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![Peter Zijlstra](/assets/img/avatar_default.png)
Have the trace_contention_*() tracepoints consistently include adaptive spinning. In order to differentiate between the spinning and non-spinning states add LCB_F_MUTEX and combine with LCB_F_SPIN. The consequence is that a mutex contention can now triggler multiple _begin() tracepoints before triggering an _end(). Additionally, this fixes one path where mutex would trigger _end() without ever seeing a _begin(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
1151 lines
29 KiB
C
1151 lines
29 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* kernel/locking/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/locking/mutex-design.rst.
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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/signal.h>
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#include <linux/sched/rt.h>
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#include <linux/sched/wake_q.h>
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#include <linux/sched/debug.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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#include <linux/osq_lock.h>
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#define CREATE_TRACE_POINTS
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#include <trace/events/lock.h>
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#ifndef CONFIG_PREEMPT_RT
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#include "mutex.h"
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#ifdef CONFIG_DEBUG_MUTEXES
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# define MUTEX_WARN_ON(cond) DEBUG_LOCKS_WARN_ON(cond)
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#else
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# define MUTEX_WARN_ON(cond)
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#endif
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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_long_set(&lock->owner, 0);
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raw_spin_lock_init(&lock->wait_lock);
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INIT_LIST_HEAD(&lock->wait_list);
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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osq_lock_init(&lock->osq);
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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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/*
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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 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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return (struct task_struct *)(atomic_long_read(&lock->owner) & ~MUTEX_FLAGS);
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}
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static inline struct task_struct *__owner_task(unsigned long owner)
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{
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return (struct task_struct *)(owner & ~MUTEX_FLAGS);
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}
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bool mutex_is_locked(struct mutex *lock)
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{
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return __mutex_owner(lock) != NULL;
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}
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EXPORT_SYMBOL(mutex_is_locked);
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static inline unsigned long __owner_flags(unsigned long owner)
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{
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return owner & MUTEX_FLAGS;
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}
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/*
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* Returns: __mutex_owner(lock) on failure or NULL on success.
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*/
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static inline struct task_struct *__mutex_trylock_common(struct mutex *lock, bool handoff)
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{
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unsigned long owner, curr = (unsigned long)current;
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owner = atomic_long_read(&lock->owner);
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for (;;) { /* must loop, can race against a flag */
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unsigned long flags = __owner_flags(owner);
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unsigned long task = owner & ~MUTEX_FLAGS;
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if (task) {
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if (flags & MUTEX_FLAG_PICKUP) {
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if (task != curr)
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break;
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flags &= ~MUTEX_FLAG_PICKUP;
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} else if (handoff) {
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if (flags & MUTEX_FLAG_HANDOFF)
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break;
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flags |= MUTEX_FLAG_HANDOFF;
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} else {
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break;
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}
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} else {
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MUTEX_WARN_ON(flags & (MUTEX_FLAG_HANDOFF | MUTEX_FLAG_PICKUP));
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task = curr;
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}
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if (atomic_long_try_cmpxchg_acquire(&lock->owner, &owner, task | flags)) {
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if (task == curr)
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return NULL;
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break;
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}
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}
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return __owner_task(owner);
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}
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/*
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* Trylock or set HANDOFF
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*/
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static inline bool __mutex_trylock_or_handoff(struct mutex *lock, bool handoff)
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{
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return !__mutex_trylock_common(lock, handoff);
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}
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/*
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* Actual trylock that will work on any unlocked state.
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*/
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static inline bool __mutex_trylock(struct mutex *lock)
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{
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return !__mutex_trylock_common(lock, false);
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}
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#ifndef CONFIG_DEBUG_LOCK_ALLOC
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/*
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* Lockdep annotations are contained to the slow paths for simplicity.
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* There is nothing that would stop spreading the lockdep annotations outwards
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* except more code.
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*/
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/*
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* Optimistic trylock that only works in the uncontended case. Make sure to
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* follow with a __mutex_trylock() before failing.
