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Subject[PATCH][resubmit] TPM: update char dev BKL pushdown
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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 <zohar@us.ibm.com>
Signed-off-by: Rajiv Andrade <srajiv@linux.vnet.ibm.com>

---
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




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