locking: Move the mutex code to kernel/locking/

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-1ditvncg30dgbpvrz2bxfmke@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

5 files changed, 1182 insertions, 0 deletions

diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
new file mode 100644
index 000000000000..fe8bd58b22f8
--- /dev/null
+++ b/kernel/locking/Makefile
@@ -0,0 +1,9 @@
+
+obj-y += mutex.o
+
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_mutex-debug.o = -pg
+CFLAGS_REMOVE_rtmutex-debug.o = -pg
+endif
+
+obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o
diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
new file mode 100644
index 000000000000..7e3443fe1f48
--- /dev/null
+++ b/kernel/locking/mutex-debug.c
@@ -0,0 +1,110 @@
+/*
+ * kernel/mutex-debug.c
+ *
+ * Debugging code for mutexes
+ *
+ * Started by Ingo Molnar:
+ *
+ *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * lock debugging, locking tree, deadlock detection started by:
+ *
+ *  Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey
+ *  Released under the General Public License (GPL).
+ */
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/export.h>
+#include <linux/poison.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/kallsyms.h>
+#include <linux/interrupt.h>
+#include <linux/debug_locks.h>
+
+#include "mutex-debug.h"
+
+/*
+ * Must be called with lock->wait_lock held.
+ */
+void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)
+{
+        memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter));
+        waiter->magic = waiter;
+        INIT_LIST_HEAD(&waiter->list);
+}
+
+void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter)
+{
+        SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock));
+        DEBUG_LOCKS_WARN_ON(list_empty(&lock->wait_list));
+        DEBUG_LOCKS_WARN_ON(waiter->magic != waiter);
+        DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list));
+}
+
+void debug_mutex_free_waiter(struct mutex_waiter *waiter)
+{
+        DEBUG_LOCKS_WARN_ON(!list_empty(&waiter->list));
+        memset(waiter, MUTEX_DEBUG_FREE, sizeof(*waiter));
+}
+
+void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+                            struct thread_info *ti)
+{
+        SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock));
+
+        /* Mark the current thread as blocked on the lock: */
+        ti->task->blocked_on = waiter;
+}
+
+void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+                         struct thread_info *ti)
+{
+        DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list));
+        DEBUG_LOCKS_WARN_ON(waiter->task != ti->task);
+        DEBUG_LOCKS_WARN_ON(ti->task->blocked_on != waiter);
+        ti->task->blocked_on = NULL;
+
+        list_del_init(&waiter->list);
+        waiter->task = NULL;
+}
+
+void debug_mutex_unlock(struct mutex *lock)
+{
+        if (unlikely(!debug_locks))
+                return;
+
+        DEBUG_LOCKS_WARN_ON(lock->magic != lock);
+        DEBUG_LOCKS_WARN_ON(lock->owner != current);
+        DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
+        mutex_clear_owner(lock);
+}
+
+void debug_mutex_init(struct mutex *lock, const char *name,
+                      struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+        /*
+         * Make sure we are not reinitializing a held lock:
+         */
+        debug_check_no_locks_freed((void *)lock, sizeof(*lock));
+        lockdep_init_map(&lock->dep_map, name, key, 0);
+#endif
+        lock->magic = lock;
+}
+
+/***
+ * mutex_destroy - mark a mutex unusable
+ * @lock: the mutex to be destroyed
+ *
+ * This function marks the mutex uninitialized, and any subsequent
+ * use of the mutex is forbidden. The mutex must not be locked when
+ * this function is called.
+ */
+void mutex_destroy(struct mutex *lock)
+{
+        DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock));
+        lock->magic = NULL;
+}
+
+EXPORT_SYMBOL_GPL(mutex_destroy);
diff --git a/kernel/locking/mutex-debug.h b/kernel/locking/mutex-debug.h
new file mode 100644
index 000000000000..0799fd3e4cfa
--- /dev/null
+++ b/kernel/locking/mutex-debug.h
@@ -0,0 +1,55 @@
+/*
+ * Mutexes: blocking mutual exclusion locks
+ *
+ * started by Ingo Molnar:
+ *
+ *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * This file contains mutex debugging related internal declarations,
+ * prototypes and inline functions, for the CONFIG_DEBUG_MUTEXES case.
+ * More details are in kernel/mutex-debug.c.
+ */
+
+/*
+ * This must be called with lock->wait_lock held.
