[PATCH 1/2] ttyprintk: Fix wrong tty_unregister_driver() call in the error path

[PATCH 1/2] ttyprintk: Fix wrong tty_unregister_driver() call in the error path

[Takashi Iwai]

ttyprintk driver calls tty_unregister_driver() wrongly in the error
path of tty_register_driver().  Also, setting ttyprintk_driver to NULL
is utterly superfluous, so let's get rid of it, too.

Reported-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 drivers/char/ttyprintk.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
index daea84c41743..2a39c5790364 100644
--- a/drivers/char/ttyprintk.c
+++ b/drivers/char/ttyprintk.c
@@ -210,10 +210,8 @@ static int __init ttyprintk_init(void)
 	return 0;
 
 error:
-	tty_unregister_driver(ttyprintk_driver);
 	put_tty_driver(ttyprintk_driver);
 	tty_port_destroy(&tpk_port.port);
-	ttyprintk_driver = NULL;
 	return ret;
 }
 device_initcall(ttyprintk_init);
-- 
1.9.1

[PATCH 2/2] ttyprintk: Allow built as a module

[Takashi Iwai]

The driver is well written to be used as a module, just the exit call
is missing.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 drivers/char/Kconfig     |  2 +-
 drivers/char/ttyprintk.c | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 1386749b48ff..97816b133c7f 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -40,7 +40,7 @@ config SGI_MBCS
 source "drivers/tty/serial/Kconfig"
 
 config TTY_PRINTK
-	bool "TTY driver to output user messages via printk"
+	tristate "TTY driver to output user messages via printk"
 	depends on EXPERT && TTY
 	default n
 	---help---
diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
index 2a39c5790364..73606eaaba71 100644
--- a/drivers/char/ttyprintk.c
+++ b/drivers/char/ttyprintk.c
@@ -17,7 +17,7 @@
 #include <linux/device.h>
 #include <linux/serial.h>
 #include <linux/tty.h>
-#include <linux/export.h>
+#include <linux/module.h>
 
 struct ttyprintk_port {
 	struct tty_port port;
@@ -214,4 +214,15 @@ error:
 	tty_port_destroy(&tpk_port.port);
 	return ret;
 }
+
+static void ttyprintk_exit(void)
+{
+	tty_unregister_driver(ttyprintk_driver);
+	put_tty_driver(ttyprintk_driver);
+	tty_port_destroy(&tpk_port.port);
+}
+
 device_initcall(ttyprintk_init);
+module_exit(ttyprintk_exit);
+
+MODULE_LICENSE("GPL");
-- 
1.9.1

Re: [PATCH 1/2] ttyprintk: Fix wrong tty_unregister_driver() call in the error path

[Jean Delvare]

Le Wednesday 02 April 2014 à 12:29 +0200, Takashi Iwai a écrit :
> ttyprintk driver calls tty_unregister_driver() wrongly in the error
> path of tty_register_driver().  Also, setting ttyprintk_driver to NULL
> is utterly superfluous, so let's get rid of it, too.
> 
> Reported-by: Jean Delvare <jdelvare@suse.de>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
>  drivers/char/ttyprintk.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
> index daea84c41743..2a39c5790364 100644
> --- a/drivers/char/ttyprintk.c
> +++ b/drivers/char/ttyprintk.c
> @@ -210,10 +210,8 @@ static int __init ttyprintk_init(void)
>  	return 0;
>  
>  error:
> -	tty_unregister_driver(ttyprintk_driver);
>  	put_tty_driver(ttyprintk_driver);
>  	tty_port_destroy(&tpk_port.port);
> -	ttyprintk_driver = NULL;
>  	return ret;
>  }
>  device_initcall(ttyprintk_init);

Reviewed-by: Jean Delvare <jdelvare@suse.de>

-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH 2/2] ttyprintk: Allow built as a module

[Jean Delvare]

