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From:   Marek Szyprowski <m.szyprowski@samsung.com>
To:     patches@opensource.cirrus.com, alsa-devel@alsa-project.org,
        linux-kernel@vger.kernel.org
Cc:     Marek Szyprowski <m.szyprowski@samsung.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        Charles Keepax <ckeepax@opensource.cirrus.com>
Subject: [PATCH] ASoC: wm8994: Fix potential deadlock
Date:   Fri,  9 Dec 2022 10:16:57 +0100
Message-Id: <20221209091657.1183-1-m.szyprowski@samsung.com>
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References: <CGME20221209091928eucas1p1cfc768d888a6e6c57fcaa0fe320cfced@eucas1p1.samsung.com>
Precedence: bulk

Commit c0feea594e05 ("workqueue: don't skip lockdep work dependency in
cancel_work_sync()") revealed the following locking issue in the wm8994
codec:

======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc1-00001-gc0feea594e05-dirty #13097 Not tainted
------------------------------------------------------
kworker/1:1/32 is trying to acquire lock:
c2bd4300 (&wm8994->accdet_lock){+.+.}-{3:3}, at: wm1811_mic_work+0x38/0xdc

but task is already holding lock:
f08f5f28 ((work_completion)(&(&wm8994->mic_work)->work)){+.+.}-{0:0}, at: process_one_work+0x1e4/0x778

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 ((work_completion)(&(&wm8994->mic_work)->work)){+.+.}-{0:0}:
       __cancel_work_timer+0x198/0x22c
       wm1811_jackdet_irq+0x124/0x238
       process_one_work+0x288/0x778
       worker_thread+0x44/0x504
       kthread+0xf0/0x124
       ret_from_fork+0x14/0x2c
       0x0

-> #0 (&wm8994->accdet_lock){+.+.}-{3:3}:
       lock_acquire+0x124/0x3e4
       __mutex_lock+0x90/0x948
       mutex_lock_nested+0x1c/0x24
       wm1811_mic_work+0x38/0xdc
       process_one_work+0x288/0x778
       worker_thread+0x44/0x504
       kthread+0xf0/0x124
       ret_from_fork+0x14/0x2c
       0x0

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((work_completion)(&(&wm8994->mic_work)->work));
                               lock(&wm8994->accdet_lock);
                               lock((work_completion)(&(&wm8994->mic_work)->work));
  lock(&wm8994->accdet_lock);

 *** DEADLOCK ***

2 locks held by kworker/1:1/32:
 #0: c1c072a8 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x1e4/0x778
 #1: f08f5f28 ((work_completion)(&(&wm8994->mic_work)->work)){+.+.}-{0:0}, at: process_one_work+0x1e4/0x778

stack backtrace:
CPU: 1 PID: 32 Comm: kworker/1:1 Not tainted 6.0.0-rc1-00001-gc0feea594e05-dirty #13097
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: events_power_efficient wm1811_mic_work
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from dump_stack_lvl+0x58/0x70
 dump_stack_lvl from check_noncircular+0xf0/0x158
 check_noncircular from __lock_acquire+0x15e8/0x2a7c
 __lock_acquire from lock_acquire+0x124/0x3e4
 lock_acquire from __mutex_lock+0x90/0x948
 __mutex_lock from mutex_lock_nested+0x1c/0x24
 mutex_lock_nested from wm1811_mic_work+0x38/0xdc
 wm1811_mic_work from process_one_work+0x288/0x778
 process_one_work from worker_thread+0x44/0x504
 worker_thread from kthread+0xf0/0x124
 kthread from ret_from_fork+0x14/0x2c
Exception stack(0xf08f5fb0 to 0xf08f5ff8)
...
--->8---

Fix this by dropping wm8994->accdet_lock while calling
cancel_delayed_work_sync(&wm8994->mic_work) in wm1811_jackdet_irq().

Fixes: c0cc3f166525 ("ASoC: wm8994: Allow a delay between jack insertion and microphone detect")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 sound/soc/codecs/wm8994.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/soc/codecs/wm8994.c b/sound/soc/codecs/wm8994.c
index d3cfd3788f2a..f810135e28d0 100644
--- a/sound/soc/codecs/wm8994.c
+++ b/sound/soc/codecs/wm8994.c
@@ -3853,7 +3853,12 @@ static irqreturn_t wm1811_jackdet_irq(int irq, void *data)
 	} else {
 		dev_dbg(component->dev, "Jack not detected\n");
 
+		/* Release wm8994->accdet_lock to avoid deadlock:
+		 * cancel_delayed_work_sync() takes wm8994->mic_work internal
+		 * lock and wm1811_mic_work takes wm8994->accdet_lock */
+		mutex_unlock(&wm8994->accdet_lock);
 		cancel_delayed_work_sync(&wm8994->mic_work);
+		mutex_lock(&wm8994->accdet_lock);
 
 		snd_soc_component_update_bits(component, WM8958_MICBIAS2,
 				    WM8958_MICB2_DISCH, WM8958_MICB2_DISCH);
-- 
2.38.1