[PATCH v7 04/10] tpm: Get rid of module locking

Stefan Berger
2016-03-12T02:52:09Z

Now that the tpm core has strong locking around 'ops' it is possible
to remove a TPM driver, module and all, even while user space still
has things like /dev/tpmX open. For consistency and simplicity, drop
the module locking entirely.

The module lock can be dropped since /dev/tpmX holds the reader lock
on 'ops' while using 'ops' and this prevents the module from un-
registering, which needs the writer lock. Once the module unregistered
the 'ops' cannot be found anymore.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
drivers/char/tpm/tpm-chip.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 5793ea1..6636728 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -57,9 +57,6 @@ int tpm_try_get_ops(struct tpm_chip *chip)
if (!chip->ops)
goto out_lock;

- if (!try_module_get(chip->dev.parent->driver->owner))
- goto out_lock;
-
return 0;
out_lock:
up_read(&chip->ops_sem);
@@ -77,7 +74,6 @@ EXPORT_SYMBOL_GPL(tpm_try_get_ops);
*/
void tpm_put_ops(struct tpm_chip *chip)
{
- module_put(chip->dev.parent->driver->owner);
up_read(&chip->ops_sem);
put_device(&chip->dev);
}
@@ -183,7 +179,7 @@ struct tpm_chip *tpmm_chip_alloc(struct device *dev,
goto out;

cdev_init(&chip->cdev, &tpm_fops);
- chip->cdev.owner = dev->driver->owner;
+ chip->cdev.owner = THIS_MODULE;
chip->cdev.kobj.parent = &chip->dev.kobj;

rc = devm_add_action(dev, (void (*)(void *)) put_device, &chip->dev);
--
2.4.3