Hi Takashi,

Le Wednesday 02 April 2014 à 12:29 +0200, Takashi Iwai a écrit :
> The driver is well written to be used as a module, just the exit call
> is missing.
> 
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
>  drivers/char/Kconfig     |  2 +-
>  drivers/char/ttyprintk.c | 13 ++++++++++++-
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
> index 1386749b48ff..97816b133c7f 100644
> --- a/drivers/char/Kconfig
> +++ b/drivers/char/Kconfig
> @@ -40,7 +40,7 @@ config SGI_MBCS
>  source "drivers/tty/serial/Kconfig"
>  
>  config TTY_PRINTK
> -	bool "TTY driver to output user messages via printk"
> +	tristate "TTY driver to output user messages via printk"
>  	depends on EXPERT && TTY
>  	default n
>  	---help---
> diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
> index 2a39c5790364..73606eaaba71 100644
> --- a/drivers/char/ttyprintk.c
> +++ b/drivers/char/ttyprintk.c
> @@ -17,7 +17,7 @@
>  #include <linux/device.h>
>  #include <linux/serial.h>
>  #include <linux/tty.h>
> -#include <linux/export.h>
> +#include <linux/module.h>
>  
>  struct ttyprintk_port {
>  	struct tty_port port;
> @@ -214,4 +214,15 @@ error:
>  	tty_port_destroy(&tpk_port.port);
>  	return ret;
>  }
> +
> +static void ttyprintk_exit(void)

Could be marked __exit.

> +{
> +	tty_unregister_driver(ttyprintk_driver);
> +	put_tty_driver(ttyprintk_driver);
> +	tty_port_destroy(&tpk_port.port);
> +}
> +
>  device_initcall(ttyprintk_init);
> +module_exit(ttyprintk_exit);
> +
> +MODULE_LICENSE("GPL");

Other than this, this looks good, thanks for doing that.

Reviewed-by: Jean Delvare <jdelvare@suse.de>

-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH 2/2] ttyprintk: Allow built as a module

[Takashi Iwai]

At Wed, 02 Apr 2014 14:31:46 +0200,
Jean Delvare wrote:
> 
> Hi Takashi,
> 
> Le Wednesday 02 April 2014 à 12:29 +0200, Takashi Iwai a écrit :
> > The driver is well written to be used as a module, just the exit call
> > is missing.
> > 
> > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > ---
> >  drivers/char/Kconfig     |  2 +-
> >  drivers/char/ttyprintk.c | 13 ++++++++++++-
> >  2 files changed, 13 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
> > index 1386749b48ff..97816b133c7f 100644
> > --- a/drivers/char/Kconfig
> > +++ b/drivers/char/Kconfig
> > @@ -40,7 +40,7 @@ config SGI_MBCS
> >  source "drivers/tty/serial/Kconfig"
> >  
> >  config TTY_PRINTK
> > -	bool "TTY driver to output user messages via printk"
> > +	tristate "TTY driver to output user messages via printk"
> >  	depends on EXPERT && TTY
> >  	default n
> >  	---help---
> > diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
> > index 2a39c5790364..73606eaaba71 100644
> > --- a/drivers/char/ttyprintk.c
> > +++ b/drivers/char/ttyprintk.c
> > @@ -17,7 +17,7 @@
> >  #include <linux/device.h>
> >  #include <linux/serial.h>
> >  #include <linux/tty.h>
> > -#include <linux/export.h>
> > +#include <linux/module.h>
> >  
> >  struct ttyprintk_port {
> >  	struct tty_port port;
> > @@ -214,4 +214,15 @@ error:
> >  	tty_port_destroy(&tpk_port.port);
> >  	return ret;
> >  }
> > +
> > +static void ttyprintk_exit(void)
> 
> Could be marked __exit.
> 
> > +{
> > +	tty_unregister_driver(ttyprintk_driver);
> > +	put_tty_driver(ttyprintk_driver);
> > +	tty_port_destroy(&tpk_port.port);
> > +}
> > +
> >  device_initcall(ttyprintk_init);
> > +module_exit(ttyprintk_exit);
> > +
> > +MODULE_LICENSE("GPL");
> 
> Other than this, this looks good, thanks for doing that.
> 
> Reviewed-by: Jean Delvare <jdelvare@suse.de>

Thanks!  I'll resubmit the fixed patch.