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*/
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static __always_inline bool __mutex_trylock_fast(struct mutex *lock)
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{
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unsigned long curr = (unsigned long)current;
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unsigned long zero = 0UL;
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if (atomic_long_try_cmpxchg_acquire(&lock->owner, &zero, curr))
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return true;
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return false;
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}
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static __always_inline bool __mutex_unlock_fast(struct mutex *lock)
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{
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unsigned long curr = (unsigned long)current;
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return atomic_long_try_cmpxchg_release(&lock->owner, &curr, 0UL);
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}
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#endif
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static inline void __mutex_set_flag(struct mutex *lock, unsigned long flag)
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{
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atomic_long_or(flag, &lock->owner);
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}
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static inline void __mutex_clear_flag(struct mutex *lock, unsigned long flag)
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{
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atomic_long_andnot(flag, &lock->owner);
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}
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static inline bool __mutex_waiter_is_first(struct mutex *lock, struct mutex_waiter *waiter)
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{
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return list_first_entry(&lock->wait_list, struct mutex_waiter, list) == waiter;
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}
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/*
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* Add @waiter to a given location in the lock wait_list and set the
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* FLAG_WAITERS flag if it's the first waiter.
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*/
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static void
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__mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
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struct list_head *list)
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{
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debug_mutex_add_waiter(lock, waiter, current);
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list_add_tail(&waiter->list, list);
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if (__mutex_waiter_is_first(lock, waiter))
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__mutex_set_flag(lock, MUTEX_FLAG_WAITERS);
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}
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static void
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__mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter)
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{
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list_del(&waiter->list);
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if (likely(list_empty(&lock->wait_list)))
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__mutex_clear_flag(lock, MUTEX_FLAGS);
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debug_mutex_remove_waiter(lock, waiter, current);
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}
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/*
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* Give up ownership to a specific task, when @task = NULL, this is equivalent
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* to a regular unlock. Sets PICKUP on a handoff, clears HANDOFF, preserves
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* WAITERS. Provides RELEASE semantics like a regular unlock, the
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* __mutex_trylock() provides a matching ACQUIRE semantics for the handoff.
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*/
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static void __mutex_handoff(struct mutex *lock, struct task_struct *task)
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{
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unsigned long owner = atomic_long_read(&lock->owner);
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for (;;) {
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unsigned long new;
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MUTEX_WARN_ON(__owner_task(owner) != current);
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MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP);
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new = (owner & MUTEX_FLAG_WAITERS);
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new |= (unsigned long)task;
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if (task)
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new |= MUTEX_FLAG_PICKUP;
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if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, new))
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break;
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}
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}
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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 void __sched __mutex_lock_slowpath(struct mutex *lock);
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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 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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if (!__mutex_trylock_fast(lock))
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__mutex_lock_slowpath(lock);
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}
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EXPORT_SYMBOL(mutex_lock);
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#endif
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#include "ww_mutex.h"
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#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
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/*
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* Trylock variant that returns the owning task on failure.
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*/
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static inline struct task_struct *__mutex_trylock_or_owner(struct mutex *lock)
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{
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return __mutex_trylock_common(lock, false);
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}
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static inline
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bool ww_mutex_spin_on_owner(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
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struct mutex_waiter *waiter)
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{
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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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* Check this in every inner iteration because we may
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* be racing against another thread's ww_mutex_lock.
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*/
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if (ww_ctx->acquired > 0 && READ_ONCE(ww->ctx))
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return false;
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/*
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* If we aren't on the wait list yet, cancel the spin
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* if there are waiters. We want to avoid stealing the
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* lock from a waiter with an earlier stamp, since the
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* other thread may already own a lock that we also
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* need.
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*/
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if (!waiter && (atomic_long_read(&lock->owner) & MUTEX_FLAG_WAITERS))
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return false;
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/*
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* Similarly, stop spinning if we are no longer the
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* first waiter.
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*/
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if (waiter && !__mutex_waiter_is_first(lock, waiter))
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return false;
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return true;
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}
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/*
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* Look out! "owner" is an entirely speculative pointer access and not
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* reliable.
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*
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* "noinline" so that this function shows up on perf profiles.
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*/
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static noinline
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bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner,
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struct ww_acquire_ctx *ww_ctx, struct mutex_waiter *waiter)
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{
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bool ret = true;
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lockdep_assert_preemption_disabled();
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while (__mutex_owner(lock) == owner) {
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/*
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* Ensure we emit the owner->on_cpu, dereference _after_
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* checking lock->owner still matches owner. And we already
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* disabled preemption which is equal to the RCU read-side
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* crital section in optimistic spinning code. Thus the
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* task_strcut structure won't go away during the spinning
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* period
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*/
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barrier();
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/*
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* Use vcpu_is_preempted to detect lock holder preemption issue.
