releases/4.19.34/net-dsa-mv88e6xxx-add-lockdep-classes-to-fix-false-p.patch

   1 From 8c71f4771d4741642ee2aab0681d0d277823f0d4 Mon Sep 17 00:00:00 2001
   2 From: Andrew Lunn <andrew@lunn.ch>
   3 Date: Sat, 23 Feb 2019 17:43:56 +0100
   4 Subject: net: dsa: mv88e6xxx: Add lockdep classes to fix false positive splat
   5
   6 [ Upstream commit f6d9758b12660484b6639364cc406da92a918c96 ]
   7
   8 The following false positive lockdep splat has been observed.
   9
  10 ======================================================
  11 WARNING: possible circular locking dependency detected
  12 4.20.0+ #302 Not tainted
  13 ------------------------------------------------------
  14 systemd-udevd/160 is trying to acquire lock:
  15 edea6080 (&chip->reg_lock){+.+.}, at: __setup_irq+0x640/0x704
  16
  17 but task is already holding lock:
  18 edff0340 (&desc->request_mutex){+.+.}, at: __setup_irq+0xa0/0x704
  19
  20 which lock already depends on the new lock.
  21
  22 the existing dependency chain (in reverse order) is:
  23
  24 -> #1 (&desc->request_mutex){+.+.}:
  25        mutex_lock_nested+0x1c/0x24
  26        __setup_irq+0xa0/0x704
  27        request_threaded_irq+0xd0/0x150
  28        mv88e6xxx_probe+0x41c/0x694 [mv88e6xxx]
  29        mdio_probe+0x2c/0x54
  30        really_probe+0x200/0x2c4
  31        driver_probe_device+0x5c/0x174
  32        __driver_attach+0xd8/0xdc
  33        bus_for_each_dev+0x58/0x7c
  34        bus_add_driver+0xe4/0x1f0
  35        driver_register+0x7c/0x110
  36        mdio_driver_register+0x24/0x58
  37        do_one_initcall+0x74/0x2e8
  38        do_init_module+0x60/0x1d0
  39        load_module+0x1968/0x1ff4
  40        sys_finit_module+0x8c/0x98
  41        ret_fast_syscall+0x0/0x28
  42        0xbedf2ae8
  43
  44 -> #0 (&chip->reg_lock){+.+.}:
  45        __mutex_lock+0x50/0x8b8
  46        mutex_lock_nested+0x1c/0x24
  47        __setup_irq+0x640/0x704
  48        request_threaded_irq+0xd0/0x150
  49        mv88e6xxx_g2_irq_setup+0xcc/0x1b4 [mv88e6xxx]
  50        mv88e6xxx_probe+0x44c/0x694 [mv88e6xxx]
  51        mdio_probe+0x2c/0x54
  52        really_probe+0x200/0x2c4
  53        driver_probe_device+0x5c/0x174
  54        __driver_attach+0xd8/0xdc
  55        bus_for_each_dev+0x58/0x7c
  56        bus_add_driver+0xe4/0x1f0
  57        driver_register+0x7c/0x110
  58        mdio_driver_register+0x24/0x58
  59        do_one_initcall+0x74/0x2e8
  60        do_init_module+0x60/0x1d0
  61        load_module+0x1968/0x1ff4
  62        sys_finit_module+0x8c/0x98
  63        ret_fast_syscall+0x0/0x28
  64        0xbedf2ae8
  65
  66 other info that might help us debug this:
  67
  68  Possible unsafe locking scenario:
  69
  70        CPU0                    CPU1
  71        ----                    ----
  72   lock(&desc->request_mutex);
  73                                lock(&chip->reg_lock);
  74                                lock(&desc->request_mutex);
  75   lock(&chip->reg_lock);
  76
  77 &desc->request_mutex refer to two different mutex. #1 is the GPIO for
  78 the chip interrupt. #2 is the chained interrupt between global 1 and
  79 global 2.
  80
  81 Add lockdep classes to the GPIO interrupt to avoid this.
  82
  83 Reported-by: Russell King <rmk+kernel@armlinux.org.uk>
  84 Signed-off-by: Andrew Lunn <andrew@lunn.ch>
  85 Signed-off-by: David S. Miller <davem@davemloft.net>
  86
  87 Signed-off-by: Sasha Levin <sashal@kernel.org>
  88 ---
  89  drivers/net/dsa/mv88e6xxx/chip.c | 8 ++++++++
  90  1 file changed, 8 insertions(+)
  91
  92 diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
  93 index c078c791f481..dabe89968a78 100644
  94 --- a/drivers/net/dsa/mv88e6xxx/chip.c
  95 +++ b/drivers/net/dsa/mv88e6xxx/chip.c
  96 @@ -442,12 +442,20 @@ out_mapping:
  97
  98  static int mv88e6xxx_g1_irq_setup(struct mv88e6xxx_chip *chip)
  99  {
 100 +       static struct lock_class_key lock_key;
 101 +       static struct lock_class_key request_key;
 102         int err;
 103
 104         err = mv88e6xxx_g1_irq_setup_common(chip);
 105         if (err)
 106                 return err;
 107
 108 +       /* These lock classes tells lockdep that global 1 irqs are in
 109 +        * a different category than their parent GPIO, so it won't
 110 +        * report false recursion.
 111 +        */
 112 +       irq_set_lockdep_class(chip->irq, &lock_key, &request_key);
 113 +
 114         err = request_threaded_irq(chip->irq, NULL,
 115                                    mv88e6xxx_g1_irq_thread_fn,
 116                                    IRQF_ONESHOT,
 117 --
 118 2.19.1
 119