Takashi

Re: [PATCH 2/2] ttyprintk: Allow built as a module

[Greg Kroah-Hartman]

On Wed, Apr 02, 2014 at 12:29:42PM +0200, Takashi Iwai wrote:
> The driver is well written to be used as a module, just the exit call
> is missing.
> 
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
>  drivers/char/Kconfig     |  2 +-
>  drivers/char/ttyprintk.c | 13 ++++++++++++-
>  2 files changed, 13 insertions(+), 2 deletions(-)

There was some reason we didn't do this back when the code was accepted,
but I really can't remember why.

If you have tested this out, I don't have any objections to taking these
patches, thanks.

greg k-h

Re: [PATCH 1/2] ttyprintk: Fix wrong tty_unregister_driver() call in the error path

[Takashi Iwai]

At Wed, 02 Apr 2014 14:24:33 +0200,
Jean Delvare wrote:
> 
> Le Wednesday 02 April 2014 à 12:29 +0200, Takashi Iwai a écrit :
> > ttyprintk driver calls tty_unregister_driver() wrongly in the error
> > path of tty_register_driver().  Also, setting ttyprintk_driver to NULL
> > is utterly superfluous, so let's get rid of it, too.
> > 
> > Reported-by: Jean Delvare <jdelvare@suse.de>
> > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > ---
> >  drivers/char/ttyprintk.c | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
> > index daea84c41743..2a39c5790364 100644
> > --- a/drivers/char/ttyprintk.c
> > +++ b/drivers/char/ttyprintk.c
> > @@ -210,10 +210,8 @@ static int __init ttyprintk_init(void)
> >  	return 0;
> >  
> >  error:
> > -	tty_unregister_driver(ttyprintk_driver);
> >  	put_tty_driver(ttyprintk_driver);
> >  	tty_port_destroy(&tpk_port.port);
> > -	ttyprintk_driver = NULL;
> >  	return ret;
> >  }
> >  device_initcall(ttyprintk_init);
> 
> Reviewed-by: Jean Delvare <jdelvare@suse.de>

Meanwhile, I found that tty_unregister_driver() was added
intentionally in the commit f06fb543c1d0,
    TTY: ttyprintk, unregister tty driver on failure
    
    When the tty_printk driver fails to create a node in sysfs, the
    system
    crashes. It is because the driver registers a tty driver and frees
    it
    without deregistering it first. The fix is easy: add a call to
    tty_unregister_driver to the fail path.

But, I failed to see why this is needed in the current code.

Jiri, is your fix still valid at all?


thanks,

Takashi

Re: [PATCH 2/2] ttyprintk: Allow built as a module

[Takashi Iwai]

At Wed, 2 Apr 2014 12:32:22 -0700,
Greg Kroah-Hartman wrote:
> 
> On Wed, Apr 02, 2014 at 12:29:42PM +0200, Takashi Iwai wrote:
> > The driver is well written to be used as a module, just the exit call
> > is missing.
> > 
> > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > ---
> >  drivers/char/Kconfig     |  2 +-
> >  drivers/char/ttyprintk.c | 13 ++++++++++++-
> >  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> There was some reason we didn't do this back when the code was accepted,
> but I really can't remember why.
> 
> If you have tested this out, I don't have any objections to taking these
> patches, thanks.

