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Message-Id: <20241031-regmap-maple-lockdep-fix-v2-1-06a3710f3623@collabora.com>
Date: Thu, 31 Oct 2024 18:37:04 +0200
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Mark Brown <broonie@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>
Cc: Heiko Stuebner <heiko@...ech.de>, Andy Yan <andy.yan@...k-chips.com>,
kernel@...labora.com, linux-kernel@...r.kernel.org
Subject: [PATCH RFC v2] regmap: maple: Provide lockdep (sub)class for maple
tree's internal lock
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@...labora.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-f368ce6e7363
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