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*/
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if (!owner_on_cpu(owner) || need_resched()) {
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ret = false;
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break;
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}
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if (ww_ctx && !ww_mutex_spin_on_owner(lock, ww_ctx, waiter)) {
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ret = false;
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break;
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}
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cpu_relax();
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}
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return ret;
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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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lockdep_assert_preemption_disabled();
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if (need_resched())
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return 0;
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/*
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* We already disabled preemption which is equal to the RCU read-side
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* crital section in optimistic spinning code. Thus the task_strcut
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* structure won't go away during the spinning period.
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*/
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owner = __mutex_owner(lock);
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if (owner)
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retval = owner_on_cpu(owner);
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/*
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* If lock->owner is not set, the mutex has been released. Return true
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* such that we'll trylock in the spin path, which is a faster option
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* than the blocking slow path.
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*/
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return retval;
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}
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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 the lock owner
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* is currently running on a (different) CPU and while we don't
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* need to reschedule. The rationale is that if the lock owner is
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* running, it is likely to release the lock soon.
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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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* Returns true when the lock was taken, otherwise false, indicating
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* that we need to jump to the slowpath and sleep.
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*
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* The waiter flag is set to true if the spinner is a waiter in the wait
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* queue. The waiter-spinner will spin on the lock directly and concurrently
|
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* with the spinner at the head of the OSQ, if present, until the owner is
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* changed to itself.
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*/
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static __always_inline bool
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mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
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struct mutex_waiter *waiter)
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{
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if (!waiter) {
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/*
|
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* The purpose of the mutex_can_spin_on_owner() function is
|
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* to eliminate the overhead of osq_lock() and osq_unlock()
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* in case spinning isn't possible. As a waiter-spinner
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* is not going to take OSQ lock anyway, there is no need
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* to call mutex_can_spin_on_owner().
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*/
|
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if (!mutex_can_spin_on_owner(lock))
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goto fail;
|
|
|
|
/*
|
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* In order to avoid a stampede of mutex spinners trying to
|
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* acquire the mutex all at once, the spinners need to take a
|
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* MCS (queued) lock first before spinning on the owner field.
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*/
|
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if (!osq_lock(&lock->osq))
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goto fail;
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}
|
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|
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for (;;) {
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struct task_struct *owner;
|
|
|
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/* Try to acquire the mutex... */
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owner = __mutex_trylock_or_owner(lock);
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if (!owner)
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break;
|
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|
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/*
|
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* 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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if (!mutex_spin_on_owner(lock, owner, ww_ctx, waiter))
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goto fail_unlock;
|
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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
|
|
* 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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*/
|
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cpu_relax();
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}
|
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|
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if (!waiter)
|
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osq_unlock(&lock->osq);
|
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|
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return true;
|
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|
|
|
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fail_unlock:
|
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if (!waiter)
|
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osq_unlock(&lock->osq);
|
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|
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fail:
|
|
/*
|
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* If we fell out of the spin path because of need_resched(),
|
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* reschedule now, before we try-lock the mutex. This avoids getting
|
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* scheduled out right after we obtained the mutex.
|
|
*/
|
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if (need_resched()) {
|
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/*
|
|
* We _should_ have TASK_RUNNING here, but just in case
|
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* we do not, make it so, otherwise we might get stuck.
|
|
*/
|
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__set_current_state(TASK_RUNNING);
|
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schedule_preempt_disabled();
|
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}
|
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|
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return false;
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}
|
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#else
|
|
static __always_inline bool
|
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mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
|
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struct mutex_waiter *waiter)
|
|
{
|
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return false;
|
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}
|
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#endif
|
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|
|
static noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip);
|
|
|
|
/**
|
|
* mutex_unlock - release the mutex
|
|
* @lock: the mutex to be released
|
|
*
|
|
* Unlock a mutex that has been locked by this task previously.
|
|
*
|
|
* This function must not be used in interrupt context. Unlocking
|
|
* of a not locked mutex is not allowed.
