TPM: update char dev BKL pushdown

PATCH In review Rajiv Andrade 3 participants 5 messages Aug 26, 2008 – Aug 27, 2008 TPM device driver

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Rajiv Andrade

author

2008-08-26 21:00 UTC #0 lore raw

PATCH 1/1 TPM: update char dev BKL pushdown

Now considering the num_opens to is_open change and the use of atomic_set instead of atomic_dec and atomic_inc. This also includes additional comments on tpm_open.

Signed-off-by Mimi Zohar <[email protected]>

Signed-off-by Rajiv Andrade <[email protected]>

---
 drivers/char/tpm/tpm.c |   35 ++++++++++++++++++-----------------
 drivers/char/tpm/tpm.h |    2 +-
 2 files changed, 19 insertions(+), 18 deletions(-)

drivers/char/tpm/tpm.c +18 ~~-17~~

index ae766d8..09829f3 100644
@@ -954,13 +954,16 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel);
 
 /*
  * Device file system interface to the TPM
+ *
+ * It's assured that the chip will be opened just once,
+ * by the check of is_open variable, which is protected
+ * by driver_lock.
  */
 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 +978,31 @@ int tpm_open(struct inode *inode, struct file *file)
 		goto err_out;
 	}
 
-	if (chip->num_opens) {
+	if (atomic_read(&chip->is_open)) {
 		dev_dbg(chip->dev, "Another process owns this TPM\n");
 		rc = -EBUSY;
 		goto err_out;
 	}
 
-	chip->num_opens++;
-	get_device(chip->dev);
+	atomic_set(&chip->is_open, 1);
+	get_device(chip->dev); /* protect from chip disappearing */
 
 	spin_unlock(&driver_lock);
 
 	chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL);
 	if (chip->data_buffer == NULL) {
-		chip->num_opens--;
+		atomic_set(&chip->is_open, 0);
 		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 +1016,7 @@ 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_set(&chip->is_open, 0);
 	put_device(chip->dev);
 	kfree(chip->data_buffer);
 	spin_unlock(&driver_lock);

@@ -1082,7 +1082,12 @@ ssize_t tpm_read(struct file *file, char __user *buf,
 	return ret_size;
 }
 EXPORT_SYMBOL_GPL(tpm_read);
-
+/*
+ *   Called on unloading the driver.
+ *
+ *   First part unloading the chip is done here. The remainder
+ *   is done, when the device count reaches 0, in tpm_dev_release().
+ */
 void tpm_remove_hardware(struct device *dev)
 {
 	struct tpm_chip *chip = dev_get_drvdata(dev);

@@ -1231,20 +1236,16 @@ 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;
 }

drivers/char/tpm/tpm.h +1 -1

index e885148..7e0d3fb 100644
@@ -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 is_open;	/* only one allowed */
 	int time_expired;
 
 	/* Data passed to and from the tpm via the read/write calls */

Signature · 1 line

1.5.4.5

Serge E. Hallyn

Acked-by on v1 1/1

2008-08-26 21:29 UTC #1 lore raw

Quoted 6 lines · Rajiv Andrade

Now considering the num_opens to is_open change and the use of atomic_set instead of atomic_dec and atomic_inc. This also includes additional comments on tpm_open.
Signed-off-by Mimi Zohar <[email protected]>
Signed-off-by Rajiv Andrade <[email protected]>

Acked-by Serge Hallyn <[email protected]>

In the future, though, please do keep a more complete intro that you always send with patch resends - because not everyone will know the history - and a detailed changelog - since some people do.

thanks,
-serge

Quoted 130 lines

---
 drivers/char/tpm/tpm.c |   35 ++++++++++++++++++-----------------
 drivers/char/tpm/tpm.h |    2 +-
 2 files changed, 19 insertions(+), 18 deletions(-)

drivers/char/tpm/tpm.c +18 ~~-17~~

index ae766d8..09829f3 100644
@@ -954,13 +954,16 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel);
 
 /*
  * Device file system interface to the TPM
+ *
+ * It's assured that the chip will be opened just once,
+ * by the check of is_open variable, which is protected
+ * by driver_lock.
  */
 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 +978,31 @@ int tpm_open(struct inode *inode, struct file *file)
 		goto err_out;
 	}
 
-	if (chip->num_opens) {
+	if (atomic_read(&chip->is_open)) {
 		dev_dbg(chip->dev, "Another process owns this TPM\n");
 		rc = -EBUSY;
 		goto err_out;
 	}
 
