drivers/base/regmap/internal.h | 1 + drivers/base/regmap/regcache-maple.c | 3 +++ drivers/base/regmap/regmap.c | 1 + 3 files changed, 5 insertions(+)
In some cases when using the maple tree register cache, the lockdep
validator might complain about invalid deadlocks:
[7.131886] Possible interrupt unsafe locking scenario:
[7.131890] CPU0 CPU1
[7.131893] ---- ----
[7.131896] lock(&mt->ma_lock);
[7.131904] local_irq_disable();
[7.131907] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
[7.131916] lock(&mt->ma_lock);
[7.131925] <Interrupt>
[7.131928] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
[7.131936]
*** DEADLOCK ***
[7.131939] no locks held by swapper/0/0.
[7.131944]
the shortest dependencies between 2nd lock and 1st lock:
[7.131950] -> (&mt->ma_lock){+.+.}-{2:2} {
[7.131966] HARDIRQ-ON-W at:
[7.131973] lock_acquire+0x200/0x330
[7.131986] _raw_spin_lock+0x50/0x70
[7.131998] regcache_maple_write+0x68/0xe0
[7.132010] regcache_write+0x6c/0x90
[7.132019] _regmap_read+0x19c/0x1d0
[7.132029] _regmap_update_bits+0xc0/0x148
[7.132038] regmap_update_bits_base+0x6c/0xa8
[7.132048] rk8xx_probe+0x22c/0x3d8
[7.132057] rk8xx_spi_probe+0x74/0x88
[7.132065] spi_probe+0xa8/0xe0
[...]
[7.132675] }
[7.132678] ... key at: [<ffff800082943c20>] __key.0+0x0/0x10
[7.132691] ... acquired at:
[7.132695] _raw_spin_lock+0x50/0x70
[7.132704] regcache_maple_write+0x68/0xe0
[7.132714] regcache_write+0x6c/0x90
[7.132724] _regmap_read+0x19c/0x1d0
[7.132732] _regmap_update_bits+0xc0/0x148
[7.132741] regmap_field_update_bits_base+0x74/0xb8
[7.132751] vop2_plane_atomic_update+0x480/0x14d8 [rockchipdrm]
[7.132820] drm_atomic_helper_commit_planes+0x1a0/0x320 [drm_kms_helper]
[...]
[7.135112] -> (rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock){-...}-{2:2} {
[7.135130] IN-HARDIRQ-W at:
[7.135136] lock_acquire+0x200/0x330
[7.135147] _raw_spin_lock_irqsave+0x6c/0x98
[7.135157] regmap_lock_spinlock+0x20/0x40
[7.135166] regmap_read+0x44/0x90
[7.135175] vop2_isr+0x90/0x290 [rockchipdrm]
[7.135225] __handle_irq_event_percpu+0x124/0x2d0
In the example above, the validator seems to get the scope of
dependencies wrong, since the regmap instance used in rk8xx-spi driver
has nothing to do with the instance from vop2.
Improve validation by sharing the regmap's lockdep class with the maple
tree's internal lock, while also providing a subclass for the latter.
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
Changes in v2:
- Rebased onto next-20241031 to fix the conflicts reported by Mark
- Link to v1: https://lore.kernel.org/r/20241029-regmap-maple-lockdep-fix-v1-1-7589e57390bd@collabora.com
---
drivers/base/regmap/internal.h | 1 +
drivers/base/regmap/regcache-maple.c | 3 +++
drivers/base/regmap/regmap.c | 1 +
3 files changed, 5 insertions(+)
diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 83acccdc1008976de681396a300b78b701bbfa3c..bdb450436cbc53031c3d921f9f6067d26eca2549 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -59,6 +59,7 @@ struct regmap {
unsigned long raw_spinlock_flags;
};
};
+ struct lock_class_key *lock_key;
regmap_lock lock;
regmap_unlock unlock;
void *lock_arg; /* This is passed to lock/unlock functions */
diff --git a/drivers/base/regmap/regcache-maple.c b/drivers/base/regmap/regcache-maple.c
index 8d27d3653ea3e71e7b134cd3e47be385860e7375..23da7b31d7153450e1b16528be47216d7fbdd872 100644
--- a/drivers/base/regmap/regcache-maple.c
+++ b/drivers/base/regmap/regcache-maple.c
@@ -355,6 +355,9 @@ static int regcache_maple_init(struct regmap *map)
mt_init(mt);
+ if (!mt_external_lock(mt) && map->lock_key)
+ lockdep_set_class_and_subclass(&mt->ma_lock, map->lock_key, 1);
+
if (!map->num_reg_defaults)
return 0;
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 4ded93687c1f0ab3584947c61398cd6333b2e72c..53131a7ede0a6aad54bc85e970124f6b166a8010 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -745,6 +745,7 @@ struct regmap *__regmap_init(struct device *dev,
lock_key, lock_name);
}
map->lock_arg = map;
+ map->lock_key = lock_key;
}
/*
---
base-commit: f9f24ca362a4d84dd8aeb4b8f3ec28cb6c43dd06
change-id: 20241029-regmap-maple-lockdep-fix-f368ce6e7363On Thu, 31 Oct 2024 18:37:04 +0200, Cristian Ciocaltea wrote:
> In some cases when using the maple tree register cache, the lockdep
> validator might complain about invalid deadlocks:
>
> [7.131886] Possible interrupt unsafe locking scenario:
>
> [7.131890] CPU0 CPU1
> [7.131893] ---- ----
> [7.131896] lock(&mt->ma_lock);
> [7.131904] local_irq_disable();
> [7.131907] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
> [7.131916] lock(&mt->ma_lock);
> [7.131925] <Interrupt>
> [7.131928] lock(rockchip_drm_vop2:3114:(&vop2_regmap_config)->lock);
> [7.131936]
> *** DEADLOCK ***
>
> [...]
Applied to
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git for-next
Thanks!
[1/1] regmap: maple: Provide lockdep (sub)class for maple tree's internal lock
commit: 1ed9b927e7dd8b8cff13052efe212a8ff72ec51d
All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.
You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.
If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.
Please add any relevant lists and maintainers to the CCs when replying
to this mail.
Thanks,
Mark
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