|
|
*
|
|
* This function is similar to (but not equivalent to) up().
|
|
*/
|
|
void __sched mutex_unlock(struct mutex *lock)
|
|
{
|
|
#ifndef CONFIG_DEBUG_LOCK_ALLOC
|
|
if (__mutex_unlock_fast(lock))
|
|
return;
|
|
#endif
|
|
__mutex_unlock_slowpath(lock, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL(mutex_unlock);
|
|
|
|
/**
|
|
* ww_mutex_unlock - release the w/w mutex
|
|
* @lock: the mutex to be released
|
|
*
|
|
* Unlock a mutex that has been locked by this task previously with any of the
|
|
* ww_mutex_lock* functions (with or without an acquire context). It is
|
|
* forbidden to release the locks after releasing the acquire context.
|
|
*
|
|
* This function must not be used in interrupt context. Unlocking
|
|
* of a unlocked mutex is not allowed.
|
|
*/
|
|
void __sched ww_mutex_unlock(struct ww_mutex *lock)
|
|
{
|
|
__ww_mutex_unlock(lock);
|
|
mutex_unlock(&lock->base);
|
|
}
|
|
EXPORT_SYMBOL(ww_mutex_unlock);
|
|
|
|
/*
|
|
* Lock a mutex (possibly interruptible), slowpath:
|
|
*/
|
|
static __always_inline int __sched
|
|
__mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclass,
|
|
struct lockdep_map *nest_lock, unsigned long ip,
|
|
struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
|
|
{
|
|
struct mutex_waiter waiter;
|
|
struct ww_mutex *ww;
|
|
int ret;
|
|
|
|
if (!use_ww_ctx)
|
|
ww_ctx = NULL;
|
|
|
|
might_sleep();
|
|
|
|
MUTEX_WARN_ON(lock->magic != lock);
|
|
|
|
ww = container_of(lock, struct ww_mutex, base);
|
|
if (ww_ctx) {
|
|
if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
|
|
return -EALREADY;
|
|
|
|
/*
|
|
* Reset the wounded flag after a kill. No other process can
|
|
* race and wound us here since they can't have a valid owner
|
|
* pointer if we don't have any locks held.
|
|
*/
|
|
if (ww_ctx->acquired == 0)
|
|
ww_ctx->wounded = 0;
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
nest_lock = &ww_ctx->dep_map;
|
|
#endif
|
|
}
|
|
|
|
preempt_disable();
|
|
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
|
|
|
|
trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN);
|
|
if (__mutex_trylock(lock) ||
|
|
mutex_optimistic_spin(lock, ww_ctx, NULL)) {
|
|
/* got the lock, yay! */
|
|
lock_acquired(&lock->dep_map, ip);
|
|
if (ww_ctx)
|
|
ww_mutex_set_context_fastpath(ww, ww_ctx);
|
|
trace_contention_end(lock, 0);
|
|
preempt_enable();
|
|
return 0;
|
|
}
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
/*
|
|
* After waiting to acquire the wait_lock, try again.
|
|
*/
|
|
if (__mutex_trylock(lock)) {
|
|
if (ww_ctx)
|
|
__ww_mutex_check_waiters(lock, ww_ctx);
|
|
|
|
goto skip_wait;
|
|
}
|
|
|
|
debug_mutex_lock_common(lock, &waiter);
|
|
waiter.task = current;
|
|
if (use_ww_ctx)
|
|
waiter.ww_ctx = ww_ctx;
|
|
|
|
lock_contended(&lock->dep_map, ip);
|
|
|
|
if (!use_ww_ctx) {
|
|
/* add waiting tasks to the end of the waitqueue (FIFO): */
|
|
__mutex_add_waiter(lock, &waiter, &lock->wait_list);
|
|
} else {
|
|
/*
|
|
* Add in stamp order, waking up waiters that must kill
|
|
* themselves.
|
|
*/
|
|
ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
|
|
if (ret)
|
|
goto err_early_kill;
|
|
}
|
|
|
|
set_current_state(state);
|
|
trace_contention_begin(lock, LCB_F_MUTEX);
|
|
for (;;) {
|
|
bool first;
|
|
|
|
/*
|
|
* Once we hold wait_lock, we're serialized against
|
|
* mutex_unlock() handing the lock off to us, do a trylock
|
|
* before testing the error conditions to make sure we pick up
|
|
* the handoff.
