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(-)
diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index ae766d8..09829f3 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -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;
}
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index e885148..7e0d3fb 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 is_open; /* only one allowed */
int time_expired;
/* Data passed to and from the tpm via the read/write calls */
--
1.5.4.5
Quoting Rajiv Andrade ([email protected]):
> 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
> ---
> drivers/char/tpm/tpm.c | 35 ++++++++++++++++++-----------------
> drivers/char/tpm/tpm.h | 2 +-
> 2 files changed, 19 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> index ae766d8..09829f3 100644
> --- a/drivers/char/tpm/tpm.c
> +++ b/drivers/char/tpm/tpm.c
> @@ -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;
> }
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index e885148..7e0d3fb 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 is_open; /* only one allowed */
> int time_expired;
>
> /* Data passed to and from the tpm via the read/write calls */
> --
> 1.5.4.5
>
>
> + 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.
Quoting Alan Cox ([email protected]):
> > + 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
It was all about this section:
> 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);
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
On Tue, 2008-08-26 at 22:19 -0500, Serge E. Hallyn wrote:
> Quoting Alan Cox ([email protected]):
> > > + 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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