2020-06-01 03:48:23

by Michał Mirosław

Subject: [PATCH] misc: atmel-ssc: lock with mutex instead of spinlock

Uninterruptible context is not needed in the driver and causes lockdep
warning because of mutex taken in of_alias_get_id(). Convert the lock to
mutex to avoid the issue.

Cc: [email protected]
Signed-off-by: Michał Mirosław <[email protected]>
---
drivers/misc/atmel-ssc.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/misc/atmel-ssc.c b/drivers/misc/atmel-ssc.c
index 1322e29bc37a..5cc032097476 100644
--- a/drivers/misc/atmel-ssc.c
+++ b/drivers/misc/atmel-ssc.c
@@ -10,7 +10,7 @@
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
-#include <linux/spinlock.h>
+#include <linux/mutex.h>
#include <linux/atmel-ssc.h>
#include <linux/slab.h>
#include <linux/module.h>
@@ -20,7 +20,7 @@
#include "../../sound/soc/atmel/atmel_ssc_dai.h"

/* Serialize access to ssc_list and user count */
-static DEFINE_SPINLOCK(user_lock);
+static DEFINE_MUTEX(user_lock);
static LIST_HEAD(ssc_list);

struct ssc_device *ssc_request(unsigned int ssc_num)
@@ -28,7 +28,7 @@ struct ssc_device *ssc_request(unsigned int ssc_num)
int ssc_valid = 0;
struct ssc_device *ssc;

- spin_lock(&user_lock);
+ mutex_lock(&user_lock);
list_for_each_entry(ssc, &ssc_list, list) {
if (ssc->pdev->dev.of_node) {
if (of_alias_get_id(ssc->pdev->dev.of_node, "ssc")
@@ -44,18 +44,18 @@ struct ssc_device *ssc_request(unsigned int ssc_num)
}

if (!ssc_valid) {
- spin_unlock(&user_lock);
+ mutex_unlock(&user_lock);
pr_err("ssc: ssc%d platform device is missing\n", ssc_num);
return ERR_PTR(-ENODEV);
}

if (ssc->user) {
- spin_unlock(&user_lock);
+ mutex_unlock(&user_lock);
dev_dbg(&ssc->pdev->dev, "module busy\n");
return ERR_PTR(-EBUSY);
}
ssc->user++;
- spin_unlock(&user_lock);
+ mutex_unlock(&user_lock);

clk_prepare(ssc->clk);

@@ -67,14 +67,14 @@ void ssc_free(struct ssc_device *ssc)
{
bool disable_clk = true;

- spin_lock(&user_lock);
+ mutex_lock(&user_lock);
if (ssc->user)
ssc->user--;
else {
disable_clk = false;
dev_dbg(&ssc->pdev->dev, "device already free\n");
}
- spin_unlock(&user_lock);
+ mutex_unlock(&user_lock);

if (disable_clk)
clk_unprepare(ssc->clk);
@@ -246,9 +246,9 @@ static int ssc_probe(struct platform_device *pdev)
return -ENXIO;
}

- spin_lock(&user_lock);
+ mutex_lock(&user_lock);
list_add_tail(&ssc->list, &ssc_list);
- spin_unlock(&user_lock);
+ mutex_unlock(&user_lock);

platform_set_drvdata(pdev, ssc);

@@ -267,9 +267,9 @@ static int ssc_remove(struct platform_device *pdev)

ssc_sound_dai_remove(ssc);

- spin_lock(&user_lock);
+ mutex_lock(&user_lock);
list_del(&ssc->list);
- spin_unlock(&user_lock);
+ mutex_unlock(&user_lock);

return 0;
}
--
2.20.1

2020-06-01 09:22:23

by Markus Elfring

Subject: Re: [PATCH] misc: atmel-ssc: lock with mutex instead of spinlock

> Uninterruptible context is not needed in the driver and causes lockdep
> warning because of mutex taken in of_alias_get_id().

Was a spin lock taken?


> Convert the lock to mutex to avoid the issue.

Would you like to add the tag “Fixes” to the commit message?

Regards,
Markus

2020-06-01 17:33:48

by Michał Mirosław

Subject: Re: [PATCH] misc: atmel-ssc: lock with mutex instead of spinlock

On Mon, Jun 01, 2020 at 11:18:48AM +0200, Markus Elfring wrote:
> > Uninterruptible context is not needed in the driver and causes lockdep
> > warning because of mutex taken in of_alias_get_id().
>
> Was a spin lock taken?
> > Convert the lock to mutex to avoid the issue.
> Would you like to add the tag “Fixes” to the commit message?

I guess we can add:

Fixes: 099343c64e16 ("ARM: at91: atmel-ssc: add device tree support")

Best Regards
Michał Mirosław