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

Pavel Machek
2024-08-27T12:25:07Z

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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;

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