Re: [PATCH] ssb:: use put_device() if device_register fail

[arvindY]

On Wednesday 07 March 2018 11:08 PM, Michael Büsch wrote:

On Wed, 7 Mar 2018 22:46:14 +0530
arvindY  wrote:

diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
index 65420a9..c4449e0 100644
--- a/drivers/ssb/main.c
+++ b/drivers/ssb/main.c
@@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
ssb_err("Could not register %s\n", dev_name(dev));
/* Set dev to NULL to not unregister
 * dev on error unwinding. */
+   put_device(dev);
sdev->dev = NULL;
kfree(devwrap);
goto error;

I don't think this is correct.
The dev structure is allocated as part of devwrap, which is freed here.

Why do you think we need put_device here?
  

Yes this patch is not correct, We must not use kfree() after you called
device_register() (even
if it was not successful!) -- see the comment for device_register().
I will delete kfree() and send updated patch.


Is device_put() going to call ssb_release_dev() to free the structure?

Can you please elaborate on why device_put() must be used? The comment
is not really of any use here.

put_device() will call kobject_put(). By calling this, The kobject core 
will automatically
clean up all of the memory allocated with the kobject. Internally 
kobject_put() will call
kobject_cleanup() which is responsible to call 'dev -> release' and also 
free other
kobject resources. we should always avoid kfree() if device_register() 
returned an error.

Otherwise it'll not do clean up of other kobject resources.

~arvind

Re: [PATCH] ssb:: use put_device() if device_register fail

[Michael Büsch]

On Wed, 7 Mar 2018 22:46:14 +0530
arvindY  wrote:
> >> diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
> >> index 65420a9..c4449e0 100644
> >> --- a/drivers/ssb/main.c
> >> +++ b/drivers/ssb/main.c
> >> @@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
> >>ssb_err("Could not register %s\n", dev_name(dev));
> >>/* Set dev to NULL to not unregister
> >> * dev on error unwinding. */
> >> +  put_device(dev);
> >>sdev->dev = NULL;
> >>kfree(devwrap);
> >>goto error;  
> >
> > I don't think this is correct.
> > The dev structure is allocated as part of devwrap, which is freed here.
> >
> > Why do you think we need put_device here?
> >  
> Yes this patch is not correct, We must not use kfree() after you called 
> device_register() (even
> if it was not successful!) -- see the comment for device_register().
> I will delete kfree() and send updated patch.


Is device_put() going to call ssb_release_dev() to free the structure?

Can you please elaborate on why device_put() must be used? The comment
is not really of any use here.

-- 
Michael


pgp9IEPbSlMjr.pgp
Description: OpenPGP digital signature

Re: [PATCH] ssb:: use put_device() if device_register fail

[arvindY]

On Wednesday 07 March 2018 10:17 PM, Michael Büsch wrote:

On Wed,  7 Mar 2018 15:31:30 +0530
Arvind Yadav  wrote:


if device_register() returned an error! Always use put_device()
to give up the reference initialized.

Signed-off-by: Arvind Yadav 
---
  drivers/ssb/main.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
index 65420a9..c4449e0 100644
--- a/drivers/ssb/main.c
+++ b/drivers/ssb/main.c
@@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
ssb_err("Could not register %s\n", dev_name(dev));
/* Set dev to NULL to not unregister
 * dev on error unwinding. */
+   put_device(dev);
sdev->dev = NULL;
kfree(devwrap);
goto error;


I don't think this is correct.
The dev structure is allocated as part of devwrap, which is freed here.

Why do you think we need put_device here?

Yes this patch is not correct, We must not use kfree() after you called 
device_register() (even

if it was not successful!) -- see the comment for device_register().
I will delete kfree() and send updated patch.

~arvind

Re: [PATCH] ssb:: use put_device() if device_register fail

[Michael Büsch]

On Wed,  7 Mar 2018 15:31:30 +0530
Arvind Yadav  wrote:

> if device_register() returned an error! Always use put_device()
> to give up the reference initialized.
> 
> Signed-off-by: Arvind Yadav 
> ---
>  drivers/ssb/main.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
> index 65420a9..c4449e0 100644
> --- a/drivers/ssb/main.c
> +++ b/drivers/ssb/main.c
> @@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
>   ssb_err("Could not register %s\n", dev_name(dev));
>   /* Set dev to NULL to not unregister
>* dev on error unwinding. */
> + put_device(dev);
>   sdev->dev = NULL;
>   kfree(devwrap);
>   goto error;


I don't think this is correct.
The dev structure is allocated as part of devwrap, which is freed here.

Why do you think we need put_device here?

-- 
Michael


pgp9lFUSVai7N.pgp
Description: OpenPGP digital signature

[PATCH] ssb:: use put_device() if device_register fail

[Arvind Yadav]

if device_register() returned an error! Always use put_device()
to give up the reference initialized.

Signed-off-by: Arvind Yadav 
---
 drivers/ssb/main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/ssb/main.c b/drivers/ssb/main.c
index 65420a9..c4449e0 100644
--- a/drivers/ssb/main.c
+++ b/drivers/ssb/main.c
@@ -521,6 +521,7 @@ static int ssb_devices_register(struct ssb_bus *bus)
ssb_err("Could not register %s\n", dev_name(dev));
/* Set dev to NULL to not unregister
 * dev on error unwinding. */
+   put_device(dev);
sdev->dev = NULL;
kfree(devwrap);
goto error;
-- 
1.9.1