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