+ */
+extern void debug_mutex_lock_common(struct mutex *lock,
+                                    struct mutex_waiter *waiter);
+extern void debug_mutex_wake_waiter(struct mutex *lock,
+                                    struct mutex_waiter *waiter);
+extern void debug_mutex_free_waiter(struct mutex_waiter *waiter);
+extern void debug_mutex_add_waiter(struct mutex *lock,
+                                   struct mutex_waiter *waiter,
+                                   struct thread_info *ti);
+extern void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+                                struct thread_info *ti);
+extern void debug_mutex_unlock(struct mutex *lock);
+extern void debug_mutex_init(struct mutex *lock, const char *name,
+                             struct lock_class_key *key);
+
+static inline void mutex_set_owner(struct mutex *lock)
+{
+        lock->owner = current;
+}
+
+static inline void mutex_clear_owner(struct mutex *lock)
+{
+        lock->owner = NULL;
+}
+
+#define spin_lock_mutex(lock, flags)                    \
+        do {                                            \
+                struct mutex *l = container_of(lock, struct mutex, wait_lock); \
+                                                        \
+                DEBUG_LOCKS_WARN_ON(in_interrupt());    \
+                local_irq_save(flags);                  \
+                arch_spin_lock(&(lock)->rlock.raw_lock);\
+                DEBUG_LOCKS_WARN_ON(l->magic != l);     \
+        } while (0)
+
+#define spin_unlock_mutex(lock, flags)                          \
+        do {                                                    \
+                arch_spin_unlock(&(lock)->rlock.raw_lock);      \
+                local_irq_restore(flags);                       \
+                preempt_check_resched();                        \
+        } while (0)
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
new file mode 100644
index 000000000000..d24105b1b794
--- /dev/null
+++ b/kernel/locking/mutex.c
@@ -0,0 +1,960 @@
+/*
+ * kernel/mutex.c
+ *
+ * Mutexes: blocking mutual exclusion locks
+ *
+ * Started by Ingo Molnar:
+ *
+ *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * Many thanks to Arjan van de Ven, Thomas Gleixner, Steven Rostedt and
+ * David Howells for suggestions and improvements.
+ *
+ *  - Adaptive spinning for mutexes by Peter Zijlstra. (Ported to mainline
+ *    from the -rt tree, where it was originally implemented for rtmutexes
+ *    by Steven Rostedt, based on work by Gregory Haskins, Peter Morreale
+ *    and Sven Dietrich.
+ *
+ * Also see Documentation/mutex-design.txt.
+ */
+#include <linux/mutex.h>
+#include <linux/ww_mutex.h>
+#include <linux/sched.h>
+#include <linux/sched/rt.h>
+#include <linux/export.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/debug_locks.h>
+
+/*
+ * In the DEBUG case we are using the "NULL fastpath" for mutexes,
+ * which forces all calls into the slowpath:
+ */
+#ifdef CONFIG_DEBUG_MUTEXES
+# include "mutex-debug.h"
+# include <asm-generic/mutex-null.h>
+#else
+# include "mutex.h"
+# include <asm/mutex.h>
+#endif
+
+/*
+ * A negative mutex count indicates that waiters are sleeping waiting for the
+ * mutex.
+ */
+#define MUTEX_SHOW_NO_WAITER(mutex)     (atomic_read(&(mutex)->count) >= 0)
+
+void
+__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
+{
+        atomic_set(&lock->count, 1);
+        spin_lock_init(&lock->wait_lock);
+        INIT_LIST_HEAD(&lock->wait_list);
+        mutex_clear_owner(lock);
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
+        lock->spin_mlock = NULL;
+#endif
+
+        debug_mutex_init(lock, name, key);
+}
+
+EXPORT_SYMBOL(__mutex_init);
+
+#ifndef CONFIG_DEBUG_LOCK_ALLOC
+/*
+ * We split the mutex lock/unlock logic into separate fastpath and
+ * slowpath functions, to reduce the register pressure on the fastpath.
+ * We also put the fastpath first in the kernel image, to make sure the
+ * branch is predicted by the CPU as default-untaken.
+ */
+static __used noinline void __sched
+__mutex_lock_slowpath(atomic_t *lock_count);
+
+/**
+ * mutex_lock - acquire the mutex
+ * @lock: the mutex to be acquired
+ *
+ * Lock the mutex exclusively for this task. If the mutex is not
+ * available right now, it will sleep until it can get it.
