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![Linus Torvalds](/assets/img/avatar_default.png)
Pull core/locking changes from Ingo Molnar: "Main changes: - another mutex optimization, from Davidlohr Bueso - improved lglock lockdep tracking, from Michel Lespinasse - [ assorted smaller updates, improvements, cleanups. ]" * 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: generic-ipi/locking: Fix misleading smp_call_function_any() description hung_task debugging: Print more info when reporting the problem mutex: Avoid label warning when !CONFIG_MUTEX_SPIN_ON_OWNER mutex: Do not unnecessarily deal with waiters mutex: Fix/document access-once assumption in mutex_can_spin_on_owner() lglock: Update lockdep annotations to report recursive local locks lockdep: Introduce lock_acquire_exclusive()/shared() helper macros
960 lines
25 KiB
C
960 lines
25 KiB
C
/*
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* kernel/mutex.c
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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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* Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
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* David Howells for suggestions and improvements.
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*
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* - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
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* from the -rt tree, where it was originally implemented for rtmutexes
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* by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
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* and Sven Dietrich.
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*
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* Also see Documentation/mutex-design.txt.
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*/
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#include <linux/mutex.h>
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#include <linux/ww_mutex.h>
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#include <linux/sched.h>
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#include <linux/sched/rt.h>
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#include <linux/export.h>
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#include <linux/spinlock.h>
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#include <linux/interrupt.h>
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#include <linux/debug_locks.h>
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/*
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* In the DEBUG case we are using the "NULL fastpath" for mutexes,
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* which forces all calls into the slowpath:
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*/
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#ifdef CONFIG_DEBUG_MUTEXES
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# include "mutex-debug.h"
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# include <asm-generic/mutex-null.h>
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#else
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# include "mutex.h"
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# include <asm/mutex.h>
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#endif
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/*
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* A negative mutex count indicates that waiters are sleeping waiting for the
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* mutex.
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*/
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#define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0)
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void
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__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
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{
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atomic_set(&lock->count, 1);
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spin_lock_init(&lock->wait_lock);
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INIT_LIST_HEAD(&lock->wait_list);
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mutex_clear_owner(lock);
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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lock->spin_mlock = NULL;
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#endif
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debug_mutex_init(lock, name, key);
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}
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EXPORT_SYMBOL(__mutex_init);
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#ifndef CONFIG_DEBUG_LOCK_ALLOC
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/*
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* We split the mutex lock/unlock logic into separate fastpath and
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* slowpath functions, to reduce the register pressure on the fastpath.
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* We also put the fastpath first in the kernel image, to make sure the
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* branch is predicted by the CPU as default-untaken.
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*/
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static __used noinline void __sched
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__mutex_lock_slowpath(atomic_t *lock_count);
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/**
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* mutex_lock - acquire the mutex
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* @lock: the mutex to be acquired
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*
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* Lock the mutex exclusively for this task. If the mutex is not
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* available right now, it will sleep until it can get it.
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*
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* The mutex must later on be released by the same task that
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* acquired it. Recursive locking is not allowed. The task
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* may not exit without first unlocking the mutex. Also, kernel
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* memory where the mutex resides mutex must not be freed with
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* the mutex still locked. The mutex must first be initialized
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* (or statically defined) before it can be locked. memset()-ing
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* the mutex to 0 is not allowed.
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*
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* ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging
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* checks that will enforce the restrictions and will also do
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* deadlock debugging. )
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*
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* This function is similar to (but not equivalent to) down().
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*/
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void __sched mutex_lock(struct mutex *lock)
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{
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might_sleep();
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/*
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* The locking fastpath is the 1->0 transition from
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* 'unlocked' into 'locked' state.
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*/
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__mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath);
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mutex_set_owner(lock);
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}
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EXPORT_SYMBOL(mutex_lock);
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#endif
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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/*
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* In order to avoid a stampede of mutex spinners from acquiring the mutex
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* more or less simultaneously, the spinners need to acquire a MCS lock
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* first before spinning on the owner field.
