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 #include <linux/mutex.h>
11 /*
12 * This is the control structure for tasks blocked on mutex, which resides
13 * on the blocked task's kernel stack:
14 */
15 struct mutex_waiter {
16 struct list_head list;
17 struct task_struct *task;
18 struct ww_acquire_ctx *ww_ctx;
19 #ifdef CONFIG_DEBUG_MUTEXES
20 void *magic;
21 #endif
22 };
23
24 /*
25 * @owner: contains: 'struct task_struct *' to the current lock owner,
26 * NULL means not owned. Since task_struct pointers are aligned at
27 * at least L1_CACHE_BYTES, we have low bits to store extra state.
28 *
29 * Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
30 * Bit1 indicates unlock needs to hand the lock to the top-waiter
31 * Bit2 indicates handoff has been done and we're waiting for pickup.
32 */
33 #define MUTEX_FLAG_WAITERS 0x01
34 #define MUTEX_FLAG_HANDOFF 0x02
35 #define MUTEX_FLAG_PICKUP 0x04
36
37 #define MUTEX_FLAGS 0x07
38
39 /*
40 * Internal helper function; C doesn't allow us to hide it :/
41 *
42 * DO NOT USE (outside of mutex & scheduler code).
43 */
__mutex_owner(struct mutex * lock)44 static inline struct task_struct *__mutex_owner(struct mutex *lock)
45 {
46 if (!lock)
47 return NULL;
48 return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
49 }
50
get_task_blocked_on(struct task_struct * p)51 static inline struct mutex *get_task_blocked_on(struct task_struct *p)
52 {
53 guard(raw_spinlock_irqsave)(&p->blocked_lock);
54 return __get_task_blocked_on(p);
55 }
56
57 #ifdef CONFIG_DEBUG_MUTEXES
58 extern void debug_mutex_lock_common(struct mutex *lock,
59 struct mutex_waiter *waiter);
60 extern void debug_mutex_wake_waiter(struct mutex *lock,
61 struct mutex_waiter *waiter);
62 extern void debug_mutex_free_waiter(struct mutex_waiter *waiter);
63 extern void debug_mutex_add_waiter(struct mutex *lock,
64 struct mutex_waiter *waiter,
65 struct task_struct *task);
66 extern void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
67 struct task_struct *task);
68 extern void debug_mutex_unlock(struct mutex *lock);
69 extern void debug_mutex_init(struct mutex *lock);
70 #else /* CONFIG_DEBUG_MUTEXES */
71 # define debug_mutex_lock_common(lock, waiter) do { } while (0)
72 # define debug_mutex_wake_waiter(lock, waiter) do { } while (0)
73 # define debug_mutex_free_waiter(waiter) do { } while (0)
74 # define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0)
75 # define debug_mutex_remove_waiter(lock, waiter, ti) do { } while (0)
76 # define debug_mutex_unlock(lock) do { } while (0)
77 # define debug_mutex_init(lock) do { } while (0)
78 #endif /* !CONFIG_DEBUG_MUTEXES */
79 #endif /* CONFIG_PREEMPT_RT */
80