|
|
*/
|
|
if (__mutex_trylock(lock))
|
|
goto acquired;
|
|
|
|
/*
|
|
* Check for signals and kill conditions while holding
|
|
* wait_lock. This ensures the lock cancellation is ordered
|
|
* against mutex_unlock() and wake-ups do not go missing.
|
|
*/
|
|
if (signal_pending_state(state, current)) {
|
|
ret = -EINTR;
|
|
goto err;
|
|
}
|
|
|
|
if (ww_ctx) {
|
|
ret = __ww_mutex_check_kill(lock, &waiter, ww_ctx);
|
|
if (ret)
|
|
goto err;
|
|
}
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
schedule_preempt_disabled();
|
|
|
|
first = __mutex_waiter_is_first(lock, &waiter);
|
|
|
|
set_current_state(state);
|
|
/*
|
|
* Here we order against unlock; we must either see it change
|
|
* state back to RUNNING and fall through the next schedule(),
|
|
* or we must see its unlock and acquire.
|
|
*/
|
|
if (__mutex_trylock_or_handoff(lock, first))
|
|
break;
|
|
|
|
if (first) {
|
|
trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN);
|
|
if (mutex_optimistic_spin(lock, ww_ctx, &waiter))
|
|
break;
|
|
trace_contention_begin(lock, LCB_F_MUTEX);
|
|
}
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
}
|
|
raw_spin_lock(&lock->wait_lock);
|
|
acquired:
|
|
__set_current_state(TASK_RUNNING);
|
|
|
|
if (ww_ctx) {
|
|
/*
|
|
* Wound-Wait; we stole the lock (!first_waiter), check the
|
|
* waiters as anyone might want to wound us.
|
|
*/
|
|
if (!ww_ctx->is_wait_die &&
|
|
!__mutex_waiter_is_first(lock, &waiter))
|
|
__ww_mutex_check_waiters(lock, ww_ctx);
|
|
}
|
|
|
|
__mutex_remove_waiter(lock, &waiter);
|
|
|
|
debug_mutex_free_waiter(&waiter);
|
|
|
|
skip_wait:
|
|
/* got the lock - cleanup and rejoice! */
|
|
lock_acquired(&lock->dep_map, ip);
|
|
trace_contention_end(lock, 0);
|
|
|
|
if (ww_ctx)
|
|
ww_mutex_lock_acquired(ww, ww_ctx);
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
preempt_enable();
|
|
return 0;
|
|
|
|
err:
|
|
__set_current_state(TASK_RUNNING);
|
|
__mutex_remove_waiter(lock, &waiter);
|
|
err_early_kill:
|
|
trace_contention_end(lock, ret);
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
debug_mutex_free_waiter(&waiter);
|
|
mutex_release(&lock->dep_map, ip);
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
|
|
static int __sched
|
|
__mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass,
|
|
struct lockdep_map *nest_lock, unsigned long ip)
|
|
{
|
|
return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false);
|
|
}
|
|
|
|
static int __sched
|
|
__ww_mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass,
|
|
unsigned long ip, struct ww_acquire_ctx *ww_ctx)
|
|
{
|
|
return __mutex_lock_common(lock, state, subclass, NULL, ip, ww_ctx, true);
|
|
}
|
|
|
|
/**
|
|
* ww_mutex_trylock - tries to acquire the w/w mutex with optional acquire context
|
|
* @ww: mutex to lock
|
|
* @ww_ctx: optional w/w acquire context
|
|
*
|
|
* Trylocks a mutex with the optional acquire context; no deadlock detection is
|
|
* possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise.
|
|
*
|
|
* Unlike ww_mutex_lock, no deadlock handling is performed. However, if a @ctx is
|
|
* specified, -EALREADY handling may happen in calls to ww_mutex_trylock.
|
|
*
|
|
* A mutex acquired with this function must be released with ww_mutex_unlock.
