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25500ba7e7
Instead of embedding a list_head in struct mutex, store a pointer to the first waiter. The list of waiters remains a doubly linked list so we can efficiently add to the tail of the list, remove from the front (or middle) of the list. Some of the list manipulation becomes more complicated, but it's a reasonable tradeoff on the slow paths to shrink data structures which embed a mutex like struct file. Some of the debug checks have to be deleted because there's no equivalent to checking them in the new scheme (eg an empty waiter->list now means that it is the only waiter, not that the waiter is no longer on the list). Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20260305195545.3707590-4-willy@infradead.org
109 lines
2.7 KiB
C
109 lines
2.7 KiB
C
/*
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* Debugging code for mutexes
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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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* lock debugging, locking tree, deadlock detection started by:
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*
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* Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey
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* Released under the General Public License (GPL).
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*/
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#include <linux/mutex.h>
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/export.h>
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#include <linux/poison.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include <linux/kallsyms.h>
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#include <linux/interrupt.h>
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#include <linux/debug_locks.h>
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#include "mutex.h"
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/*
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* Must be called with lock->wait_lock held.
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*/
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void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)
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{
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memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter));
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waiter->magic = waiter;
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INIT_LIST_HEAD(&waiter->list);
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waiter->ww_ctx = MUTEX_POISON_WW_CTX;
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}
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void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter)
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{
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lockdep_assert_held(&lock->wait_lock);
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DEBUG_LOCKS_WARN_ON(!lock->first_waiter);
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DEBUG_LOCKS_WARN_ON(waiter->magic != waiter);
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}
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void debug_mutex_free_waiter(struct mutex_waiter *waiter)
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{
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DEBUG_LOCKS_WARN_ON(!list_empty(&waiter->list));
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memset(waiter, MUTEX_DEBUG_FREE, sizeof(*waiter));
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}
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void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
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struct task_struct *task)
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{
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lockdep_assert_held(&lock->wait_lock);
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/* Current thread can't be already blocked (since it's executing!) */
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DEBUG_LOCKS_WARN_ON(__get_task_blocked_on(task));
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}
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void debug_mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
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struct task_struct *task)
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{
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struct mutex *blocked_on = __get_task_blocked_on(task);
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DEBUG_LOCKS_WARN_ON(waiter->task != task);
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DEBUG_LOCKS_WARN_ON(blocked_on && blocked_on != lock);
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INIT_LIST_HEAD(&waiter->list);
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waiter->task = NULL;
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}
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void debug_mutex_unlock(struct mutex *lock)
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{
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if (likely(debug_locks)) {
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DEBUG_LOCKS_WARN_ON(lock->magic != lock);
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}
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}
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void debug_mutex_init(struct mutex *lock)
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{
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lock->magic = lock;
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}
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static void devm_mutex_release(void *res)
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{
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mutex_destroy(res);
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}
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int __devm_mutex_init(struct device *dev, struct mutex *lock)
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{
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return devm_add_action_or_reset(dev, devm_mutex_release, lock);
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}
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EXPORT_SYMBOL_GPL(__devm_mutex_init);
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/***
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* mutex_destroy - mark a mutex unusable
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* @lock: the mutex to be destroyed
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*
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* This function marks the mutex uninitialized, and any subsequent
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* use of the mutex is forbidden. The mutex must not be locked when
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* this function is called.
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*/
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void mutex_destroy(struct mutex *lock)
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{
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DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock));
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lock->magic = NULL;
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}
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EXPORT_SYMBOL_GPL(mutex_destroy);
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