-	chip->num_opens++;
-	get_device(chip->dev);
+	atomic_set(&chip->is_open, 1);
+	get_device(chip->dev); /* protect from chip disappearing */
 
 	spin_unlock(&driver_lock);
 
 	chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL);
 	if (chip->data_buffer == NULL) {
-		chip->num_opens--;
+		atomic_set(&chip->is_open, 0);
 		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 +1016,7 @@ 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_set(&chip->is_open, 0);
 	put_device(chip->dev);
 	kfree(chip->data_buffer);
 	spin_unlock(&driver_lock);

@@ -1082,7 +1082,12 @@ ssize_t tpm_read(struct file *file, char __user *buf,
 	return ret_size;
 }
 EXPORT_SYMBOL_GPL(tpm_read);
-
+/*
+ *   Called on unloading the driver.
+ *
+ *   First part unloading the chip is done here. The remainder
+ *   is done, when the device count reaches 0, in tpm_dev_release().
+ */
 void tpm_remove_hardware(struct device *dev)
 {
 	struct tpm_chip *chip = dev_get_drvdata(dev);

@@ -1231,20 +1236,16 @@ 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;
 }

drivers/char/tpm/tpm.h +1 -1

index e885148..7e0d3fb 100644
@@ -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 is_open;	/* only one allowed */
 	int time_expired;
 
 	/* Data passed to and from the tpm via the read/write calls */

Signature · 1 line

1.5.4.5

Alan Cox

2008-08-26 21:48 UTC #2 lore raw

In reply to Rajiv Andrade

drivers/char/tpm/tpm.c int tpm_open(struct inode *inode, struct file *file) · line 988

Quoted 2 lines

drivers/char/tpm/tpm.c +2 -0

+	atomic_set(&chip->is_open, 1);
+	get_device(chip->dev); /* protect from chip disappearing */

Why not just use test_and_set_bit() ? You seem to be abusing atomic_t to achieve this.

Serge E. Hallyn

2008-08-27 03:20 UTC #3 lore raw

Quoted 5 lines · Alan Cox

drivers/char/tpm/tpm.c int tpm_open(struct inode *inode, struct file *file) · line 988
Quoted 2 lines
drivers/char/tpm/tpm.c +2 -0
+	atomic_set(&chip->is_open, 1);
+	get_device(chip->dev); /* protect from chip disappearing */
Why not just use test_and_set_bit() ? You seem to be abusing atomic_t to achieve this.

Good point. Or heck just make it a simple flag. Earlier I thought there was a place where driver_lock was taken just to do num_opens--, and so replacing the int num_opens with an atomic_t seemed worthwhile. But since is_open is a boolean and now seems to be always protected by driver_lock, a flag seems best.

-serge

Rajiv Andrade

author

2008-08-27 14:37 UTC #4 lore raw

It was all about this section:

Quoted 1 line

      chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8),

GFP_KERNEL);

drivers/char/tpm/tpm.c int tpm_open(struct inode *inode, struct file *file) · line 995

Quoted 4 lines

      if (chip->data_buffer == NULL) {

drivers/char/tpm/tpm.c +1 -1

-             chip->num_opens--;
+             atomic_set(&chip->is_open, 0);
              put_device(chip->dev);

num_opens wasn't protected by driver_lock, so we made num_opens/is_open atomic_t. But an int seems too much for just a flag (as Serge pointed), and the code would be cleaner if we make only this line atomic, by using test_and_set_bit(). Thanks Alan.
I'll rewrite it.

Rajiv

Quoted 19 lines · Serge E. Hallyn

Quoted 5 lines · Alan Cox
drivers/char/tpm/tpm.c int tpm_open(struct inode *inode, struct file *file) · line 988
Quoted 2 lines
drivers/char/tpm/tpm.c +2 -0
+	atomic_set(&chip->is_open, 1);
+	get_device(chip->dev); /* protect from chip disappearing */
Why not just use test_and_set_bit() ? You seem to be abusing atomic_t to achieve this.
Good point. Or heck just make it a simple flag. Earlier I thought there was a place where driver_lock was taken just to do num_opens--, and so replacing the int num_opens with an atomic_t seemed worthwhile. But since is_open is a boolean and now seems to be always protected by driver_lock, a flag seems best.
-serge
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