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*
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* We don't inline mspin_lock() so that perf can correctly account for the
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* time spent in this lock function.
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*/
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struct mspin_node {
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struct mspin_node *next ;
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int locked; /* 1 if lock acquired */
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};
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#define MLOCK(mutex) ((struct mspin_node **)&((mutex)->spin_mlock))
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static noinline
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void mspin_lock(struct mspin_node **lock, struct mspin_node *node)
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{
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struct mspin_node *prev;
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/* Init node */
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node->locked = 0;
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node->next = NULL;
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prev = xchg(lock, node);
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if (likely(prev == NULL)) {
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/* Lock acquired */
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node->locked = 1;
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return;
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}
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ACCESS_ONCE(prev->next) = node;
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smp_wmb();
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/* Wait until the lock holder passes the lock down */
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while (!ACCESS_ONCE(node->locked))
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arch_mutex_cpu_relax();
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}
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static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node)
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{
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struct mspin_node *next = ACCESS_ONCE(node->next);
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if (likely(!next)) {
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/*
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* Release the lock by setting it to NULL
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*/
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if (cmpxchg(lock, node, NULL) == node)
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return;
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/* Wait until the next pointer is set */
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while (!(next = ACCESS_ONCE(node->next)))
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arch_mutex_cpu_relax();
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}
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ACCESS_ONCE(next->locked) = 1;
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smp_wmb();
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}
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/*
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* Mutex spinning code migrated from kernel/sched/core.c
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*/
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static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
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{
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if (lock->owner != owner)
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return false;
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/*
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* Ensure we emit the owner->on_cpu, dereference _after_ checking
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* lock->owner still matches owner, if that fails, owner might
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* point to free()d memory, if it still matches, the rcu_read_lock()
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* ensures the memory stays valid.
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*/
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barrier();
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return owner->on_cpu;
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}
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/*
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* Look out! "owner" is an entirely speculative pointer
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* access and not reliable.
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*/
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static noinline
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int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
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{
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rcu_read_lock();
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while (owner_running(lock, owner)) {
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if (need_resched())
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break;
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arch_mutex_cpu_relax();
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}
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rcu_read_unlock();
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/*
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* We break out the loop above on need_resched() and when the
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* owner changed, which is a sign for heavy contention. Return
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* success only when lock->owner is NULL.
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*/
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return lock->owner == NULL;
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}
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/*
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* Initial check for entering the mutex spinning loop
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*/
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static inline int mutex_can_spin_on_owner(struct mutex *lock)
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{
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struct task_struct *owner;
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int retval = 1;
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rcu_read_lock();
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owner = ACCESS_ONCE(lock->owner);
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if (owner)
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retval = owner->on_cpu;
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rcu_read_unlock();
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/*
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* if lock->owner is not set, the mutex owner may have just acquired
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* it and not set the owner yet or the mutex has been released.
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*/
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return retval;
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}
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#endif
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static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count);
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/**
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* mutex_unlock - release the mutex
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* @lock: the mutex to be released
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*
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* Unlock a mutex that has been locked by this task previously.
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*
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* This function must not be used in interrupt context. Unlocking
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* of a not locked mutex is not allowed.
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*
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* This function is similar to (but not equivalent to) up().
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*/
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void __sched mutex_unlock(struct mutex *lock)
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{
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/*
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* The unlocking fastpath is the 0->1 transition from 'locked'
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* into 'unlocked' state:
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*/
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#ifndef CONFIG_DEBUG_MUTEXES
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/*
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* When debugging is enabled we must not clear the owner before time,
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* the slow path will always be taken, and that clears the owner field
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* after verifying that it was indeed current.
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*/
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mutex_clear_owner(lock);
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#endif
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__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);
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}
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EXPORT_SYMBOL(mutex_unlock);
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/**
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* ww_mutex_unlock - release the w/w mutex
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* @lock: the mutex to be released
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*
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* Unlock a mutex that has been locked by this task previously with any of the
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* ww_mutex_lock* functions (with or without an acquire context). It is
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* forbidden to release the locks after releasing the acquire context.
