Commit 7c327d56 authored by Richard Maina's avatar Richard Maina Committed by Bjorn Andersson
Browse files

hwspinlock: Introduce hwspin_lock_bust() 



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: default avatarRichard Maina <quic_rmaina@quicinc.com>
Reviewed-by: default avatarBjorn Andersson <andersson@kernel.org>
Signed-off-by: default avatarChris Lew <quic_clew@quicinc.com>
Link: https://lore.kernel.org/r/20240529-hwspinlock-bust-v3-1-c8b924ffa5a2@quicinc.com


Signed-off-by: default avatarBjorn Andersson <andersson@kernel.org>
parent 1613e604

Documentation/locking/hwspinlock.rst

+11 −0
Original line number Diff line number Diff line
@@ -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);

drivers/hwspinlock/hwspinlock_core.c

+28 −0
Original line number Diff line number Diff line
@@ -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.

 *

 * 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

 * @hwlock_spec: hwlock specifier as found in the device tree

drivers/hwspinlock/hwspinlock_internal.h

+3 −0
Original line number Diff line number Diff line
@@ -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);

};

include/linux/hwspinlock.h

+6 −0
Original line number Diff line number Diff line
@@ -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;