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Subject[PATCH 5.15 197/262] pinctrl: sunxi: Use unique lockdep classes for IRQs
Date
From: Samuel Holland <samuel@sholland.org>

commit bac129dbc6560dfeb634c03f0c08b78024e71915 upstream.

This driver, like several others, uses a chained IRQ for each GPIO bank,
and forwards .irq_set_wake to the GPIO bank's upstream IRQ. As a result,
a call to irq_set_irq_wake() needs to lock both the upstream and
downstream irq_desc's. Lockdep considers this to be a possible deadlock
when the irq_desc's share lockdep classes, which they do by default:

============================================
WARNING: possible recursive locking detected
5.17.0-rc3-00394-gc849047c2473 #1 Not tainted
--------------------------------------------
init/307 is trying to acquire lock:
c2dfe27c (&irq_desc_lock_class){-.-.}-{2:2}, at: __irq_get_desc_lock+0x58/0xa0

but task is already holding lock:
c3c0ac7c (&irq_desc_lock_class){-.-.}-{2:2}, at: __irq_get_desc_lock+0x58/0xa0

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 init/307:
#0: c1f29f18 (system_transition_mutex){+.+.}-{3:3}, at: __do_sys_reboot+0x90/0x23c
#1: c20f7760 (&dev->mutex){....}-{3:3}, at: device_shutdown+0xf4/0x224
#2: c2e804d8 (&dev->mutex){....}-{3:3}, at: device_shutdown+0x104/0x224
#3: c3c0ac7c (&irq_desc_lock_class){-.-.}-{2:2}, at: __irq_get_desc_lock+0x58/0xa0

stack backtrace:
CPU: 0 PID: 307 Comm: init Not tainted 5.17.0-rc3-00394-gc849047c2473 #1
Hardware name: Allwinner sun8i Family
unwind_backtrace from show_stack+0x10/0x14
show_stack from dump_stack_lvl+0x68/0x90
dump_stack_lvl from __lock_acquire+0x1680/0x31a0
__lock_acquire from lock_acquire+0x148/0x3dc
lock_acquire from _raw_spin_lock_irqsave+0x50/0x6c
_raw_spin_lock_irqsave from __irq_get_desc_lock+0x58/0xa0
__irq_get_desc_lock from irq_set_irq_wake+0x2c/0x19c
irq_set_irq_wake from irq_set_irq_wake+0x13c/0x19c
[tail call from sunxi_pinctrl_irq_set_wake]
irq_set_irq_wake from gpio_keys_suspend+0x80/0x1a4
gpio_keys_suspend from gpio_keys_shutdown+0x10/0x2c
gpio_keys_shutdown from device_shutdown+0x180/0x224
device_shutdown from __do_sys_reboot+0x134/0x23c
__do_sys_reboot from ret_fast_syscall+0x0/0x1c

However, this can never deadlock because the upstream and downstream
IRQs are never the same (nor do they even involve the same irqchip).

Silence this erroneous lockdep splat by applying what appears to be the
usual fix of moving the GPIO IRQs to separate lockdep classes.

Fixes: a59c99d9eaf9 ("pinctrl: sunxi: Forward calls to irq_set_irq_wake")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20220216040037.22730-1-samuel@sholland.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/pinctrl/sunxi/pinctrl-sunxi.c | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/drivers/pinctrl/sunxi/pinctrl-sunxi.c
+++ b/drivers/pinctrl/sunxi/pinctrl-sunxi.c
@@ -36,6 +36,13 @@
#include "../core.h"
#include "pinctrl-sunxi.h"

+/*
+ * These lock classes tell lockdep that GPIO IRQs are in a different
+ * category than their parents, so it won't report false recursion.
+ */
+static struct lock_class_key sunxi_pinctrl_irq_lock_class;
+static struct lock_class_key sunxi_pinctrl_irq_request_class;
+
static struct irq_chip sunxi_pinctrl_edge_irq_chip;
static struct irq_chip sunxi_pinctrl_level_irq_chip;

@@ -1551,6 +1558,8 @@ int sunxi_pinctrl_init_with_variant(stru
for (i = 0; i < (pctl->desc->irq_banks * IRQ_PER_BANK); i++) {
int irqno = irq_create_mapping(pctl->domain, i);

+ irq_set_lockdep_class(irqno, &sunxi_pinctrl_irq_lock_class,
+ &sunxi_pinctrl_irq_request_class);
irq_set_chip_and_handler(irqno, &sunxi_pinctrl_edge_irq_chip,
handle_edge_irq);
irq_set_chip_data(irqno, pctl);

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