[PATCH RFC] regmap: maple: Switch to use irq-safe locking
Cristian Ciocaltea
cristian.ciocaltea at collabora.com
Tue Aug 13 15:20:21 PDT 2024
Commit 3d59c22bbb8d ("drm/rockchip: vop2: Convert to use maple tree
register cache") enabled the use of maple tree register cache in
Rockchip VOP2 driver. However, building the kernel with lockdep support
indicates locking rules violation when trying to unload the rockchipdrm
module:
[ 48.360258] ========================================================
[ 48.360829] WARNING: possible irq lock inversion dependency detected
[ 48.361400] 6.11.0-rc1 #40 Not tainted
[ 48.361743] --------------------------------------------------------
[ 48.362311] modprobe/685 just changed the state of lock:
[ 48.362790] ffff0000087fa798 (&mt->ma_lock){+...}-{2:2}, at: regcache_maple_exit+0x6c/0xe0
[ 48.363554] but this lock was taken by another, HARDIRQ-safe lock in the past:
[ 48.364212] (rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock){-.-.}-{2:2}
[ 48.364226]
and interrupts could create inverse lock ordering between them.
[ 48.365874]
other info that might help us debug this:
[ 48.366460] Possible interrupt unsafe locking scenario:
[ 48.367069] CPU0 CPU1
[ 48.367478] ---- ----
[ 48.367889] lock(&mt->ma_lock);
[ 48.368197] local_irq_disable();
[ 48.368729] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
[ 48.369551] lock(&mt->ma_lock);
[ 48.370081] <Interrupt>
[ 48.370336] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
[ 48.370957]
*** DEADLOCK ***
[ 48.371489] 2 locks held by modprobe/685:
[ 48.371854] #0: ffff0000018898f8 (&dev->mutex){....}-{3:3}, at: device_release_driver_internal+0x54/0x210
[ 48.372739] #1: ffff800081c6ca80 (component_mutex){+.+.}-{3:3}, at: component_del+0x38/0x158
[ 48.373522]
the shortest dependencies between 2nd lock and 1st lock:
[ 48.374235] -> (rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock){-.-.}-{2:2} {
[ 48.374941] IN-HARDIRQ-W at:
[ 48.375239] lock_acquire+0x1d4/0x320
[ 48.375739] _raw_spin_lock_irqsave+0x6c/0x98
[ 48.376300] regmap_lock_spinlock+0x20/0x40
[ 48.376845] regmap_read+0x44/0x88
[ 48.377321] vop2_isr+0x90/0x290 [rockchipdrm]
[ 48.377919] __handle_irq_event_percpu+0x114/0x2b0
[ 48.378519] handle_irq_event+0x54/0xb8
[ 48.379032] handle_fasteoi_irq+0x158/0x228
[ 48.379577] generic_handle_domain_irq+0x34/0x58
[ 48.380160] gic_handle_irq+0xa4/0x114
[...]
[ 48.466666] -> (&mt->ma_lock){+...}-{2:2} {
[ 48.467066] HARDIRQ-ON-W at:
[ 48.467360] lock_acquire+0x1d4/0x320
[ 48.467849] _raw_spin_lock+0x50/0x70
[ 48.468337] regcache_maple_exit+0x6c/0xe0
[ 48.468864] regcache_exit+0x8c/0xa8
[ 48.469344] regmap_exit+0x24/0x160
[ 48.469815] devm_regmap_release+0x1c/0x28
[ 48.470339] release_nodes+0x68/0xa8
[ 48.470818] devres_release_group+0x120/0x180
[ 48.471364] component_unbind+0x54/0x70
[ 48.471867] component_unbind_all+0xb0/0xe8
[ 48.472400] rockchip_drm_unbind+0x44/0x80 [rockchipdrm]
[ 48.473059] component_del+0xc8/0x158
[ 48.473545] dw_hdmi_rockchip_remove+0x28/0x40 [rockchipdrm]
The problem is that the regmap lock could be taken by an IRQ context,
interrupting the irq-unsafe maple tree lock, which may result in a lock
inversion deadlock scenario.
Switch to use irq-safe locking in the maple tree register cache.
