2024-06-11 11:04:59

by Ricardo Ribalda

Subject: [PATCH 2/2] media: drivers/media/dvb-core: Refactor dvb_frontend_open locking

Split out the wait function, and introduce some new toys: guard and
lockdep.

This fixes the following cocci warnings:
drivers/media/dvb-core/dvb_frontend.c:2897:1-7: preceding lock on line 2776
drivers/media/dvb-core/dvb_frontend.c:2897:1-7: preceding lock on line 2786
drivers/media/dvb-core/dvb_frontend.c:2897:1-7: preceding lock on line 2809

Signed-off-by: Ricardo Ribalda <[email protected]>
---
drivers/media/dvb-core/dvb_frontend.c | 59 ++++++++++++++++++++++-------------
1 file changed, 38 insertions(+), 21 deletions(-)

diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
index e81b9996530e..a7739f5e78cb 100644
--- a/drivers/media/dvb-core/dvb_frontend.c
+++ b/drivers/media/dvb-core/dvb_frontend.c
@@ -30,6 +30,7 @@
#include <linux/kthread.h>
#include <linux/ktime.h>
#include <linux/compat.h>
+#include <linux/lockdep.h>
#include <asm/processor.h>

#include <media/dvb_frontend.h>
@@ -2826,6 +2827,34 @@ static int __dvb_frontend_open(struct inode *inode, struct file *file)
return ret;
}

+static int wait_dvb_frontend(struct dvb_adapter *adapter,
+ struct dvb_device *mfedev)
+{
+ struct dvb_frontend *mfe = mfedev->priv;
+ struct dvb_frontend_private *mfepriv = mfe->frontend_priv;
+ int mferetry = (dvb_mfe_wait_time << 1);
+ int ret = 0;
+
+ lockdep_assert_held(&adapter->mfe_lock);
+
+ if (mfedev->users == -1 && !mfepriv->thread)
+ return 0;
+
+ mutex_unlock(&adapter->mfe_lock);
+
+ while (mferetry-- && (mfedev->users != -1 || mfepriv->thread)) {
+ if (msleep_interruptible(500))
+ if (signal_pending(current)) {
+ ret = -EINTR;
+ break;
+ }
+ }
+
+ mutex_lock(&adapter->mfe_lock);
+
+ return ret;
+}
+
static int dvb_frontend_open(struct inode *inode, struct file *file)
{
struct dvb_device *dvbdev = file->private_data;
@@ -2840,19 +2869,17 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
if (!adapter->mfe_shared)
return __dvb_frontend_open(inode, file);

+
+ guard(mutex)(&adapter->mfe_lock);
+
if (adapter->mfe_shared == 2) {
- mutex_lock(&adapter->mfe_lock);
if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
if (adapter->mfe_dvbdev &&
- !adapter->mfe_dvbdev->writers) {
- mutex_unlock(&adapter->mfe_lock);
+ !adapter->mfe_dvbdev->writers)
return -EBUSY;
- }
adapter->mfe_dvbdev = dvbdev;
}
} else {
- mutex_lock(&adapter->mfe_lock);
-
if (!adapter->mfe_dvbdev) {
adapter->mfe_dvbdev = dvbdev;
} else if (adapter->mfe_dvbdev != dvbdev) {
@@ -2862,34 +2889,24 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
*mfe = mfedev->priv;
struct dvb_frontend_private
*mfepriv = mfe->frontend_priv;
- int mferetry = (dvb_mfe_wait_time << 1);
-
- mutex_unlock(&adapter->mfe_lock);
- while (mferetry-- && (mfedev->users != -1 ||
- mfepriv->thread)) {
- if (msleep_interruptible(500)) {
- if (signal_pending(current))
- return -EINTR;
- }
- }

- mutex_lock(&adapter->mfe_lock);
+ ret = wait_dvb_frontend(adapter, mfedev);
+ if (ret)
+ return ret;
+
if (adapter->mfe_dvbdev != dvbdev) {
mfedev = adapter->mfe_dvbdev;
mfe = mfedev->priv;
mfepriv = mfe->frontend_priv;
if (mfedev->users != -1 ||
- mfepriv->thread) {
- mutex_unlock(&adapter->mfe_lock);
+ mfepriv->thread)
return -EBUSY;
- }
adapter->mfe_dvbdev = dvbdev;
}
}
}

ret = __dvb_frontend_open(inode, file);
- mutex_unlock(&adapter->mfe_lock);

return ret;
}

--
2.45.2.505.gda0bf45e8d-goog

2024-06-11 11:08:30

by Ricardo Ribalda

Subject: Re: [PATCH 2/2] media: drivers/media/dvb-core: Refactor dvb_frontend_open locking

Hi Hans

I clicked on send too fast sorry :S

CHECK: Alignment should match open parenthesis
#37: FILE: drivers/media/dvb-core/dvb_frontend.c:2831:
+static int wait_dvb_frontend(struct dvb_adapter *adapter,
+ struct dvb_device *mfedev)

CHECK: Please don't use multiple blank lines
#71: FILE: drivers/media/dvb-core/dvb_frontend.c:2872:

+

Let me know if I should resend or you can handle it while merging. I
already fixed in my tree in case I have to send a v2

Thanks!