+ *
+ * The mutex must later on be released by the same task that
+ * acquired it. Recursive locking is not allowed. The task
+ * may not exit without first unlocking the mutex. Also, kernel
+ * memory where the mutex resides mutex must not be freed with
+ * the mutex still locked. The mutex must first be initialized
+ * (or statically defined) before it can be locked. memset()-ing
+ * the mutex to 0 is not allowed.
+ *
+ * ( The CONFIG_DEBUG_MUTEXES .config option turns on debugging
+ *   checks that will enforce the restrictions and will also do
+ *   deadlock debugging. )
+ *
+ * This function is similar to (but not equivalent to) down().
+ */
+void __sched mutex_lock(struct mutex *lock)
+{
+        might_sleep();
+        /*
+         * The locking fastpath is the 1->0 transition from
+         * 'unlocked' into 'locked' state.
+         */
+        __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath);
+        mutex_set_owner(lock);
+}
+
+EXPORT_SYMBOL(mutex_lock);
+#endif
+
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
+/*
+ * In order to avoid a stampede of mutex spinners from acquiring the mutex
+ * more or less simultaneously, the spinners need to acquire a MCS lock
+ * first before spinning on the owner field.
+ *
+ * We don't inline mspin_lock() so that perf can correctly account for the
+ * time spent in this lock function.
+ */
+struct mspin_node {
+        struct mspin_node *next ;
+        int               locked;       /* 1 if lock acquired */
+};
+#define MLOCK(mutex)    ((struct mspin_node **)&((mutex)->spin_mlock))
+
+static noinline
+void mspin_lock(struct mspin_node **lock, struct mspin_node *node)
+{
+        struct mspin_node *prev;
+
+        /* Init node */
+        node->locked = 0;
+        node->next   = NULL;
+
+        prev = xchg(lock, node);
+        if (likely(prev == NULL)) {
+                /* Lock acquired */
+                node->locked = 1;
+                return;
+        }
+        ACCESS_ONCE(prev->next) = node;
+        smp_wmb();
+        /* Wait until the lock holder passes the lock down */
+        while (!ACCESS_ONCE(node->locked))
+                arch_mutex_cpu_relax();
+}
+
+static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node)
+{
+        struct mspin_node *next = ACCESS_ONCE(node->next);
+
+        if (likely(!next)) {
+                /*
+                 * Release the lock by setting it to NULL
+                 */
+                if (cmpxchg(lock, node, NULL) == node)
+                        return;
+                /* Wait until the next pointer is set */
+                while (!(next = ACCESS_ONCE(node->next)))
+                        arch_mutex_cpu_relax();
+        }
+        ACCESS_ONCE(next->locked) = 1;
+        smp_wmb();
+}
+
+/*
+ * Mutex spinning code migrated from kernel/sched/core.c
+ */
+
+static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
+{
+        if (lock->owner != owner)
+                return false;
+
+        /*
+         * Ensure we emit the owner->on_cpu, dereference _after_ checking
+         * lock->owner still matches owner, if that fails, owner might
+         * point to free()d memory, if it still matches, the rcu_read_lock()
+         * ensures the memory stays valid.
+         */
+        barrier();
+
+        return owner->on_cpu;
+}
+
+/*
+ * Look out! "owner" is an entirely speculative pointer
+ * access and not reliable.
+ */
+static noinline
+int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
+{
+        rcu_read_lock();
+        while (owner_running(lock, owner)) {
+                if (need_resched())
+                        break;
+
+                arch_mutex_cpu_relax();
+        }
+        rcu_read_unlock();
+
+        /*
+         * We break out the loop above on need_resched() and when the
+         * owner changed, which is a sign for heavy contention. Return
+         * success only when lock->owner is NULL.
+         */
+        return lock->owner == NULL;
+}
+
+/*
+ * Initial check for entering the mutex spinning loop
+ */
+static inline int mutex_can_spin_on_owner(struct mutex *lock)
+{
+        struct task_struct *owner;
+        int retval = 1;
+
+        rcu_read_lock();
+        owner = ACCESS_ONCE(lock->owner);
+        if (owner)
+                retval = owner->on_cpu;
+        rcu_read_unlock();
+        /*
+         * if lock->owner is not set, the mutex owner may have just acquired
+         * it and not set the owner yet or the mutex has been released.
