[PATCH] TPM: update char dev BKL pushdown

[PATCH] TPM: update char dev BKL pushdown

[Rajiv Andrade]

This patch removes the BKL calls from the TPM driver, which
were added in the overall misc-char-dev-BKL-pushdown.patch,
as they are not needed. Changed num_opens from an int to atomic_t.

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>

---
 drivers/char/tpm/tpm.c |   22 +++++++---------------
 drivers/char/tpm/tpm.h |    2 +-
 2 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index ae766d8..cd4ff36 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -960,7 +960,6 @@ int tpm_open(struct inode *inode, struct file *file)
 	int rc = 0, minor = iminor(inode);
 	struct tpm_chip *chip = NULL, *pos;
 
-	lock_kernel();
 	spin_lock(&driver_lock);
 
 	list_for_each_entry(pos, &tpm_chip_list, list) {
@@ -975,34 +974,31 @@ int tpm_open(struct inode *inode, struct file *file)
 		goto err_out;
 	}
 
-	if (chip->num_opens) {
+	if (atomic_read(&chip->num_opens)) {
 		dev_dbg(chip->dev, "Another process owns this TPM\n");
 		rc = -EBUSY;
 		goto err_out;
 	}
 
-	chip->num_opens++;
+	atomic_inc(&chip->num_opens);
 	get_device(chip->dev);
 
 	spin_unlock(&driver_lock);
 
 	chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL);
 	if (chip->data_buffer == NULL) {
-		chip->num_opens--;
+		atomic_dec(&chip->num_opens);
 		put_device(chip->dev);
-		unlock_kernel();
 		return -ENOMEM;
 	}
 
 	atomic_set(&chip->data_pending, 0);
 
 	file->private_data = chip;
-	unlock_kernel();
 	return 0;
 
 err_out:
 	spin_unlock(&driver_lock);
-	unlock_kernel();
 	return rc;
 }
 EXPORT_SYMBOL_GPL(tpm_open);
@@ -1016,7 +1012,7 @@ int tpm_release(struct inode *inode, struct file *file)
 	file->private_data = NULL;
 	del_singleshot_timer_sync(&chip->user_read_timer);
 	atomic_set(&chip->data_pending, 0);
-	chip->num_opens--;
+	atomic_dec(chip->num_opens);
 	put_device(chip->dev);
 	kfree(chip->data_buffer);
 	spin_unlock(&driver_lock);
@@ -1231,20 +1227,16 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend
 		return NULL;
 	}
 
-	spin_lock(&driver_lock);
-
-	list_add(&chip->list, &tpm_chip_list);
-
-	spin_unlock(&driver_lock);
-
 	if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) {
-		list_del(&chip->list);
 		misc_deregister(&chip->vendor.miscdev);
 		put_device(chip->dev);
 		return NULL;
 	}
 
 	chip->bios_dir = tpm_bios_log_setup(devname);
+	spin_lock(&driver_lock);
+	list_add(&chip->list, &tpm_chip_list);
+	spin_unlock(&driver_lock);
 
 	return chip;
 }
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index e885148..edb8ed6 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -90,7 +90,7 @@ struct tpm_chip {
 	struct device *dev;	/* Device stuff */
 
 	int dev_num;		/* /dev/tpm# */
-	int num_opens;		/* only one allowed */
+	atomic_t num_opens;		/* only one allowed */
 	int time_expired;
 
 	/* Data passed to and from the tpm via the read/write calls */
-- 
1.5.4.5

Re: [PATCH] TPM: update char dev BKL pushdown

[Serge E. Hallyn]

Quoting Rajiv Andrade (srajiv@linux.vnet.ibm.com):
> This patch removes the BKL calls from the TPM driver, which
> were added in the overall misc-char-dev-BKL-pushdown.patch,
> as they are not needed. Changed num_opens from an int to atomic_t.
> 
> Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
> Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>

Yes, this patch is good.  

It would also be good to rename num_opens.  Note that it is always
either 0 or 1, and indicates whether someone has opened the chip.
So 'is_open' may make more sense.

Mimi is also working on a patch (on top of this one) to use rcu
to protect chip->list, and that patch will (I hope) include an
explanation of all of the locking/protection involved.

