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Message-Id: <1223303391.6774.39.camel@dyn536739.br.ibm.com>
Date: Mon, 06 Oct 2008 11:29:51 -0300
From: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
To: "Serge E. Hallyn" <serue@...ibm.com>
Cc: linux-kernel@...r.kernel.org, zohar@...ux.vnet.ibm.com,
akpm@...ux-foundation.org, jmorris@...ei.org
Subject: Re: [PATCH 3/5][resubmit][FIXED] TPM: rcu locking
This is a resubmission of rcu locking patch, posted some hours ago, addressing Serge Hallyn's comment.
In the previous patch there was missing the spin_lock/unlock protecting list_add_rcu()
in tpm_register_hardware(). There were also an unnecessary list_del() inside the same function,
that is now being removed.
Signed-off-by: Mimi Zohar <zohar@...ux.vnet.ibm.com>
Signed-off-by: Rajiv Andrade <srajiv@...ux.vnet.ibm.com>
Acked-by: Serge E. Hallyn <serue@...ibm.com>
---
drivers/char/tpm/tpm.c | 61 +++++++++++++++++++-----------------------------
1 files changed, 24 insertions(+), 37 deletions(-)
diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index dfd4e7f..e96ca5a 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -961,33 +961,28 @@ EXPORT_SYMBOL_GPL(tpm_store_cancel);
*/
int tpm_open(struct inode *inode, struct file *file)
{
- int rc = 0, minor = iminor(inode);
+ int minor = iminor(inode);
struct tpm_chip *chip = NULL, *pos;
- spin_lock(&driver_lock);
-
- list_for_each_entry(pos, &tpm_chip_list, list) {
+ rcu_read_lock();
+ list_for_each_entry_rcu(pos, &tpm_chip_list, list) {
if (pos->vendor.miscdev.minor == minor) {
chip = pos;
+ get_device(chip->dev);
break;
}
}
+ rcu_read_unlock();
- if (chip == NULL) {
- rc = -ENODEV;
- goto err_out;
- }
+ if (!chip)
+ return -ENODEV;
if (test_and_set_bit(0, &chip->is_open)) {
dev_dbg(chip->dev, "Another process owns this TPM\n");
- rc = -EBUSY;
- goto err_out;
+ put_device(chip->dev);
+ return -EBUSY;
}
- get_device(chip->dev);
-
- spin_unlock(&driver_lock);
-
chip->data_buffer = kmalloc(TPM_BUFSIZE * sizeof(u8), GFP_KERNEL);
if (chip->data_buffer == NULL) {
clear_bit(0, &chip->is_open);
@@ -999,26 +994,23 @@ int tpm_open(struct inode *inode, struct file *file)
file->private_data = chip;
return 0;
-
-err_out:
- spin_unlock(&driver_lock);
- return rc;
}
EXPORT_SYMBOL_GPL(tpm_open);
+/*
+ * Called on file close
+ */
int tpm_release(struct inode *inode, struct file *file)
{
struct tpm_chip *chip = file->private_data;
flush_scheduled_work();
- spin_lock(&driver_lock);
file->private_data = NULL;
del_singleshot_timer_sync(&chip->user_read_timer);
atomic_set(&chip->data_pending, 0);
+ kfree(chip->data_buffer);
clear_bit(0, &chip->is_open);
put_device(chip->dev);
- kfree(chip->data_buffer);
- spin_unlock(&driver_lock);
return 0;
}
EXPORT_SYMBOL_GPL(tpm_release);
@@ -1092,13 +1084,11 @@ void tpm_remove_hardware(struct device *dev)
}
spin_lock(&driver_lock);
-
- list_del(&chip->list);
-
+ list_del_rcu(&chip->list);
spin_unlock(&driver_lock);
+ synchronize_rcu();
misc_deregister(&chip->vendor.miscdev);
-
sysfs_remove_group(&dev->kobj, chip->vendor.attr_group);
tpm_bios_log_teardown(chip->bios_dir);
@@ -1146,8 +1136,7 @@ EXPORT_SYMBOL_GPL(tpm_pm_resume);
/*
* Once all references to platform device are down to 0,
* release all allocated structures.
- * In case vendor provided release function,
- * call it too.
+ * In case vendor provided release function, call it too.
*/
static void tpm_dev_release(struct device *dev)
{
@@ -1155,7 +1144,6 @@ static void tpm_dev_release(struct device *dev)
if (chip->vendor.release)
chip->vendor.release(dev);
-
chip->release(dev);
clear_bit(chip->dev_num, dev_mask);
@@ -1170,8 +1158,8 @@ static void tpm_dev_release(struct device *dev)
* upon errant exit from this function specific probe function should call
* pci_disable_device
*/
-struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vendor_specific
- *entry)
+struct tpm_chip *tpm_register_hardware(struct device *dev,
+ const struct tpm_vendor_specific *entry)
{
#define DEVNAME_SIZE 7
@@ -1230,21 +1218,20 @@ 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);
+ /* Make chip available */
+ spin_lock(&driver_lock);
+ list_add_rcu(&chip->list, &tpm_chip_list);
+ spin_unlock(&driver_lock);
+
return chip;
}
EXPORT_SYMBOL_GPL(tpm_register_hardware);
--
1.5.6.3
--
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