|
|
*/
|
|
int ww_mutex_trylock(struct ww_mutex *ww, struct ww_acquire_ctx *ww_ctx)
|
|
{
|
|
if (!ww_ctx)
|
|
return mutex_trylock(&ww->base);
|
|
|
|
MUTEX_WARN_ON(ww->base.magic != &ww->base);
|
|
|
|
/*
|
|
* Reset the wounded flag after a kill. No other process can
|
|
* race and wound us here, since they can't have a valid owner
|
|
* pointer if we don't have any locks held.
|
|
*/
|
|
if (ww_ctx->acquired == 0)
|
|
ww_ctx->wounded = 0;
|
|
|
|
if (__mutex_trylock(&ww->base)) {
|
|
ww_mutex_set_context_fastpath(ww, ww_ctx);
|
|
mutex_acquire_nest(&ww->base.dep_map, 0, 1, &ww_ctx->dep_map, _RET_IP_);
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(ww_mutex_trylock);
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
void __sched
|
|
mutex_lock_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
__mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(mutex_lock_nested);
|
|
|
|
void __sched
|
|
_mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
|
|
{
|
|
__mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
|
|
|
|
int __sched
|
|
mutex_lock_killable_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
return __mutex_lock(lock, TASK_KILLABLE, subclass, NULL, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
|
|
|
|
int __sched
|
|
mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
return __mutex_lock(lock, TASK_INTERRUPTIBLE, subclass, NULL, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
|
|
|
|
void __sched
|
|
mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
|
|
{
|
|
int token;
|
|
|
|
might_sleep();
|
|
|
|
token = io_schedule_prepare();
|
|
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
|
|
subclass, NULL, _RET_IP_, NULL, 0);
|
|
io_schedule_finish(token);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_io_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 = __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE,
|
|
0, _RET_IP_, ctx);
|
|
if (!ret && ctx && 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 = __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE,
|
|
0, _RET_IP_, ctx);
|
|
|
|
if (!ret && ctx && 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 noinline void __sched __mutex_unlock_slowpath(struct mutex *lock, unsigned long ip)
|
|
{
|
|
struct task_struct *next = NULL;
|
|
DEFINE_WAKE_Q(wake_q);
|
|
unsigned long owner;
|
|
|
|
mutex_release(&lock->dep_map, ip);
|
|
|
|
/*
|
|
* Release the lock before (potentially) taking the spinlock such that
|
|
* other contenders can get on with things ASAP.
|
|
*
|
|
* Except when HANDOFF, in that case we must not clear the owner field,
|
|
* but instead set it to the top waiter.
|
|
*/
|
|
owner = atomic_long_read(&lock->owner);
|
|
for (;;) {
|
|
MUTEX_WARN_ON(__owner_task(owner) != current);
|
|
MUTEX_WARN_ON(owner & MUTEX_FLAG_PICKUP);
|
|
|
|
if (owner & MUTEX_FLAG_HANDOFF)
|
|
break;
|
|
|
|
if (atomic_long_try_cmpxchg_release(&lock->owner, &owner, __owner_flags(owner))) {
|
|
if (owner & MUTEX_FLAG_WAITERS)
|
|
break;
|
|
|
|
return;
|
|
}
|
|
}
|
|
|
|
raw_spin_lock(&lock->wait_lock);
|
|
debug_mutex_unlock(lock);
|
|
if (!list_empty(&lock->wait_list)) {
|
|
/* get the first entry from the wait-list: */
|
|
struct mutex_waiter *waiter =
|
|
list_first_entry(&lock->wait_list,
|
|
struct mutex_waiter, list);
|
|
|
|
next = waiter->task;
|
|
|
|
debug_mutex_wake_waiter(lock, waiter);
|
|
wake_q_add(&wake_q, next);
|
|
}
|
|
|
|
if (owner & MUTEX_FLAG_HANDOFF)
|
|
__mutex_handoff(lock, next);
|
|
|
|
raw_spin_unlock(&lock->wait_lock);
|
|
|
|
wake_up_q(&wake_q);
|
|
}
|
|
|
|
#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 by signals.
|
|
* @lock: The mutex to be acquired.
|
|
*
|
|
* Lock the mutex like mutex_lock(). If a signal is delivered while the
|
|
* process is sleeping, this function will return without acquiring the
|
|
* mutex.
|
|
*
|
|
* Context: Process context.