Acked-by: Serge Hallyn <serue@us.ibm.com>

> ---
>  drivers/char/tpm/tpm.c |   22 +++++++---------------
>  drivers/char/tpm/tpm.h |    2 +-
>  2 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> index ae766d8..cd4ff36 100644
> --- a/drivers/char/tpm/tpm.c
> +++ b/drivers/char/tpm/tpm.c
> @@ -960,7 +960,6 @@ int tpm_open(struct inode *inode, struct file *file)
>  	int rc = 0, minor = iminor(inode);
>  	struct tpm_chip *chip = NULL, *pos;
> 
> -	lock_kernel();
>  	spin_lock(&driver_lock);
> 
>  	list_for_each_entry(pos, &tpm_chip_list, list) {
> @@ -975,34 +974,31 @@ int tpm_open(struct inode *inode, struct file *file)
>  		goto err_out;
>  	}
> 
> -	if (chip->num_opens) {
> +	if (atomic_read(&chip->num_opens)) {
>  		dev_dbg(chip->dev, "Another process owns this TPM\n");
>  		rc = -EBUSY;
>  		goto err_out;
>  	}
> 
> -	chip->num_opens++;
> +	atomic_inc(&chip->num_opens);
>  	get_device(chip->dev);
> 
>  	spin_unlock(&driver_lock);
> 
>  	chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL);
>  	if (chip->data_buffer == NULL) {
> -		chip->num_opens--;
> +		atomic_dec(&chip->num_opens);
>  		put_device(chip->dev);
> -		unlock_kernel();
>  		return -ENOMEM;
>  	}
> 
>  	atomic_set(&chip->data_pending, 0);
> 
>  	file->private_data = chip;
> -	unlock_kernel();
>  	return 0;
> 
>  err_out:
>  	spin_unlock(&driver_lock);
> -	unlock_kernel();
>  	return rc;
>  }
>  EXPORT_SYMBOL_GPL(tpm_open);
> @@ -1016,7 +1012,7 @@ int tpm_release(struct inode *inode, struct file *file)
>  	file->private_data = NULL;
>  	del_singleshot_timer_sync(&chip->user_read_timer);
>  	atomic_set(&chip->data_pending, 0);
> -	chip->num_opens--;
> +	atomic_dec(chip->num_opens);
>  	put_device(chip->dev);
>  	kfree(chip->data_buffer);
>  	spin_unlock(&driver_lock);
> @@ -1231,20 +1227,16 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend
>  		return NULL;
>  	}
> 
> -	spin_lock(&driver_lock);
> -
> -	list_add(&chip->list, &tpm_chip_list);
> -
> -	spin_unlock(&driver_lock);
> -
>  	if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) {
> -		list_del(&chip->list);
>  		misc_deregister(&chip->vendor.miscdev);
>  		put_device(chip->dev);
>  		return NULL;
>  	}
> 
>  	chip->bios_dir = tpm_bios_log_setup(devname);
> +	spin_lock(&driver_lock);
> +	list_add(&chip->list, &tpm_chip_list);
> +	spin_unlock(&driver_lock);
> 
>  	return chip;
>  }
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index e885148..edb8ed6 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -90,7 +90,7 @@ struct tpm_chip {
>  	struct device *dev;	/* Device stuff */
> 
>  	int dev_num;		/* /dev/tpm# */
> -	int num_opens;		/* only one allowed */
> +	atomic_t num_opens;		/* only one allowed */
>  	int time_expired;
> 
>  	/* Data passed to and from the tpm via the read/write calls */
> -- 
> 1.5.4.5
> 
> 

Re: [PATCH] TPM: update char dev BKL pushdown

[James Morris]

On Fri, 22 Aug 2008, Serge E. Hallyn wrote:

> Quoting Rajiv Andrade (srajiv@linux.vnet.ibm.com):
> > This patch removes the BKL calls from the TPM driver, which
> > were added in the overall misc-char-dev-BKL-pushdown.patch,
> > as they are not needed. Changed num_opens from an int to atomic_t.
> > 
> > Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
> > Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>
> 
> Yes, this patch is good.  
> 
> It would also be good to rename num_opens.  Note that it is always
> either 0 or 1, and indicates whether someone has opened the chip.
> So 'is_open' may make more sense.

And use atomic_set() instead of atomic_inc().



- James
-- 
James Morris
<jmorris@namei.org>