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*
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* This function must not be used in interrupt context. Unlocking
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* of a unlocked mutex is not allowed.
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*/
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void __sched ww_mutex_unlock(struct ww_mutex *lock)
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{
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/*
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* The unlocking fastpath is the 0->1 transition from 'locked'
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* into 'unlocked' state:
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*/
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if (lock->ctx) {
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#ifdef CONFIG_DEBUG_MUTEXES
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DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
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#endif
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if (lock->ctx->acquired > 0)
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lock->ctx->acquired--;
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lock->ctx = NULL;
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}
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#ifndef CONFIG_DEBUG_MUTEXES
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/*
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* When debugging is enabled we must not clear the owner before time,
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* the slow path will always be taken, and that clears the owner field
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* after verifying that it was indeed current.
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*/
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mutex_clear_owner(&lock->base);
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#endif
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__mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath);
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}
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EXPORT_SYMBOL(ww_mutex_unlock);
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static inline int __sched
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__mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
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{
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struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
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struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx);
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if (!hold_ctx)
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return 0;
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if (unlikely(ctx == hold_ctx))
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return -EALREADY;
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if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
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(ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
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#ifdef CONFIG_DEBUG_MUTEXES
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DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
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ctx->contending_lock = ww;
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#endif
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return -EDEADLK;
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}
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return 0;
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}
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static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
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struct ww_acquire_ctx *ww_ctx)
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{
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#ifdef CONFIG_DEBUG_MUTEXES
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/*
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* If this WARN_ON triggers, you used ww_mutex_lock to acquire,
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* but released with a normal mutex_unlock in this call.
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*
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* This should never happen, always use ww_mutex_unlock.
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*/
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DEBUG_LOCKS_WARN_ON(ww->ctx);
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/*
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* Not quite done after calling ww_acquire_done() ?
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
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if (ww_ctx->contending_lock) {
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/*
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* After -EDEADLK you tried to
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* acquire a different ww_mutex? Bad!
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
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/*
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* You called ww_mutex_lock after receiving -EDEADLK,
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* but 'forgot' to unlock everything else first?
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
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ww_ctx->contending_lock = NULL;
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}
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/*
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* Naughty, using a different class will lead to undefined behavior!
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*/
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DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
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#endif
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ww_ctx->acquired++;
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}
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/*
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* after acquiring lock with fastpath or when we lost out in contested
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* slowpath, set ctx and wake up any waiters so they can recheck.
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*
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* This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set,
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* as the fastpath and opportunistic spinning are disabled in that case.
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*/
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static __always_inline void
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ww_mutex_set_context_fastpath(struct ww_mutex *lock,
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struct ww_acquire_ctx *ctx)
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{
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unsigned long flags;
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struct mutex_waiter *cur;
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ww_mutex_lock_acquired(lock, ctx);
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lock->ctx = ctx;
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/*
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* The lock->ctx update should be visible on all cores before
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* the atomic read is done, otherwise contended waiters might be
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* missed. The contended waiters will either see ww_ctx == NULL
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* and keep spinning, or it will acquire wait_lock, add itself
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* to waiter list and sleep.
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*/
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smp_mb(); /* ^^^ */
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/*
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* Check if lock is contended, if not there is nobody to wake up
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*/
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if (likely(atomic_read(&lock->base.count) == 0))
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return;
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/*
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* Uh oh, we raced in fastpath, wake up everyone in this case,
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* so they can see the new lock->ctx.
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*/
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spin_lock_mutex(&lock->base.wait_lock, flags);
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list_for_each_entry(cur, &lock->base.wait_list, list) {
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debug_mutex_wake_waiter(&lock->base, cur);
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wake_up_process(cur->task);
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}
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spin_unlock_mutex(&lock->base.wait_lock, flags);
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}
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/*
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* Lock a mutex (possibly interruptible), slowpath:
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*/
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static __always_inline int __sched
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__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
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struct lockdep_map *nest_lock, unsigned long ip,
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struct ww_acquire_ctx *ww_ctx)
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{
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struct task_struct *task = current;
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struct mutex_waiter waiter;
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unsigned long flags;
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int ret;
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preempt_disable();
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mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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/*
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* Optimistic spinning.
