Re: [PATCH 1/2] TPM: update char dev BKL pushdown

From: Serge E. Hallyn
Date: Tue Sep 02 2008 - 11:03:45 EST


Quoting Rajiv Andrade (srajiv@xxxxxxxxxxxxxxxxxx):
> 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. In addition, renames num_open to
> is_open, as only one process can open the file at a time.
>
> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Rajiv Andrade <srajiv@xxxxxxxxxxxxxxxxxx>

Acked-by: Serge Hallyn <serue@xxxxxxxxxx>

> ---
> 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..59b31e1 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 (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);
> + 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--;
> + 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--;
> + 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..2756cab 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 */
> + unsigned long is_open; /* only one allowed */
> int time_expired;
>
> /* Data passed to and from the tpm via the read/write calls */
> --
> 1.5.6.3
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