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Implementing proxy execution requires that scheduler code be able to identify the current owner of a mutex. Expose __mutex_owner() for this purpose (alone!). Includes a null mutex check, so that users of the function can be simplified. [Removed the EXPORT_SYMBOL] [jstultz: Reworked per Peter's suggestions] Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Connor O'Brien <connoro@google.com> Signed-off-by: John Stultz <jstultz@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Metin Kaya <metin.kaya@arm.com> Reviewed-by: Valentin Schneider <vschneid@redhat.com> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com> Tested-by: Metin Kaya <metin.kaya@arm.com> Link: https://lore.kernel.org/r/20241009235352.1614323-4-jstultz@google.com
72 lines
2.5 KiB
C
72 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Mutexes: blocking mutual exclusion locks
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*
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* started by Ingo Molnar:
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*
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* Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*/
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/*
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* This is the control structure for tasks blocked on mutex, which resides
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* on the blocked task's kernel stack:
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*/
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struct mutex_waiter {
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struct list_head list;
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struct task_struct *task;
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struct ww_acquire_ctx *ww_ctx;
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#ifdef CONFIG_DEBUG_MUTEXES
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void *magic;
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#endif
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};
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/*
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* @owner: contains: 'struct task_struct *' to the current lock owner,
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* NULL means not owned. Since task_struct pointers are aligned at
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* at least L1_CACHE_BYTES, we have low bits to store extra state.
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*
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* Bit0 indicates a non-empty waiter list; unlock must issue a wakeup.
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* Bit1 indicates unlock needs to hand the lock to the top-waiter
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* Bit2 indicates handoff has been done and we're waiting for pickup.
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*/
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#define MUTEX_FLAG_WAITERS 0x01
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#define MUTEX_FLAG_HANDOFF 0x02
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#define MUTEX_FLAG_PICKUP 0x04
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#define MUTEX_FLAGS 0x07
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/*
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* Internal helper function; C doesn't allow us to hide it :/
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*
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* DO NOT USE (outside of mutex & scheduler code).
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*/
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static inline struct task_struct *__mutex_owner(struct mutex *lock)
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{
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if (!lock)
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return NULL;
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return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
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}
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#ifdef CONFIG_DEBUG_MUTEXES
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extern void debug_mutex_lock_common(struct mutex *lock,
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struct mutex_waiter *waiter);
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extern void debug_mutex_wake_waiter(struct mutex *lock,
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struct mutex_waiter *waiter);
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extern void debug_mutex_free_waiter(struct mutex_waiter *waiter);
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extern void debug_mutex_add_waiter(struct mutex *lock,
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struct mutex_waiter *waiter,
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struct task_struct *task);
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extern void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
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struct task_struct *task);
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extern void debug_mutex_unlock(struct mutex *lock);
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extern void debug_mutex_init(struct mutex *lock, const char *name,
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struct lock_class_key *key);
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#else /* CONFIG_DEBUG_MUTEXES */
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# define debug_mutex_lock_common(lock, waiter) do { } while (0)
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# define debug_mutex_wake_waiter(lock, waiter) do { } while (0)
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# define debug_mutex_free_waiter(waiter) do { } while (0)
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# define debug_mutex_add_waiter(lock, waiter, ti) do { } while (0)
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# define debug_mutex_remove_waiter(lock, waiter, ti) do { } while (0)
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# define debug_mutex_unlock(lock) do { } while (0)
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# define debug_mutex_init(lock, name, key) do { } while (0)
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#endif /* !CONFIG_DEBUG_MUTEXES */
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