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*
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* We try to spin for acquisition when we find that there are no
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* pending waiters and the lock owner is currently running on a
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* (different) CPU.
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*
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* The rationale is that if the lock owner is running, it is likely to
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* release the lock soon.
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*
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* Since this needs the lock owner, and this mutex implementation
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* doesn't track the owner atomically in the lock field, we need to
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* track it non-atomically.
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*
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* We can't do this for DEBUG_MUTEXES because that relies on wait_lock
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* to serialize everything.
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*
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* The mutex spinners are queued up using MCS lock so that only one
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* spinner can compete for the mutex. However, if mutex spinning isn't
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* going to happen, there is no point in going through the lock/unlock
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* overhead.
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*/
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if (!mutex_can_spin_on_owner(lock))
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goto slowpath;
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for (;;) {
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struct task_struct *owner;
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struct mspin_node node;
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if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
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struct ww_mutex *ww;
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ww = container_of(lock, struct ww_mutex, base);
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/*
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* If ww->ctx is set the contents are undefined, only
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* by acquiring wait_lock there is a guarantee that
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* they are not invalid when reading.
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*
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* As such, when deadlock detection needs to be
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* performed the optimistic spinning cannot be done.
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*/
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if (ACCESS_ONCE(ww->ctx))
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goto slowpath;
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}
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/*
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* If there's an owner, wait for it to either
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* release the lock or go to sleep.
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*/
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mspin_lock(MLOCK(lock), &node);
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owner = ACCESS_ONCE(lock->owner);
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if (owner && !mutex_spin_on_owner(lock, owner)) {
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mspin_unlock(MLOCK(lock), &node);
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goto slowpath;
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}
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if ((atomic_read(&lock->count) == 1) &&
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(atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
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lock_acquired(&lock->dep_map, ip);
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if (!__builtin_constant_p(ww_ctx == NULL)) {
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struct ww_mutex *ww;
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ww = container_of(lock, struct ww_mutex, base);
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ww_mutex_set_context_fastpath(ww, ww_ctx);
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}
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mutex_set_owner(lock);
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mspin_unlock(MLOCK(lock), &node);
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preempt_enable();
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return 0;
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}
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mspin_unlock(MLOCK(lock), &node);
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/*
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* When there's no owner, we might have preempted between the
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* owner acquiring the lock and setting the owner field. If
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* we're an RT task that will live-lock because we won't let
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* the owner complete.
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*/
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if (!owner && (need_resched() || rt_task(task)))
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goto slowpath;
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/*
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* The cpu_relax() call is a compiler barrier which forces
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* everything in this loop to be re-loaded. We don't need
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* memory barriers as we'll eventually observe the right
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* values at the cost of a few extra spins.
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*/
|
|
arch_mutex_cpu_relax();
|
|
}
|
|
slowpath:
|
|
#endif
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
|
|
/* once more, can we acquire the lock? */
|
|
if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1))
|
|
goto skip_wait;
|
|
|
|
debug_mutex_lock_common(lock, &waiter);
|
|
debug_mutex_add_waiter(lock, &waiter, task_thread_info(task));
|
|
|
|
/* add waiting tasks to the end of the waitqueue (FIFO): */
|
|
list_add_tail(&waiter.list, &lock->wait_list);
|
|
waiter.task = task;
|
|
|
|
lock_contended(&lock->dep_map, ip);
|
|
|
|
for (;;) {
|
|
/*
|
|
* Lets try to take the lock again - this is needed even if
|
|
* we get here for the first time (shortly after failing to
|
|
* acquire the lock), to make sure that we get a wakeup once
|
|
* it's unlocked. Later on, if we sleep, this is the
|
|
* operation that gives us the lock. We xchg it to -1, so
|
|
* that when we release the lock, we properly wake up the
|
|
* other waiters:
|
|
*/
|
|
if (MUTEX_SHOW_NO_WAITER(lock) &&
|
|
(atomic_xchg(&lock->count, -1) == 1))
|
|
break;
|
|
|
|
/*
|
|
* got a signal? (This code gets eliminated in the
|
|
* TASK_UNINTERRUPTIBLE case.)