+         */
+        return retval;
+}
+#endif
+
+static __used noinline void __sched __mutex_unlock_slowpath(atomic_t *lock_count);
+
+/**
+ * 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)
+{
+        /*
+         * The unlocking fastpath is the 0->1 transition from 'locked'
+         * into 'unlocked' state:
+         */
+#ifndef CONFIG_DEBUG_MUTEXES
+        /*
+         * When debugging is enabled we must not clear the owner before time,
+         * the slow path will always be taken, and that clears the owner field
+         * after verifying that it was indeed current.
+         */
+        mutex_clear_owner(lock);
+#endif
+        __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);
+}
+
+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)
+{
+        /*
+         * The unlocking fastpath is the 0->1 transition from 'locked'
+         * into 'unlocked' state:
+         */
+        if (lock->ctx) {
+#ifdef CONFIG_DEBUG_MUTEXES
+                DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
+#endif
+                if (lock->ctx->acquired > 0)
+                        lock->ctx->acquired--;
+                lock->ctx = NULL;
+        }
+
+#ifndef CONFIG_DEBUG_MUTEXES
+        /*
+         * When debugging is enabled we must not clear the owner before time,
+         * the slow path will always be taken, and that clears the owner field
+         * after verifying that it was indeed current.
+         */
+        mutex_clear_owner(&lock->base);
+#endif
+        __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath);
+}
+EXPORT_SYMBOL(ww_mutex_unlock);
+
+static inline int __sched
+__mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
+{
+        struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
+        struct ww_acquire_ctx *hold_ctx = ACCESS_ONCE(ww->ctx);
+
+        if (!hold_ctx)
+                return 0;
+
+        if (unlikely(ctx == hold_ctx))
+                return -EALREADY;
+
+        if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
+            (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
+#ifdef CONFIG_DEBUG_MUTEXES
+                DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
+                ctx->contending_lock = ww;
+#endif
+                return -EDEADLK;
+        }
+
+        return 0;
+}
+
+static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
+                                                   struct ww_acquire_ctx *ww_ctx)
+{
+#ifdef CONFIG_DEBUG_MUTEXES
+        /*
+         * If this WARN_ON triggers, you used ww_mutex_lock to acquire,
+         * but released with a normal mutex_unlock in this call.
+         *
+         * This should never happen, always use ww_mutex_unlock.
+         */
+        DEBUG_LOCKS_WARN_ON(ww->ctx);
+
+        /*
+         * Not quite done after calling ww_acquire_done() ?
+         */
+        DEBUG_LOCKS_WARN_ON(ww_ctx->done_acquire);
+
+        if (ww_ctx->contending_lock) {
+                /*
+                 * After -EDEADLK you tried to
+                 * acquire a different ww_mutex? Bad!
+                 */
+                DEBUG_LOCKS_WARN_ON(ww_ctx->contending_lock != ww);
+
+                /*
+                 * You called ww_mutex_lock after receiving -EDEADLK,
+                 * but 'forgot' to unlock everything else first?
+                 */
+                DEBUG_LOCKS_WARN_ON(ww_ctx->acquired > 0);
+                ww_ctx->contending_lock = NULL;
+        }
+
+        /*
+         * Naughty, using a different class will lead to undefined behavior!
+         */
+        DEBUG_LOCKS_WARN_ON(ww_ctx->ww_class != ww->ww_class);
+#endif
+        ww_ctx->acquired++;
+}
+
+/*
+ * after acquiring lock with fastpath or when we lost out in contested
+ * slowpath, set ctx and wake up any waiters so they can recheck.
+ *
+ * This function is never called when CONFIG_DEBUG_LOCK_ALLOC is set,
+ * as the fastpath and opportunistic spinning are disabled in that case.
+ */
+static __always_inline void
+ww_mutex_set_context_fastpath(struct ww_mutex *lock,
+                               struct ww_acquire_ctx *ctx)
+{
+        unsigned long flags;
+        struct mutex_waiter *cur;
+
+        ww_mutex_lock_acquired(lock, ctx);
+
+        lock->ctx = ctx;
+
+        /*
+         * The lock->ctx update should be visible on all cores before
+         * the atomic read is done, otherwise contended waiters might be
+         * missed. The contended waiters will either see ww_ctx == NULL
+         * and keep spinning, or it will acquire wait_lock, add itself
+         * to waiter list and sleep.
