[PATCH 3/7] hwspinlock: Introduce hwspin_lock_bust()

Chris Lew
2024-05-16T22:59:46Z

From: Richard Maina <quic_rmaina@quicinc.com>

When a remoteproc crashes or goes down unexpectedly this can result in
a state where locks held by the remoteproc will remain locked possibly
resulting in deadlock. This new API hwspin_lock_bust() allows
hwspinlock implementers to define a bust operation for freeing previously
acquired hwspinlocks after verifying ownership of the acquired lock.

Signed-off-by: Richard Maina <quic_rmaina@quicinc.com>
Signed-off-by: Chris Lew <quic_clew@quicinc.com>
---
Documentation/locking/hwspinlock.rst | 11 +++++++++++
drivers/hwspinlock/hwspinlock_core.c | 30 +++++++++++++++++++++++++++++-
drivers/hwspinlock/hwspinlock_internal.h | 3 +++
include/linux/hwspinlock.h | 6 ++++++
4 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/Documentation/locking/hwspinlock.rst b/Documentation/locking/hwspinlock.rst
index c1c2c827b575..6ee94cc6d3b7 100644
--- a/Documentation/locking/hwspinlock.rst
+++ b/Documentation/locking/hwspinlock.rst
@@ -85,6 +85,17 @@ is already free).

Should be called from a process context (might sleep).

+::
+
+ int hwspin_lock_bust(struct hwspinlock *hwlock, unsigned int id);
+
+After verifying the owner of the hwspinlock, release a previously acquired
+hwspinlock; returns 0 on success, or an appropriate error code on failure
+(e.g. -EOPNOTSUPP if the bust operation is not defined for the specific
+hwspinlock).
+
+Should be called from a process context (might sleep).
+
::

int hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int timeout);
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 73a6dff5cbac..a7851262f36f 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -305,6 +305,34 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
}
EXPORT_SYMBOL_GPL(__hwspin_unlock);

+/**
+ * hwspin_lock_bust() - bust a specific hwspinlock
+ * @hwlock: a previously-acquired hwspinlock which we want to bust
+ * @id: identifier of the remote lock holder, if applicable
+ *
+ * This function will bust a hwspinlock that was previously acquired as
+ * long as the current owner of the lock matches the id given by the caller.
+ *
+ * Should be called from a process context (might sleep).
+ *
+ * Returns: 0 on success, or -EINVAL if the hwspinlock does not exist, or
+ * the bust operation fails, and -EOPNOTSUPP if the bust operation is not
+ * defined for the hwspinlock.
+ */
+int hwspin_lock_bust(struct hwspinlock *hwlock, unsigned int id)
+{
+ if (WARN_ON(!hwlock))
+ return -EINVAL;
+
+ if (!hwlock->bank->ops->bust) {
+ pr_err("bust operation not defined\n");
+ return -EOPNOTSUPP;
+ }
+
+ return hwlock->bank->ops->bust(hwlock, id);
+}
+EXPORT_SYMBOL_GPL(hwspin_lock_bust);
+
/**
* of_hwspin_lock_simple_xlate - translate hwlock_spec to return a lock id
* @hwlock_spec: hwlock specifier as found in the device tree
@@ -610,7 +638,7 @@ EXPORT_SYMBOL_GPL(devm_hwspin_lock_unregister);
* This function should be called from the underlying platform-specific
* implementation, to register a new hwspinlock device instance.
*
- * Should be called from a process context (might sleep)
+ * Context: Process context. GFP_KERNEL allocation.
*
* Returns: %0 on success, or an appropriate error code on failure
*/
diff --git a/drivers/hwspinlock/hwspinlock_internal.h b/drivers/hwspinlock/hwspinlock_internal.h
index 12f230b40693..2202f2c9a62e 100644
--- a/drivers/hwspinlock/hwspinlock_internal.h
+++ b/drivers/hwspinlock/hwspinlock_internal.h
@@ -21,6 +21,8 @@ struct hwspinlock_device;
* @trylock: make a single attempt to take the lock. returns 0 on
* failure and true on success. may _not_ sleep.
* @unlock: release the lock. always succeed. may _not_ sleep.
+ * @bust: optional, platform-specific bust handler, called by hwspinlock
+ * core to bust a specific lock.
* @relax: optional, platform-specific relax handler, called by hwspinlock
* core while spinning on a lock, between two successive
* invocations of @trylock. may _not_ sleep.
@@ -28,6 +30,7 @@ struct hwspinlock_device;
struct hwspinlock_ops {
int (*trylock)(struct hwspinlock *lock);
void (*unlock)(struct hwspinlock *lock);
+ int (*bust)(struct hwspinlock *lock, unsigned int id);
void (*relax)(struct hwspinlock *lock);
};

diff --git a/include/linux/hwspinlock.h b/include/linux/hwspinlock.h
index bfe7c1f1ac6d..f0231dbc4777 100644
--- a/include/linux/hwspinlock.h
+++ b/include/linux/hwspinlock.h
@@ -68,6 +68,7 @@ int __hwspin_lock_timeout(struct hwspinlock *, unsigned int, int,
int __hwspin_trylock(struct hwspinlock *, int, unsigned long *);
void __hwspin_unlock(struct hwspinlock *, int, unsigned long *);
int of_hwspin_lock_get_id_byname(struct device_node *np, const char *name);
+int hwspin_lock_bust(struct hwspinlock *hwlock, unsigned int id);
int devm_hwspin_lock_free(struct device *dev, struct hwspinlock *hwlock);
struct hwspinlock *devm_hwspin_lock_request(struct device *dev);
struct hwspinlock *devm_hwspin_lock_request_specific(struct device *dev,
@@ -127,6 +128,11 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
{
}

+static inline int hwspin_lock_bust(struct hwspinlock *hwlock, unsigned int id)
+{
+ return 0;
+}
+
static inline int of_hwspin_lock_get_id(struct device_node *np, int index)
{
return 0;

--
2.25.1