|
|
*/
|
|
if (unlikely(signal_pending_state(state, task))) {
|
|
ret = -EINTR;
|
|
goto err;
|
|
}
|
|
|
|
if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
|
|
ret = __mutex_lock_check_stamp(lock, ww_ctx);
|
|
if (ret)
|
|
goto err;
|
|
}
|
|
|
|
__set_task_state(task, state);
|
|
|
|
/* didn't get the lock, go to sleep: */
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
schedule_preempt_disabled();
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
}
|
|
mutex_remove_waiter(lock, &waiter, current_thread_info());
|
|
/* set it to 0 if there are no waiters left: */
|
|
if (likely(list_empty(&lock->wait_list)))
|
|
atomic_set(&lock->count, 0);
|
|
debug_mutex_free_waiter(&waiter);
|
|
|
|
skip_wait:
|
|
/* got the lock - cleanup and rejoice! */
|
|
lock_acquired(&lock->dep_map, ip);
|
|
mutex_set_owner(lock);
|
|
|
|
if (!__builtin_constant_p(ww_ctx == NULL)) {
|
|
struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
|
|
struct mutex_waiter *cur;
|
|
|
|
/*
|
|
* This branch gets optimized out for the common case,
|
|
* and is only important for ww_mutex_lock.
|
|
*/
|
|
ww_mutex_lock_acquired(ww, ww_ctx);
|
|
ww->ctx = ww_ctx;
|
|
|
|
/*
|
|
* Give any possible sleeping processes the chance to wake up,
|
|
* so they can recheck if they have to back off.
|
|
*/
|
|
list_for_each_entry(cur, &lock->wait_list, list) {
|
|
debug_mutex_wake_waiter(lock, cur);
|
|
wake_up_process(cur->task);
|
|
}
|
|
}
|
|
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
preempt_enable();
|
|
return 0;
|
|
|
|
err:
|
|
mutex_remove_waiter(lock, &waiter, task_thread_info(task));
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
debug_mutex_free_waiter(&waiter);
|
|
mutex_release(&lock->dep_map, 1, ip);
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
void __sched
|
|
mutex_lock_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
might_sleep();
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
|
|
subclass, NULL, _RET_IP_, NULL);
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(mutex_lock_nested);
|
|
|
|
void __sched
|
|
_mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
|
|
{
|
|
might_sleep();
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
|
|
0, nest, _RET_IP_, NULL);
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
|
|
|
|
int __sched
|
|
mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
might_sleep();
|
|
return __mutex_lock_common(lock, TASK_KILLABLE,
|
|
subclass, NULL, _RET_IP_, NULL);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
|
|
|
|
int __sched
|
|
mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
might_sleep();
|
|
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
|
|
subclass, NULL, _RET_IP_, NULL);
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
|
|
|
|
static inline int
|
|
ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
|
|
unsigned tmp;
|
|
|
|
if (ctx->deadlock_inject_countdown-- == 0) {
|
|
tmp = ctx->deadlock_inject_interval;
|
|
if (tmp > UINT_MAX/4)
|
|
tmp = UINT_MAX;
|
|
else
|
|
tmp = tmp*2 + tmp + tmp/2;
|
|
|
|
ctx->deadlock_inject_interval = tmp;
|
|
ctx->deadlock_inject_countdown = tmp;
|
|
ctx->contending_lock = lock;
|
|
|
|
ww_mutex_unlock(lock);
|
|
|
|
return -EDEADLK;
|
|
}
|
|
#endif
|
|
|
|
return 0;
|
|
}
|
|
|
|
int __sched
|
|
__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
ret = __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
|
|
0, &ctx->dep_map, _RET_IP_, ctx);
|
|
if (!ret && ctx->acquired > 1)
|
|
