[PATCH] nvram: Drop the bkl from nvram_llseek()

[PATCH] nvram: Drop the bkl from nvram_llseek()

[Frederic Weisbecker]

There is nothing to protect inside nvram_llseek(), the file
offset doesn't need to be protected and nvram_len is only
initialized from an __init path.

It's safe to remove the big kernel lock there.

(Is this file still used? I can't even build it,
looks like it is built under CONFIG_GENERIC_NVRAM but this
option is referenced nowhere except in powerpc defconfigs)

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: John Kacur <jkacur@redhat.com>
Cc: Sven-Thorsten Dietrich <sven@thebigcorporation.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Greg KH <gregkh@suse.de>
---
 drivers/char/generic_nvram.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/char/generic_nvram.c b/drivers/char/generic_nvram.c
index ef31738..c49200e 100644
--- a/drivers/char/generic_nvram.c
+++ b/drivers/char/generic_nvram.c
@@ -32,7 +32,6 @@ static ssize_t nvram_len;
 
 static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
 {
-	lock_kernel();
 	switch (origin) {
 	case 1:
 		offset += file->f_pos;
@@ -41,12 +40,11 @@ static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
 		offset += nvram_len;
 		break;
 	}
-	if (offset < 0) {
-		unlock_kernel();
+	if (offset < 0)
 		return -EINVAL;
-	}
+
 	file->f_pos = offset;
-	unlock_kernel();
+
 	return file->f_pos;
 }
 
-- 
1.6.2.3

Re: [PATCH] nvram: Drop the bkl from nvram_llseek()

[Thomas Gleixner]

B1;2005;0cOn Fri, 9 Oct 2009, Frederic Weisbecker wrote:

> There is nothing to protect inside nvram_llseek(), the file
> offset doesn't need to be protected and nvram_len is only
> initialized from an __init path.
> 
> It's safe to remove the big kernel lock there.
> 
> (Is this file still used? I can't even build it,
> looks like it is built under CONFIG_GENERIC_NVRAM but this
> option is referenced nowhere except in powerpc defconfigs)

Yes it is used. Look at arch/powerpc/Kconfig

config GENERIC_NVRAM
        bool
	default y if PPC32

But I have to admit that the GENERIC part is confusing :)

> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: John Kacur <jkacur@redhat.com>
> Cc: Sven-Thorsten Dietrich <sven@thebigcorporation.com>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Alessio Igor Bogani <abogani@texware.it>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Greg KH <gregkh@suse.de>

Added to the pile of pending BKL bashing. Thanks,

      tglx      

> ---
>  drivers/char/generic_nvram.c |    8 +++-----
>  1 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/char/generic_nvram.c b/drivers/char/generic_nvram.c
> index ef31738..c49200e 100644
> --- a/drivers/char/generic_nvram.c
> +++ b/drivers/char/generic_nvram.c
> @@ -32,7 +32,6 @@ static ssize_t nvram_len;
>  
>  static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
>  {
> -	lock_kernel();
>  	switch (origin) {
>  	case 1:
>  		offset += file->f_pos;
> @@ -41,12 +40,11 @@ static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
>  		offset += nvram_len;
>  		break;
>  	}
> -	if (offset < 0) {
> -		unlock_kernel();
> +	if (offset < 0)
>  		return -EINVAL;
> -	}
> +
>  	file->f_pos = offset;
> -	unlock_kernel();
> +
>  	return file->f_pos;
>  }
>  
> -- 
> 1.6.2.3
> 

Re: [PATCH] nvram: Drop the bkl from nvram_llseek()

[Frederic Weisbecker]

On Fri, Oct 09, 2009 at 09:27:17PM +0200, Thomas Gleixner wrote:
> B1;2005;0cOn Fri, 9 Oct 2009, Frederic Weisbecker wrote:
> 
> > There is nothing to protect inside nvram_llseek(), the file
> > offset doesn't need to be protected and nvram_len is only
> > initialized from an __init path.
> > 
> > It's safe to remove the big kernel lock there.
> > 
> > (Is this file still used? I can't even build it,
> > looks like it is built under CONFIG_GENERIC_NVRAM but this
> > option is referenced nowhere except in powerpc defconfigs)
> 
> Yes it is used. Look at arch/powerpc/Kconfig
> 
> config GENERIC_NVRAM
>         bool
> 	default y if PPC32


Oh right, I missed it.

 
> But I have to admit that the GENERIC part is confusing :)


Yep :)


> > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@elte.hu>
> > Cc: John Kacur <jkacur@redhat.com>
> > Cc: Sven-Thorsten Dietrich <sven@thebigcorporation.com>
> > Cc: Jonathan Corbet <corbet@lwn.net>
> > Cc: Alessio Igor Bogani <abogani@texware.it>
> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > Cc: Greg KH <gregkh@suse.de>
> 
> Added to the pile of pending BKL bashing. Thanks,
> 
>       tglx      


Ok. Be care I couldn't even build test this one.

Thanks.

[tip:bkl/drivers] nvram: Drop the bkl from nvram_llseek()

[tip-bot for Frederic Weisbecker]

Commit-ID:  6783b9cd7104470a3afab51c205c5aea53a2858f
Gitweb:     http://git.kernel.org/tip/6783b9cd7104470a3afab51c205c5aea53a2858f
Author:     Frederic Weisbecker <fweisbec@gmail.com>
AuthorDate: Fri, 9 Oct 2009 21:20:30 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 14 Oct 2009 17:36:49 +0200

nvram: Drop the bkl from nvram_llseek()

There is nothing to protect inside nvram_llseek(), the file
offset doesn't need to be protected and nvram_len is only
initialized from an __init path.

It's safe to remove the big kernel lock there.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1255116030-6929-1-git-send-email-fweisbec@gmail.com>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 drivers/char/generic_nvram.c |    9 +++------
 1 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/char/generic_nvram.c b/drivers/char/generic_nvram.c
index ef31738..fda4181 100644
--- a/drivers/char/generic_nvram.c
+++ b/drivers/char/generic_nvram.c
@@ -19,7 +19,6 @@
 #include <linux/miscdevice.h>
 #include <linux/fcntl.h>
 #include <linux/init.h>
-#include <linux/smp_lock.h>
 #include <asm/uaccess.h>
 #include <asm/nvram.h>
 #ifdef CONFIG_PPC_PMAC
@@ -32,7 +31,6 @@ static ssize_t nvram_len;
 
 static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
 {
-	lock_kernel();
 	switch (origin) {
 	case 1:
 		offset += file->f_pos;
@@ -41,12 +39,11 @@ static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
 		offset += nvram_len;
 		break;
 	}
-	if (offset < 0) {
-		unlock_kernel();
+	if (offset < 0)
 		return -EINVAL;
-	}
+
 	file->f_pos = offset;
-	unlock_kernel();
+
 	return file->f_pos;
 }