinctrl/pinctrl-msm.c b/drivers/pinctrl/pinctrl-msm.c
index ef2bf3126da6..ac7223dab4a3 100644
--- a/drivers/pinctrl/pinctrl-msm.c
+++ b/drivers/pinctrl/pinctrl-msm.c
@@ -869,6 +869,12 @@ static void msm_gpio_irq_handler(unsigned int irq, struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
+/*
+ * This lock class tells lockdep that GPIO irqs are in a different
+ * category than their parents, so it won't report false recursion.
+ */
+static struct lock_class_key gpio_lock_class;
+
 static int msm_gpio_init(struct msm_pinctrl *pctrl)
 {
 	struct gpio_chip *chip;
@@ -907,6 +913,7 @@ static int msm_gpio_init(struct msm_pinctrl *pctrl)
 
 	for (i = 0; i < chip->ngpio; i++) {
 		irq = irq_create_mapping(pctrl->domain, i);
+		irq_set_lockdep_class(irq, &gpio_lock_class);
 		irq_set_chip_and_handler(irq, &msm_gpio_irq_chip, handle_edge_irq);
 		irq_set_chip_data(irq, pctrl);
 	}
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

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