Fixes: f033c26de5a5 ("regmap: Add maple tree based register cache")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea at collabora.com>
---
drivers/base/regmap/regcache-maple.c | 29 ++++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/drivers/base/regmap/regcache-maple.c b/drivers/base/regmap/regcache-maple.c
index 2dea9d259c49..7b2433c9747e 100644
--- a/drivers/base/regmap/regcache-maple.c
+++ b/drivers/base/regmap/regcache-maple.c
@@ -13,6 +13,9 @@
#include "internal.h"
+#define mas_lock_irq(mas, flags) spin_lock_irqsave(&((mas)->tree->ma_lock), flags)
+#define mas_unlock_irq(mas, flags) spin_unlock_irqrestore(&((mas)->tree->ma_lock), flags)
+
static int regcache_maple_read(struct regmap *map,
unsigned int reg, unsigned int *value)
{
@@ -42,6 +45,7 @@ static int regcache_maple_write(struct regmap *map, unsigned int reg,
MA_STATE(mas, mt, reg, reg);
unsigned long *entry, *upper, *lower;
unsigned long index, last;
+ unsigned long flags;
size_t lower_sz, upper_sz;
int ret;
@@ -89,18 +93,18 @@ static int regcache_maple_write(struct regmap *map, unsigned int reg,
* is redundant, but we need to take it due to lockdep asserts
* in the maple tree code.
*/
- mas_lock(&mas);
+ mas_lock_irq(&mas, flags);
mas_set_range(&mas, index, last);
ret = mas_store_gfp(&mas, entry, map->alloc_flags);
- mas_unlock(&mas);
+ mas_unlock_irq(&mas, flags);
if (ret == 0) {
kfree(lower);
kfree(upper);
}
-
+
return ret;
}
@@ -113,12 +117,13 @@ static int regcache_maple_drop(struct regmap *map, unsigned int min,
/* initialized to work around false-positive -Wuninitialized warning */
unsigned long lower_index = 0, lower_last = 0;
unsigned long upper_index, upper_last;
+ unsigned long flags;
int ret = 0;
lower = NULL;
upper = NULL;
- mas_lock(&mas);
+ mas_lock_irq(&mas, flags);
mas_for_each(&mas, entry, max) {
/*
@@ -126,7 +131,7 @@ static int regcache_maple_drop(struct regmap *map, unsigned int min,
* Maple lock is redundant, but we need to take it due
* to lockdep asserts in the maple tree code.
*/
- mas_unlock(&mas);
+ mas_unlock_irq(&mas, flags);
/* Do we need to save any of this entry? */
if (mas.index < min) {
@@ -156,7 +161,7 @@ static int regcache_maple_drop(struct regmap *map, unsigned int min,
}
kfree(entry);
- mas_lock(&mas);
+ mas_lock_irq(&mas, flags);
mas_erase(&mas);
/* Insert new nodes with the saved data */
@@ -178,7 +183,7 @@ static int regcache_maple_drop(struct regmap *map, unsigned int min,
}
out:
- mas_unlock(&mas);
+ mas_unlock_irq(&mas, flags);
out_unlocked:
kfree(lower);
kfree(upper);
@@ -295,16 +300,17 @@ static int regcache_maple_exit(struct regmap *map)
struct maple_tree *mt = map->cache;
MA_STATE(mas, mt, 0, UINT_MAX);
unsigned int *entry;
+ unsigned long flags;
/* if we've already been called then just return */
if (!mt)
return 0;
- mas_lock(&mas);
+ mas_lock_irq(&mas, flags);
mas_for_each(&mas, entry, UINT_MAX)
kfree(entry);
__mt_destroy(mt);
- mas_unlock(&mas);
+ mas_unlock_irq(&mas, flags);
kfree(mt);
map->cache = NULL;
@@ -318,6 +324,7 @@ static int regcache_maple_insert_block(struct regmap *map, int first,
struct maple_tree *mt = map->cache;
MA_STATE(mas, mt, first, last);
unsigned long *entry;
+ unsigned long flags;
int i, ret;
entry = kcalloc(last - first + 1, sizeof(unsigned long), map->alloc_flags);
@@ -327,13 +334,13 @@ static int regcache_maple_insert_block(struct regmap *map, int first,
for (i = 0; i < last - first + 1; i++)
entry[i] = map->reg_defaults[first + i].def;
- mas_lock(&mas);
+ mas_lock_irq(&mas, flags);
mas_set_range(&mas, map->reg_defaults[first].reg,
map->reg_defaults[last].reg);
ret = mas_store_gfp(&mas, entry, map->alloc_flags);
- mas_unlock(&mas);
+ mas_unlock_irq(&mas, flags);
if (ret)
kfree(entry);
---
base-commit: 9e6869691724b12e1f43655eeedc35fade38120c
change-id: 20240814-regcache-maple-irq-safe-1e93ffa4e146
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