Re: [PATCH AUTOSEL 5.10 20/38] hwspinlock: Introduce hwspin_lock_bust()

Hi!

From: Richard Maina quic_rmaina@quicinc.com

[ Upstream commit 7c327d56597d8de1680cf24e956b704270d3d84a ]

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.

This adds unused infrastructure to -stable. Please drop.

Best regards, Pavel

+++ 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 fd5f5c5a5244d..425597151dd3e 100644 --- a/drivers/hwspinlock/hwspinlock_core.c +++ b/drivers/hwspinlock/hwspinlock_core.c @@ -302,6 +302,34 @@ 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.
• • Context: Process context.
• • 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
• @bank: the hwspinlock device bank

diff --git a/drivers/hwspinlock/hwspinlock_internal.h b/drivers/hwspinlock/hwspinlock_internal.h index 29892767bb7a0..f298fc0ee5adb 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 bfe7c1f1ac6d1..f0231dbc47771 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;