1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Mutexes: blocking mutual exclusion locks
4 *
5 * started by Ingo Molnar:
6 *
7 * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
8 */
9#ifndef CONFIG_PREEMPT_RT
10/*
11 * This is the control structure for tasks blocked on mutex, which resides
12 * on the blocked task's kernel stack:
13 */
14struct mutex_waiter {
15 struct list_head list;
16 struct task_struct *task;
17 struct ww_acquire_ctx *ww_ctx;
18#ifdef CONFIG_DEBUG_MUTEXES
19 void *magic;
20#endif
21};
22
23/*
24 * @owner: contains: 'struct task_struct *' to the current lock owner,
25 * NULL means not owned. Since task_struct pointers are aligned at
26 * at least L1_CACHE_BYTES, we have low bits to store extra state.
27 *
28 * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
29 * Bit1 indicates unlock needs to hand the lock to the top-waiter
30 * Bit2 indicates handoff has been done and we're waiting for pickup.
31 */
32#define MUTEX_FLAG_WAITERS 0x01
33#define MUTEX_FLAG_HANDOFF 0x02
34#define MUTEX_FLAG_PICKUP 0x04
35
36#define MUTEX_FLAGS 0x07
37
38/*
39 * Internal helper function; C doesn't allow us to hide it :/
40 *
41 * DO NOT USE (outside of mutex & scheduler code).
42 */
43static inline struct task_struct *__mutex_owner(struct mutex *lock)
44{
45 if (!lock)
46 return NULL;
47 return (struct task_struct *)(atomic_long_read(v: &lock->owner) & ~MUTEX_FLAGS);
48}
49
50#ifdef CONFIG_DEBUG_MUTEXES
51extern void debug_mutex_lock_common(struct mutex *lock,
52 struct mutex_waiter *waiter);
53extern void debug_mutex_wake_waiter(struct mutex *lock,
54 struct mutex_waiter *waiter);
55extern void debug_mutex_free_waiter(struct mutex_waiter *waiter);
56extern void debug_mutex_add_waiter(struct mutex *lock,
57 struct mutex_waiter *waiter,
58 struct task_struct *task);
59extern void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
60 struct task_struct *task);
61extern void debug_mutex_unlock(struct mutex *lock);
62extern void debug_mutex_init(struct mutex *lock);
63#else /* CONFIG_DEBUG_MUTEXES */
64# define debug_mutex_lock_common(lock, waiter) do { } while (0)
65# define debug_mutex_wake_waiter(lock, waiter) do { } while (0)
66# define debug_mutex_free_waiter(waiter) do { } while (0)
67# define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0)
68# define debug_mutex_remove_waiter(lock, waiter, ti) do { } while (0)
69# define debug_mutex_unlock(lock) do { } while (0)
70# define debug_mutex_init(lock) do { } while (0)
71#endif /* !CONFIG_DEBUG_MUTEXES */
72#endif /* CONFIG_PREEMPT_RT */
73

source code of linux/kernel/locking/mutex.h