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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Mutexes: blocking mutual exclusion locks
*
* started by Ingo Molnar:
*
* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*/
/*
* This is the control structure for tasks blocked on mutex, which resides
* on the blocked task's kernel stack:
*/
struct mutex_waiter {
struct list_head list;
struct task_struct *task;
struct ww_acquire_ctx *ww_ctx;
#ifdef CONFIG_DEBUG_MUTEXES
void *magic;
#endif
};
/*
* @owner: contains: 'struct task_struct *' to the current lock owner,
* NULL means not owned. Since task_struct pointers are aligned at
* at least L1_CACHE_BYTES, we have low bits to store extra state.
*
* Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
* Bit1 indicates unlock needs to hand the lock to the top-waiter
* Bit2 indicates handoff has been done and we're waiting for pickup.
*/
#define MUTEX_FLAG_WAITERS 0x01
#define MUTEX_FLAG_HANDOFF 0x02
#define MUTEX_FLAG_PICKUP 0x04
#define MUTEX_FLAGS 0x07
/*
* Internal helper function; C doesn't allow us to hide it :/
*
* DO NOT USE (outside of mutex & scheduler code).
*/
static inline struct task_struct *__mutex_owner(struct mutex *lock)
{
if (!lock)
return NULL;
return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
}
#ifdef CONFIG_DEBUG_MUTEXES
extern void debug_mutex_lock_common(struct mutex *lock,
struct mutex_waiter *waiter);
extern void debug_mutex_wake_waiter(struct mutex *lock,
struct mutex_waiter *waiter);
extern void debug_mutex_free_waiter(struct mutex_waiter *waiter);
extern void debug_mutex_add_waiter(struct mutex *lock,
struct mutex_waiter *waiter,
struct task_struct *task);
extern void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
struct task_struct *task);
extern void debug_mutex_unlock(struct mutex *lock);
extern void debug_mutex_init(struct mutex *lock, const char *name,
struct lock_class_key *key);
#else /* CONFIG_DEBUG_MUTEXES */
# define debug_mutex_lock_common(lock, waiter) do { } while (0)
# define debug_mutex_wake_waiter(lock, waiter) do { } while (0)
# define debug_mutex_free_waiter(waiter) do { } while (0)
# define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0)
# define debug_mutex_remove_waiter(lock, waiter, ti) do { } while (0)
# define debug_mutex_unlock(lock) do { } while (0)
# define debug_mutex_init(lock, name, key) do { } while (0)
#endif /* !CONFIG_DEBUG_MUTEXES */
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