target/linux/ipq806x/patches/0026-pinctrl-msm-Silence-recursive-lockdep-warning.patch

   1 From 9588c91936434166007c3a15ad7f4e2f3729c5e7 Mon Sep 17 00:00:00 2001
   2 From: Stephen Boyd <sboyd@codeaurora.org>
   3 Date: Thu, 6 Mar 2014 22:44:40 -0800
   4 Subject: [PATCH 026/182] pinctrl: msm: Silence recursive lockdep warning
   5
   6 If a driver calls enable_irq_wake() on a gpio turned interrupt
   7 from the msm pinctrl driver we'll get a lockdep warning like so:
   8
   9 =============================================
  10 [ INFO: possible recursive locking detected ]
  11 3.14.0-rc3 #2 Not tainted
  12 ---------------------------------------------
  13 modprobe/52 is trying to acquire lock:
  14  (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88
  15
  16 but task is already holding lock:
  17  (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88
  18
  19 other info that might help us debug this:
  20  Possible unsafe locking scenario:
  21
  22        CPU0
  23        ----
  24   lock(&irq_desc_lock_class);
  25   lock(&irq_desc_lock_class);
  26
  27  *** DEADLOCK ***
  28
  29  May be due to missing lock nesting notation
  30
  31 4 locks held by modprobe/52:
  32  #0:  (&__lockdep_no_validate__){......}, at: [<c04f2864>] __driver_attach+0x48/0x98
  33  #1:  (&__lockdep_no_validate__){......}, at: [<c04f2874>] __driver_attach+0x58/0x98
  34  #2:  (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88
  35  #3:  (&(&pctrl->lock)->rlock){......}, at: [<c04bb4b8>] msm_gpio_irq_set_wake+0x20/0xa8
  36
  37 Silence it by putting the gpios into their own lock class.
  38
  39 Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
  40 Acked-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
  41 Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
  42 ---
  43  drivers/pinctrl/pinctrl-msm.c |    7 +++++++
  44  1 file changed, 7 insertions(+)
  45
  46 diff --git a/drivers/pinctrl/pinctrl-msm.c b/drivers/pinctrl/pinctrl-msm.c
  47 index 0e43fdd..e61b30a 100644
  48 --- a/drivers/pinctrl/pinctrl-msm.c
  49 +++ b/drivers/pinctrl/pinctrl-msm.c
  50 @@ -857,6 +857,12 @@ static void msm_gpio_irq_handler(unsigned int irq, struct irq_desc *desc)
  51         chained_irq_exit(chip, desc);
  52  }
  53
  54 +/*
  55 + * This lock class tells lockdep that GPIO irqs are in a different
  56 + * category than their parents, so it won't report false recursion.
  57 + */
  58 +static struct lock_class_key gpio_lock_class;
  59 +
  60  static int msm_gpio_init(struct msm_pinctrl *pctrl)
  61  {
  62         struct gpio_chip *chip;
  63 @@ -895,6 +901,7 @@ static int msm_gpio_init(struct msm_pinctrl *pctrl)
  64
  65         for (i = 0; i < chip->ngpio; i++) {
  66                 irq = irq_create_mapping(pctrl->domain, i);
  67 +               irq_set_lockdep_class(irq, &gpio_lock_class);
  68                 irq_set_chip_and_handler(irq, &msm_gpio_irq_chip, handle_edge_irq);
  69                 irq_set_chip_data(irq, pctrl);
  70         }
  71 --
  72 1.7.10.4
  73