return ww_mutex_deadlock_injection(lock, ctx);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__ww_mutex_lock);
|
|
|
|
int __sched
|
|
__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
ret = __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
|
|
0, &ctx->dep_map, _RET_IP_, ctx);
|
|
|
|
if (!ret && ctx->acquired > 1)
|
|
return ww_mutex_deadlock_injection(lock, ctx);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);
|
|
|
|
#endif
|
|
|
|
/*
|
|
* Release the lock, slowpath:
|
|
*/
|
|
static inline void
|
|
__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
|
|
{
|
|
struct mutex *lock = container_of(lock_count, struct mutex, count);
|
|
unsigned long flags;
|
|
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
mutex_release(&lock->dep_map, nested, _RET_IP_);
|
|
debug_mutex_unlock(lock);
|
|
|
|
/*
|
|
* some architectures leave the lock unlocked in the fastpath failure
|
|
* case, others need to leave it locked. In the later case we have to
|
|
* unlock it here
|
|
*/
|
|
if (__mutex_slowpath_needs_to_unlock())
|
|
atomic_set(&lock->count, 1);
|
|
|
|
if (!list_empty(&lock->wait_list)) {
|
|
/* get the first entry from the wait-list: */
|
|
struct mutex_waiter *waiter =
|
|
list_entry(lock->wait_list.next,
|
|
struct mutex_waiter, list);
|
|
|
|
debug_mutex_wake_waiter(lock, waiter);
|
|
|
|
wake_up_process(waiter->task);
|
|
}
|
|
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
}
|
|
|
|
/*
|
|
* Release the lock, slowpath:
|
|
*/
|
|
static __used noinline void
|
|
__mutex_unlock_slowpath(atomic_t *lock_count)
|
|
{
|
|
__mutex_unlock_common_slowpath(lock_count, 1);
|
|
}
|
|
|
|
#ifndef CONFIG_DEBUG_LOCK_ALLOC
|
|
/*
|
|
* Here come the less common (and hence less performance-critical) APIs:
|
|
* mutex_lock_interruptible() and mutex_trylock().
|
|
*/
|
|
static noinline int __sched
|
|
__mutex_lock_killable_slowpath(struct mutex *lock);
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_interruptible_slowpath(struct mutex *lock);
|
|
|
|
/**
|
|
* mutex_lock_interruptible - acquire the mutex, interruptible
|
|
* @lock: the mutex to be acquired
|
|
*
|
|
* Lock the mutex like mutex_lock(), and return 0 if the mutex has
|
|
* been acquired or sleep until the mutex becomes available. If a
|
|
* signal arrives while waiting for the lock then this function
|
|
* returns -EINTR.
|
|
*
|
|
* This function is similar to (but not equivalent to) down_interruptible().
|
|
*/
|
|
int __sched mutex_lock_interruptible(struct mutex *lock)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
ret = __mutex_fastpath_lock_retval(&lock->count);
|
|
if (likely(!ret)) {
|
|
mutex_set_owner(lock);
|
|
return 0;
|
|
} else
|
|
return __mutex_lock_interruptible_slowpath(lock);
|
|
}
|
|
|
|
EXPORT_SYMBOL(mutex_lock_interruptible);
|
|
|
|
int __sched mutex_lock_killable(struct mutex *lock)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
ret = __mutex_fastpath_lock_retval(&lock->count);
|
|
if (likely(!ret)) {
|
|
mutex_set_owner(lock);
|
|
return 0;
|
|
} else
|
|
return __mutex_lock_killable_slowpath(lock);
|
|
}
|
|
EXPORT_SYMBOL(mutex_lock_killable);
|
|
|
|
static __used noinline void __sched
|
|
__mutex_lock_slowpath(atomic_t *lock_count)
|
|
{
|
|
struct mutex *lock = container_of(lock_count, struct mutex, count);
|
|
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, NULL);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_killable_slowpath(struct mutex *lock)
|
|
{
|
|
return __mutex_lock_common(lock, TASK_KILLABLE, 0,
|
|
