[PATCH] drm: fb-helper: Avoid nesting spinlock_t into raw_spinlock_t
From: Jiri Kosina
Date: Tue Feb 15 2022 - 10:46:39 EST
From: Jiri Kosina <jkosina@xxxxxxx>
drm_fb_helper_damage() is acquiring spinlock_t (helper->damage_lock),
while it can be called from contexts where raw_spinlock_t is held (e.g.
console_owner lock obtained on vprintk_emit() codepath).
As the critical sections protected by damage_lock are super-tiny, let's
fix this by converting it to raw_spinlock_t in order not to violate
PREEMPT_RT-imposed lock nesting rules.
This fixes the splat below.
=============================
[ BUG: Invalid wait context ]
5.17.0-rc4-00002-gd567f5db412e #1 Not tainted
-----------------------------
swapper/0/0 is trying to lock:
ffff8c5687cc4158 (&helper->damage_lock){....}-{3:3}, at: drm_fb_helper_damage.isra.22+0x4a/0xf0
other info that might help us debug this:
context-{2:2}
3 locks held by swapper/0/0:
#0: ffffffffad776520 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0xb8/0x2a0
#1: ffffffffad696120 (console_owner){-...}-{0:0}, at: console_unlock+0x17f/0x550
#2: ffffffffad926a58 (printing_lock){....}-{3:3}, at: vt_console_print+0x7d/0x3e0
stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.17.0-rc4-00002-gd567f5db412e #1 bed1d5e19e0e7e8c9d97fd8afa1322f7f47a4f38
Hardware name: LENOVO 20UJS2B905/20UJS2B905, BIOS R1CET63W(1.32 ) 04/09/2021
Call Trace:
<IRQ>
dump_stack_lvl+0x58/0x71
__lock_acquire+0x165b/0x1780
? secondary_startup_64_no_verify+0xd5/0xdb
lock_acquire+0x278/0x300
? drm_fb_helper_damage.isra.22+0x4a/0xf0
? save_trace+0x3e/0x340
? __bfs+0x10f/0x240
_raw_spin_lock_irqsave+0x48/0x60
? drm_fb_helper_damage.isra.22+0x4a/0xf0
drm_fb_helper_damage.isra.22+0x4a/0xf0
soft_cursor+0x194/0x240
bit_cursor+0x386/0x630
? get_color+0x29/0x120
? bit_putcs+0x4b0/0x4b0
? console_unlock+0x17f/0x550
hide_cursor+0x2f/0x90
vt_console_print+0x3c5/0x3e0
? console_unlock+0x17f/0x550
console_unlock+0x515/0x550
vprintk_emit+0x1c8/0x2a0
_printk+0x52/0x6e
? sched_clock_tick+0x3d/0x60
collect_cpu_info_amd+0x93/0xd0
collect_cpu_info_local+0x23/0x30
flush_smp_call_function_queue+0x137/0x220
__sysvec_call_function_single+0x43/0x1c0
sysvec_call_function_single+0x43/0x80
</IRQ>
<TASK>
asm_sysvec_call_function_single+0x12/0x20
RIP: 0010:cpuidle_enter_state+0x111/0x4b0
Code: 7c ff 45 84 ff 74 17 9c 58 0f 1f 44 00 00 f6 c4 02 0f 85 71 03 00 00 31 ff e8 bb 21 86 ff e8 76 2f 8e ff fb 66 0f 1f 44 00 00 <45> 85 f6 0f 88 12 01 00 00 49 63 d6 4c 2b 24 24 48 8d 04 52 48 8d
RSP: 0018:ffffffffad603e48 EFLAGS: 00000206
RAX: 00000000000127c3 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffac32617a
RBP: ffff8c5687ba4400 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffffad603e10 R11: 0000000000000000 R12: 00000000685eb4a0
R13: ffffffffad918f80 R14: 0000000000000003 R15: 0000000000000000
? cpuidle_enter_state+0x10a/0x4b0
? cpuidle_enter_state+0x10a/0x4b0
cpuidle_enter+0x29/0x40
do_idle+0x24d/0x2c0
cpu_startup_entry+0x19/0x20
start_kernel+0x9c2/0x9e9
secondary_startup_64_no_verify+0xd5/0xdb
</TASK>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
---
drivers/gpu/drm/drm_fb_helper.c | 14 +++++++-------
include/drm/drm_fb_helper.h | 2 +-
2 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index ed43b987d306..7c4ab6e6f865 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -436,11 +436,11 @@ static void drm_fb_helper_damage_work(struct work_struct *work)
unsigned long flags;
int ret;
- spin_lock_irqsave(&helper->damage_lock, flags);
+ raw_spin_lock_irqsave(&helper->damage_lock, flags);
clip_copy = *clip;
clip->x1 = clip->y1 = ~0;
clip->x2 = clip->y2 = 0;
- spin_unlock_irqrestore(&helper->damage_lock, flags);
+ raw_spin_unlock_irqrestore(&helper->damage_lock, flags);
/* Call damage handlers only if necessary */
if (!(clip_copy.x1 < clip_copy.x2 && clip_copy.y1 < clip_copy.y2))
@@ -465,12 +465,12 @@ static void drm_fb_helper_damage_work(struct work_struct *work)
* Restore damage clip rectangle on errors. The next run
* of the damage worker will perform the update.
*/
- spin_lock_irqsave(&helper->damage_lock, flags);
+ raw_spin_lock_irqsave(&helper->damage_lock, flags);
clip->x1 = min_t(u32, clip->x1, clip_copy.x1);
clip->y1 = min_t(u32, clip->y1, clip_copy.y1);
clip->x2 = max_t(u32, clip->x2, clip_copy.x2);
clip->y2 = max_t(u32, clip->y2, clip_copy.y2);
- spin_unlock_irqrestore(&helper->damage_lock, flags);
+ raw_spin_unlock_irqrestore(&helper->damage_lock, flags);
}
/**
@@ -486,7 +486,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
const struct drm_fb_helper_funcs *funcs)
{
INIT_LIST_HEAD(&helper->kernel_fb_list);
- spin_lock_init(&helper->damage_lock);
+ raw_spin_lock_init(&helper->damage_lock);
INIT_WORK(&helper->resume_work, drm_fb_helper_resume_worker);
INIT_WORK(&helper->damage_work, drm_fb_helper_damage_work);
helper->damage_clip.x1 = helper->damage_clip.y1 = ~0;
@@ -670,12 +670,12 @@ static void drm_fb_helper_damage(struct fb_info *info, u32 x, u32 y,
if (!drm_fbdev_use_shadow_fb(helper))
return;
- spin_lock_irqsave(&helper->damage_lock, flags);
+ raw_spin_lock_irqsave(&helper->damage_lock, flags);
clip->x1 = min_t(u32, clip->x1, x);
clip->y1 = min_t(u32, clip->y1, y);
clip->x2 = max_t(u32, clip->x2, x + width);
clip->y2 = max_t(u32, clip->y2, y + height);
- spin_unlock_irqrestore(&helper->damage_lock, flags);
+ raw_spin_unlock_irqrestore(&helper->damage_lock, flags);
schedule_work(&helper->damage_work);
}
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index 3af4624368d8..91178958896e 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -131,7 +131,7 @@ struct drm_fb_helper {
struct fb_info *fbdev;
u32 pseudo_palette[17];
struct drm_clip_rect damage_clip;
- spinlock_t damage_lock;
+ raw_spinlock_t damage_lock;
struct work_struct damage_work;
struct work_struct resume_work;
--
Jiri Kosina
SUSE Labs