On Tue, 11 Jun 2024 at 13:03, Ricardo Ribalda <[email protected]> wrote:
>
> Split out the wait function, and introduce some new toys: guard and
> lockdep.
>
> This fixes the following cocci warnings:
> drivers/media/dvb-core/dvb_frontend.c:2897:1-7: preceding lock on line 2776
> drivers/media/dvb-core/dvb_frontend.c:2897:1-7: preceding lock on line 2786
> drivers/media/dvb-core/dvb_frontend.c:2897:1-7: preceding lock on line 2809
>
> Signed-off-by: Ricardo Ribalda <[email protected]>
> ---
> drivers/media/dvb-core/dvb_frontend.c | 59 ++++++++++++++++++++++-------------
> 1 file changed, 38 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/media/dvb-core/dvb_frontend.c b/drivers/media/dvb-core/dvb_frontend.c
> index e81b9996530e..a7739f5e78cb 100644
> --- a/drivers/media/dvb-core/dvb_frontend.c
> +++ b/drivers/media/dvb-core/dvb_frontend.c
> @@ -30,6 +30,7 @@
> #include <linux/kthread.h>
> #include <linux/ktime.h>
> #include <linux/compat.h>
> +#include <linux/lockdep.h>
> #include <asm/processor.h>
>
> #include <media/dvb_frontend.h>
> @@ -2826,6 +2827,34 @@ static int __dvb_frontend_open(struct inode *inode, struct file *file)
> return ret;
> }
>
> +static int wait_dvb_frontend(struct dvb_adapter *adapter,
> + struct dvb_device *mfedev)
> +{
> + struct dvb_frontend *mfe = mfedev->priv;
> + struct dvb_frontend_private *mfepriv = mfe->frontend_priv;
> + int mferetry = (dvb_mfe_wait_time << 1);
> + int ret = 0;
> +
> + lockdep_assert_held(&adapter->mfe_lock);
> +
> + if (mfedev->users == -1 && !mfepriv->thread)
> + return 0;
> +
> + mutex_unlock(&adapter->mfe_lock);
> +
> + while (mferetry-- && (mfedev->users != -1 || mfepriv->thread)) {
> + if (msleep_interruptible(500))
> + if (signal_pending(current)) {
> + ret = -EINTR;
> + break;
> + }
> + }
> +
> + mutex_lock(&adapter->mfe_lock);
> +
> + return ret;
> +}
> +
> static int dvb_frontend_open(struct inode *inode, struct file *file)
> {
> struct dvb_device *dvbdev = file->private_data;
> @@ -2840,19 +2869,17 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
> if (!adapter->mfe_shared)
> return __dvb_frontend_open(inode, file);
>
> +
> + guard(mutex)(&adapter->mfe_lock);
> +
> if (adapter->mfe_shared == 2) {
> - mutex_lock(&adapter->mfe_lock);
> if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
> if (adapter->mfe_dvbdev &&
> - !adapter->mfe_dvbdev->writers) {
> - mutex_unlock(&adapter->mfe_lock);
> + !adapter->mfe_dvbdev->writers)
> return -EBUSY;
> - }
> adapter->mfe_dvbdev = dvbdev;
> }
> } else {
> - mutex_lock(&adapter->mfe_lock);
> -
> if (!adapter->mfe_dvbdev) {
> adapter->mfe_dvbdev = dvbdev;
> } else if (adapter->mfe_dvbdev != dvbdev) {
> @@ -2862,34 +2889,24 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
> *mfe = mfedev->priv;
> struct dvb_frontend_private
> *mfepriv = mfe->frontend_priv;
> - int mferetry = (dvb_mfe_wait_time << 1);
> -
> - mutex_unlock(&adapter->mfe_lock);
> - while (mferetry-- && (mfedev->users != -1 ||
> - mfepriv->thread)) {
> - if (msleep_interruptible(500)) {
> - if (signal_pending(current))
> - return -EINTR;
> - }
> - }
>
> - mutex_lock(&adapter->mfe_lock);
> + ret = wait_dvb_frontend(adapter, mfedev);
> + if (ret)
> + return ret;
> +
> if (adapter->mfe_dvbdev != dvbdev) {
> mfedev = adapter->mfe_dvbdev;
> mfe = mfedev->priv;
> mfepriv = mfe->frontend_priv;
> if (mfedev->users != -1 ||
> - mfepriv->thread) {
> - mutex_unlock(&adapter->mfe_lock);
> + mfepriv->thread)
> return -EBUSY;
> - }
> adapter->mfe_dvbdev = dvbdev;
> }
> }
> }
>
> ret = __dvb_frontend_open(inode, file);
> - mutex_unlock(&adapter->mfe_lock);
>
> return ret;
> }
>
> --
> 2.45.2.505.gda0bf45e8d-goog
>


--
Ricardo Ribalda