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    Subject[PATCH v4 02/10] locking: introduce devm_mutex_init
    Date
    Using of devm API leads to a certain order of releasing resources.
    So all dependent resources which are not devm-wrapped should be deleted
    with respect to devm-release order. Mutex is one of such objects that
    often is bound to other resources and has no own devm wrapping.
    Since mutex_destroy() actually does nothing in non-debug builds
    frequently calling mutex_destroy() is just ignored which is safe for now
    but wrong formally and can lead to a problem if mutex_destroy() will be
    extended so introduce devm_mutex_init()

    Signed-off-by: George Stark <gnstark@salutedevices.com>
    ---
    include/linux/mutex.h | 23 +++++++++++++++++++++++
    kernel/locking/mutex-debug.c | 22 ++++++++++++++++++++++
    2 files changed, 45 insertions(+)

    diff --git a/include/linux/mutex.h b/include/linux/mutex.h
    index a33aa9eb9fc3..ebd03ff1ef66 100644
    --- a/include/linux/mutex.h
    +++ b/include/linux/mutex.h
    @@ -21,6 +21,8 @@
    #include <linux/debug_locks.h>
    #include <linux/cleanup.h>

    +struct device;
    +
    #ifdef CONFIG_DEBUG_LOCK_ALLOC
    # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
    , .dep_map = { \
    @@ -127,6 +129,20 @@ extern void __mutex_init(struct mutex *lock, const char *name,
    */
    extern bool mutex_is_locked(struct mutex *lock);

    +#ifdef CONFIG_DEBUG_MUTEXES
    +
    +int devm_mutex_init(struct device *dev, struct mutex *lock);
    +
    +#else
    +
    +static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
    +{
    + mutex_init(lock);
    + return 0;
    +}
    +
    +#endif
    +
    #else /* !CONFIG_PREEMPT_RT */
    /*
    * Preempt-RT variant based on rtmutexes.
    @@ -169,6 +185,13 @@ do { \
    \
    __mutex_init((mutex), #mutex, &__key); \
    } while (0)
    +
    +static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
    +{
    + mutex_init(lock);
    + return 0;
    +}
    +
    #endif /* CONFIG_PREEMPT_RT */

    /*
    diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
    index bc8abb8549d2..c9efab1a8026 100644
    --- a/kernel/locking/mutex-debug.c
    +++ b/kernel/locking/mutex-debug.c
    @@ -19,6 +19,7 @@
    #include <linux/kallsyms.h>
    #include <linux/interrupt.h>
    #include <linux/debug_locks.h>
    +#include <linux/device.h>

    #include "mutex.h"

    @@ -104,3 +105,24 @@ void mutex_destroy(struct mutex *lock)
    }

    EXPORT_SYMBOL_GPL(mutex_destroy);
    +
    +static void devm_mutex_release(void *res)
    +{
    + mutex_destroy(res);
    +}
    +
    +/**
    + * devm_mutex_init - Resource-managed mutex initialization
    + * @dev: Device which lifetime mutex is bound to
    + * @lock: Pointer to a mutex
    + *
    + * Initialize mutex which is automatically destroyed when the driver is detached.
    + *
    + * Returns: 0 on success or a negative error code on failure.
    + */
    +int devm_mutex_init(struct device *dev, struct mutex *lock)
    +{
    + mutex_init(lock);
    + return devm_add_action_or_reset(dev, devm_mutex_release, lock);
    +}
    +EXPORT_SYMBOL_GPL(devm_mutex_init);
    --
    2.25.1
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