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 10 /* 11 * This is the control structure for tasks blocked on mutex, which resides 12 * on the blocked task's kernel stack: 13 */ 14 struct 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 */ 43 static inline struct task_struct *__mutex_owner(struct mutex *lock) 44 { 45 if (!lock) 46 return NULL; 47 return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS); 48 } 49 50 #ifdef CONFIG_DEBUG_MUTEXES 51 extern void debug_mutex_lock_common(struct mutex *lock, 52 struct mutex_waiter *waiter); 53 extern void debug_mutex_wake_waiter(struct mutex *lock, 54 struct mutex_waiter *waiter); 55 extern void debug_mutex_free_waiter(struct mutex_waiter *waiter); 56 extern void debug_mutex_add_waiter(struct mutex *lock, 57 struct mutex_waiter *waiter, 58 struct task_struct *task); 59 extern void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, 60 struct task_struct *task); 61 extern void debug_mutex_unlock(struct mutex *lock); 62 extern void debug_mutex_init(struct mutex *lock, const char *name, 63 struct lock_class_key *key); 64 #else /* CONFIG_DEBUG_MUTEXES */ 65 # define debug_mutex_lock_common(lock, waiter) do { } while (0) 66 # define debug_mutex_wake_waiter(lock, waiter) do { } while (0) 67 # define debug_mutex_free_waiter(waiter) do { } while (0) 68 # define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0) 69 # define debug_mutex_remove_waiter(lock, waiter, ti) do { } while (0) 70 # define debug_mutex_unlock(lock) do { } while (0) 71 # define debug_mutex_init(lock, name, key) do { } while (0) 72 #endif /* !CONFIG_DEBUG_MUTEXES */ 73