NULL, _RET_IP_, NULL);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_interruptible_slowpath(struct mutex *lock)
|
|
{
|
|
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, NULL);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, ctx);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
|
|
struct ww_acquire_ctx *ctx)
|
|
{
|
|
return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
|
|
NULL, _RET_IP_, ctx);
|
|
}
|
|
|
|
#endif
|
|
|
|
/*
|
|
* Spinlock based trylock, we take the spinlock and check whether we
|
|
* can get the lock:
|
|
*/
|
|
static inline int __mutex_trylock_slowpath(atomic_t *lock_count)
|
|
{
|
|
struct mutex *lock = container_of(lock_count, struct mutex, count);
|
|
unsigned long flags;
|
|
int prev;
|
|
|
|
spin_lock_mutex(&lock->wait_lock, flags);
|
|
|
|
prev = atomic_xchg(&lock->count, -1);
|
|
if (likely(prev == 1)) {
|
|
mutex_set_owner(lock);
|
|
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
|
|
}
|
|
|
|
/* Set it back to 0 if there are no waiters: */
|
|
if (likely(list_empty(&lock->wait_list)))
|
|
atomic_set(&lock->count, 0);
|
|
|
|
spin_unlock_mutex(&lock->wait_lock, flags);
|
|
|
|
return prev == 1;
|
|
}
|
|
|
|
/**
|
|
* mutex_trylock - try to acquire the mutex, without waiting
|
|
* @lock: the mutex to be acquired
|
|
*
|
|
* Try to acquire the mutex atomically. Returns 1 if the mutex
|
|
* has been acquired successfully, and 0 on contention.
|
|
*
|
|
* NOTE: this function follows the spin_trylock() convention, so
|
|
* it is negated from the down_trylock() return values! Be careful
|
|
* about this when converting semaphore users to mutexes.
|
|
*
|
|
* This function must not be used in interrupt context. The
|
|
* mutex must be released by the same task that acquired it.
|
|
*/
|
|
int __sched mutex_trylock(struct mutex *lock)
|
|
{
|
|
int ret;
|
|
|
|
ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath);
|
|
if (ret)
|
|
mutex_set_owner(lock);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(mutex_trylock);
|
|
|
|
#ifndef CONFIG_DEBUG_LOCK_ALLOC
|
|
int __sched
|
|
__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
|
|
ret = __mutex_fastpath_lock_retval(&lock->base.count);
|
|
|
|
if (likely(!ret)) {
|
|
ww_mutex_set_context_fastpath(lock, ctx);
|
|
mutex_set_owner(&lock->base);
|
|
} else
|
|
ret = __ww_mutex_lock_slowpath(lock, ctx);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(__ww_mutex_lock);
|
|
|
|
int __sched
|
|
__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
int ret;
|
|
|
|
might_sleep();
|
|
|
|
ret = __mutex_fastpath_lock_retval(&lock->base.count);
|
|
|
|
if (likely(!ret)) {
|
|
ww_mutex_set_context_fastpath(lock, ctx);
|
|
mutex_set_owner(&lock->base);
|
|
} else
|
|
ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(__ww_mutex_lock_interruptible);
|
|
|
|
#endif
|
|
|
|
/**
|
|
* atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
|
|
* @cnt: the atomic which we are to dec
|
|
* @lock: the mutex to return holding if we dec to 0
|
|
*
|
|
* return true and hold lock if we dec to 0, return false otherwise
|
|
*/
|
|
int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
|
|
{
|
|
/* dec if we can't possibly hit 0 */
|
|
if (atomic_add_unless(cnt, -1, 1))
|
|
return 0;
|
|
/* we might hit 0, so take the lock */
|
|
mutex_lock(lock);
|
|
if (!atomic_dec_and_test(cnt)) {
|
|
/* when we actually did the dec, we didn't hit 0 */
|
|
mutex_unlock(lock);
|
|
return 0;
|
|
}
|
|
/* we hit 0, and we hold the lock */
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL(atomic_dec_and_mutex_lock);
|