The module worked fine with my quick tests (load/unload/feed something
via /dev/ttyprintk), at least.  But it'd be helpful if anyone
remembers and clarifies.


thanks,

Takashi

Re: [PATCH 1/2] ttyprintk: Fix wrong tty_unregister_driver() call in the error path

[Jiri Slaby]

On 04/03/2014 08:10 AM, Takashi Iwai wrote:
> At Wed, 02 Apr 2014 14:24:33 +0200,
> Jean Delvare wrote:
>>
>> Le Wednesday 02 April 2014 à 12:29 +0200, Takashi Iwai a écrit :
>>> ttyprintk driver calls tty_unregister_driver() wrongly in the error
>>> path of tty_register_driver().  Also, setting ttyprintk_driver to NULL
>>> is utterly superfluous, so let's get rid of it, too.
>>>
>>> Reported-by: Jean Delvare <jdelvare@suse.de>
>>> Signed-off-by: Takashi Iwai <tiwai@suse.de>
>>> ---
>>>  drivers/char/ttyprintk.c | 2 --
>>>  1 file changed, 2 deletions(-)
>>>
>>> diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
>>> index daea84c41743..2a39c5790364 100644
>>> --- a/drivers/char/ttyprintk.c
>>> +++ b/drivers/char/ttyprintk.c
>>> @@ -210,10 +210,8 @@ static int __init ttyprintk_init(void)
>>>  	return 0;
>>>  
>>>  error:
>>> -	tty_unregister_driver(ttyprintk_driver);
>>>  	put_tty_driver(ttyprintk_driver);
>>>  	tty_port_destroy(&tpk_port.port);
>>> -	ttyprintk_driver = NULL;
>>>  	return ret;
>>>  }
>>>  device_initcall(ttyprintk_init);
>>
>> Reviewed-by: Jean Delvare <jdelvare@suse.de>
> 
> Meanwhile, I found that tty_unregister_driver() was added
> intentionally in the commit f06fb543c1d0,
>     TTY: ttyprintk, unregister tty driver on failure
>     
>     When the tty_printk driver fails to create a node in sysfs, the
>     system
>     crashes. It is because the driver registers a tty driver and frees
>     it
>     without deregistering it first. The fix is easy: add a call to
>     tty_unregister_driver to the fail path.
> 
> But, I failed to see why this is needed in the current code.
> 
> Jiri, is your fix still valid at all?

The code was different. There was also device_create after
tty_register_driver. I must admit that I don't know why I didn't change
'goto error' in the tty_register_driver fail path.

        ret = tty_register_driver(ttyprintk_driver);
        if (ret < 0) {
                printk(KERN_ERR "Couldn't register ttyprintk driver\n");
                goto error;
        }

        /* create our unnumbered device */
        rp = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 3), NULL,
                                ttyprintk_driver->name);
        if (IS_ERR(rp)) {
                printk(KERN_ERR "Couldn't create ttyprintk device\n");
                ret = PTR_ERR(rp);
                goto error;
        }



So yes, there should be no tty_unregister_driver in the fail path when
device_create is gone now.

thanks,
-- 
js
suse labs

Re: [PATCH 2/2] ttyprintk: Allow built as a module

[Samo Pogačnik]

Dne 03.04.2014 (čet) ob 08:13 +0200 je Takashi Iwai napisal(a):
> At Wed, 2 Apr 2014 12:32:22 -0700,
> Greg Kroah-Hartman wrote:
> > 
> > On Wed, Apr 02, 2014 at 12:29:42PM +0200, Takashi Iwai wrote:
> > > The driver is well written to be used as a module, just the exit call
> > > is missing.
> > > 
> > > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > > ---
> > >  drivers/char/Kconfig     |  2 +-
> > >  drivers/char/ttyprintk.c | 13 ++++++++++++-
> > >  2 files changed, 13 insertions(+), 2 deletions(-)
> > 
> > There was some reason we didn't do this back when the code was accepted,
> > but I really can't remember why.
> > 
> > If you have tested this out, I don't have any objections to taking these
> > patches, thanks.
> 
> The module worked fine with my quick tests (load/unload/feed something
> via /dev/ttyprintk), at least.  But it'd be helpful if anyone
> remembers and clarifies.
> 
My initial requirement was to be able to use this functionality as soon
as possible at the beginning of user-space initialisation, so i never
thought of the ttyprintk code being loaded afterwards as module. Also
nobody brought modularisation subject to the table during code
acceptance.

> 
> thanks,
> 
> Takashi

regards, Samo