Add a module owner field to the fpga_manager_ops struct and use it to
take the low-level control module's refcount instead of relying on the
parent device's driver pointer. Low-level control modules should
statically set the owner field to THIS_MODULE. To detect when the owner
module pointer becomes stale, set the mops pointer to null during
fpga_mgr_unregister() (called by the low-level module exit function) and
test it before taking the module's refcount. Use a mutex to avoid a
crash that can happen if __fpga_mgr_get() gets suspended between testing
the mops pointer and taking the low-level refcount and then resumes when
the low-level module has already been freed.
Thanks to Xu Yilun for suggesting the locking pattern.
Other changes: move put_device() from __fpga_mgr_get() to fpga_mgr_get()
and of_fpga_mgr_get() to improve code clarity.
Fixes: 654ba4cc0f3e ("fpga manager: ensure lifetime with of_fpga_mgr_get")
Signed-off-by: Marco Pagani <marpagan@xxxxxxxxxx>
---
drivers/fpga/fpga-mgr.c | 50 ++++++++++++++++++++++++-----------
include/linux/fpga/fpga-mgr.h | 4 +++
2 files changed, 38 insertions(+), 16 deletions(-)
diff --git a/drivers/fpga/fpga-mgr.c b/drivers/fpga/fpga-mgr.c
index 06651389c592..a32b7d40080d 100644
--- a/drivers/fpga/fpga-mgr.c
+++ b/drivers/fpga/fpga-mgr.c
@@ -664,20 +664,20 @@ static struct attribute *fpga_mgr_attrs[] = {
};
ATTRIBUTE_GROUPS(fpga_mgr);
-static struct fpga_manager *__fpga_mgr_get(struct device *dev)
+static struct fpga_manager *__fpga_mgr_get(struct device *mgr_dev)
{
struct fpga_manager *mgr;
- mgr = to_fpga_manager(dev);
+ mgr = to_fpga_manager(mgr_dev);
- if (!try_module_get(dev->parent->driver->owner))
- goto err_dev;
+ mutex_lock(&mgr->mops_mutex);
- return mgr;
+ if (!mgr->mops || !try_module_get(mgr->mops->owner))
+ mgr = ERR_PTR(-ENODEV);
-err_dev:
- put_device(dev);
- return ERR_PTR(-ENODEV);
+ mutex_unlock(&mgr->mops_mutex);
+
+ return mgr;
}
static int fpga_mgr_dev_match(struct device *dev, const void *data)
@@ -693,12 +693,18 @@ static int fpga_mgr_dev_match(struct device *dev, const void *data)
*/
struct fpga_manager *fpga_mgr_get(struct device *dev)
{
- struct device *mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev,
- fpga_mgr_dev_match);
+ struct fpga_manager *mgr;
+ struct device *mgr_dev;
+
+ mgr_dev = class_find_device(&fpga_mgr_class, NULL, dev, fpga_mgr_dev_match);
if (!mgr_dev)
return ERR_PTR(-ENODEV);
- return __fpga_mgr_get(mgr_dev);
+ mgr = __fpga_mgr_get(mgr_dev);
+ if (IS_ERR(mgr))
+ put_device(mgr_dev);
+
+ return mgr;
}
EXPORT_SYMBOL_GPL(fpga_mgr_get);
@@ -711,13 +717,18 @@ EXPORT_SYMBOL_GPL(fpga_mgr_get);
*/
struct fpga_manager *of_fpga_mgr_get(struct device_node *node)
{
- struct device *dev;
+ struct fpga_manager *mgr;
+ struct device *mgr_dev;
- dev = class_find_device_by_of_node(&fpga_mgr_class, node);
- if (!dev)
+ mgr_dev = class_find_device_by_of_node(&fpga_mgr_class, node);
+ if (!mgr_dev)
return ERR_PTR(-ENODEV);
- return __fpga_mgr_get(dev);
+ mgr = __fpga_mgr_get(mgr_dev);
+ if (IS_ERR(mgr))
+ put_device(mgr_dev);
+
+ return mgr;
}
EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
@@ -727,7 +738,7 @@ EXPORT_SYMBOL_GPL(of_fpga_mgr_get);
*/
void fpga_mgr_put(struct fpga_manager *mgr)
{
- module_put(mgr->dev.parent->driver->owner);
+ module_put(mgr->mops->owner);
put_device(&mgr->dev);
}
EXPORT_SYMBOL_GPL(fpga_mgr_put);
@@ -803,6 +814,7 @@ fpga_mgr_register_full(struct device *parent, const struct fpga_manager_info *in
}
mutex_init(&mgr->ref_mutex);
+ mutex_init(&mgr->mops_mutex);
mgr->name = info->name;
mgr->mops = info->mops;
@@ -888,6 +900,12 @@ void fpga_mgr_unregister(struct fpga_manager *mgr)
*/
fpga_mgr_fpga_remove(mgr);
+ mutex_lock(&mgr->mops_mutex);
+
+ mgr->mops = NULL;
+
+ mutex_unlock(&mgr->mops_mutex);
+
device_unregister(&mgr->dev);
}
EXPORT_SYMBOL_GPL(fpga_mgr_unregister);
diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
index 54f63459efd6..b4d9413cb444 100644
--- a/include/linux/fpga/fpga-mgr.h
+++ b/include/linux/fpga/fpga-mgr.h
@@ -162,6 +162,7 @@ struct fpga_manager_info {
* @write_complete: set FPGA to operating state after writing is done
* @fpga_remove: optional: Set FPGA into a specific state during driver remove
* @groups: optional attribute groups.
+ * @owner: owner module containing the ops.
*
* fpga_manager_ops are the low level functions implemented by a specific
* fpga manager driver. The optional ones are tested for NULL before being
@@ -184,6 +185,7 @@ struct fpga_manager_ops {
struct fpga_image_info *info);
void (*fpga_remove)(struct fpga_manager *mgr);
const struct attribute_group **groups;
+ struct module *owner;
};
/* FPGA manager status: Partial/Full Reconfiguration errors */
@@ -201,6 +203,7 @@ struct fpga_manager_ops {
* @state: state of fpga manager
* @compat_id: FPGA manager id for compatibility check.
* @mops: pointer to struct of fpga manager ops
+ * @mops_mutex: protects mops from low-level module removal
* @priv: low level driver private date
*/
struct fpga_manager {
@@ -209,6 +212,7 @@ struct fpga_manager {
struct mutex ref_mutex;
enum fpga_mgr_states state;
struct fpga_compat_id *compat_id;
+ struct mutex mops_mutex;
const struct fpga_manager_ops *mops;
void *priv;
};
--
2.43.0