|
|
* Return: 0 if the lock was successfully acquired or %-EINTR if a
|
|
* signal arrived.
|
|
*/
|
|
int __sched mutex_lock_interruptible(struct mutex *lock)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(lock))
|
|
return 0;
|
|
|
|
return __mutex_lock_interruptible_slowpath(lock);
|
|
}
|
|
|
|
EXPORT_SYMBOL(mutex_lock_interruptible);
|
|
|
|
/**
|
|
* mutex_lock_killable() - Acquire the mutex, interruptible by fatal signals.
|
|
* @lock: The mutex to be acquired.
|
|
*
|
|
* Lock the mutex like mutex_lock(). If a signal which will be fatal to
|
|
* the current process is delivered while the process is sleeping, this
|
|
* function will return without acquiring the mutex.
|
|
*
|
|
* Context: Process context.
|
|
* Return: 0 if the lock was successfully acquired or %-EINTR if a
|
|
* fatal signal arrived.
|
|
*/
|
|
int __sched mutex_lock_killable(struct mutex *lock)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(lock))
|
|
return 0;
|
|
|
|
return __mutex_lock_killable_slowpath(lock);
|
|
}
|
|
EXPORT_SYMBOL(mutex_lock_killable);
|
|
|
|
/**
|
|
* mutex_lock_io() - Acquire the mutex and mark the process as waiting for I/O
|
|
* @lock: The mutex to be acquired.
|
|
*
|
|
* Lock the mutex like mutex_lock(). While the task is waiting for this
|
|
* mutex, it will be accounted as being in the IO wait state by the
|
|
* scheduler.
|
|
*
|
|
* Context: Process context.
|
|
*/
|
|
void __sched mutex_lock_io(struct mutex *lock)
|
|
{
|
|
int token;
|
|
|
|
token = io_schedule_prepare();
|
|
mutex_lock(lock);
|
|
io_schedule_finish(token);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mutex_lock_io);
|
|
|
|
static noinline void __sched
|
|
__mutex_lock_slowpath(struct mutex *lock)
|
|
{
|
|
__mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_killable_slowpath(struct mutex *lock)
|
|
{
|
|
return __mutex_lock(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__mutex_lock_interruptible_slowpath(struct mutex *lock)
|
|
{
|
|
return __mutex_lock(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
return __ww_mutex_lock(&lock->base, TASK_UNINTERRUPTIBLE, 0,
|
|
_RET_IP_, ctx);
|
|
}
|
|
|
|
static noinline int __sched
|
|
__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
|
|
struct ww_acquire_ctx *ctx)
|
|
{
|
|
return __ww_mutex_lock(&lock->base, TASK_INTERRUPTIBLE, 0,
|
|
_RET_IP_, ctx);
|
|
}
|
|
|
|
#endif
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
bool locked;
|
|
|
|
MUTEX_WARN_ON(lock->magic != lock);
|
|
|
|
locked = __mutex_trylock(lock);
|
|
if (locked)
|
|
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
|
|
|
|
return locked;
|
|
}
|
|
EXPORT_SYMBOL(mutex_trylock);
|
|
|
|
#ifndef CONFIG_DEBUG_LOCK_ALLOC
|
|
int __sched
|
|
ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(&lock->base)) {
|
|
if (ctx)
|
|
ww_mutex_set_context_fastpath(lock, ctx);
|
|
return 0;
|
|
}
|
|
|
|
return __ww_mutex_lock_slowpath(lock, ctx);
|
|
}
|
|
EXPORT_SYMBOL(ww_mutex_lock);
|
|
|
|
int __sched
|
|
ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
|
|
{
|
|
might_sleep();
|
|
|
|
if (__mutex_trylock_fast(&lock->base)) {
|
|
if (ctx)
|
|
ww_mutex_set_context_fastpath(lock, ctx);
|
|
return 0;
|
|
}
|
|
|
|
return __ww_mutex_lock_interruptible_slowpath(lock, ctx);
|
|
}
|
|
EXPORT_SYMBOL(ww_mutex_lock_interruptible);
|
|
|
|
#endif /* !CONFIG_DEBUG_LOCK_ALLOC */
|
|
#endif /* !CONFIG_PREEMPT_RT */
|
|
|
|
/**
|
|
* 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);
|