+         */
+        smp_mb(); /* ^^^ */
+
+        /*
+         * Check if lock is contended, if not there is nobody to wake up
+         */
+        if (likely(atomic_read(&lock->base.count) == 0))
+                return;
+
+        /*
+         * Uh oh, we raced in fastpath, wake up everyone in this case,
+         * so they can see the new lock->ctx.
+         */
+        spin_lock_mutex(&lock->base.wait_lock, flags);
+        list_for_each_entry(cur, &lock->base.wait_list, list) {
+                debug_mutex_wake_waiter(&lock->base, cur);
+                wake_up_process(cur->task);
+        }
+        spin_unlock_mutex(&lock->base.wait_lock, flags);
+}
+
+/*
+ * Lock a mutex (possibly interruptible), slowpath:
+ */
+static __always_inline int __sched
+__mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
+                    struct lockdep_map *nest_lock, unsigned long ip,
+                    struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
+{
+        struct task_struct *task = current;
+        struct mutex_waiter waiter;
+        unsigned long flags;
+        int ret;
+
+        preempt_disable();
+        mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
+
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
+        /*
+         * Optimistic spinning.
+         *
+         * We try to spin for acquisition when we find that there are no
+         * pending waiters and the lock owner is currently running on a
+         * (different) CPU.
+         *
+         * The rationale is that if the lock owner is running, it is likely to
+         * release the lock soon.
+         *
+         * Since this needs the lock owner, and this mutex implementation
+         * doesn't track the owner atomically in the lock field, we need to
+         * track it non-atomically.
+         *
+         * We can't do this for DEBUG_MUTEXES because that relies on wait_lock
+         * to serialize everything.
+         *
+         * The mutex spinners are queued up using MCS lock so that only one
+         * spinner can compete for the mutex. However, if mutex spinning isn't
+         * going to happen, there is no point in going through the lock/unlock
+         * overhead.
+         */
+        if (!mutex_can_spin_on_owner(lock))
+                goto slowpath;
+
+        for (;;) {
+                struct task_struct *owner;
+                struct mspin_node  node;
+
+                if (use_ww_ctx && ww_ctx->acquired > 0) {
+                        struct ww_mutex *ww;
+
+                        ww = container_of(lock, struct ww_mutex, base);
+                        /*
+                         * If ww->ctx is set the contents are undefined, only
+                         * by acquiring wait_lock there is a guarantee that
+                         * they are not invalid when reading.
+                         *
+                         * As such, when deadlock detection needs to be
+                         * performed the optimistic spinning cannot be done.
+                         */
+                        if (ACCESS_ONCE(ww->ctx))
+                                goto slowpath;
+                }
+
+                /*
+                 * If there's an owner, wait for it to either
+                 * release the lock or go to sleep.
+                 */
+                mspin_lock(MLOCK(lock), &node);
+                owner = ACCESS_ONCE(lock->owner);
+                if (owner && !mutex_spin_on_owner(lock, owner)) {
+                        mspin_unlock(MLOCK(lock), &node);
+                        goto slowpath;
+                }
+
+                if ((atomic_read(&lock->count) == 1) &&
+                    (atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
+                        lock_acquired(&lock->dep_map, ip);
+                        if (use_ww_ctx) {
+                                struct ww_mutex *ww;
+                                ww = container_of(lock, struct ww_mutex, base);
+
+                                ww_mutex_set_context_fastpath(ww, ww_ctx);
+                        }
+
+                        mutex_set_owner(lock);
+                        mspin_unlock(MLOCK(lock), &node);
+                        preempt_enable();
+                        return 0;
+                }
+                mspin_unlock(MLOCK(lock), &node);
+
+                /*
+                 * When there's no owner, we might have preempted between the
+                 * owner acquiring the lock and setting the owner field. If
+                 * we're an RT task that will live-lock because we won't let
+                 * the owner complete.
+                 */
+                if (!owner && (need_resched() || rt_task(task)))
+                        goto slowpath;
+
+                /*
+                 * The cpu_relax() call is a compiler barrier which forces
+                 * everything in this loop to be re-loaded. We don't need
+                 * memory barriers as we'll eventually observe the right
+                 * values at the cost of a few extra spins.
+                 */
+                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 (use_ww_ctx && 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 (use_ww_ctx) {
+                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, 0);
+}
+
+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, 0);
+}
+
+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, 0);
+}
+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, 0);
+}
+
+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, 1);
+        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, 1);
+
+        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, 0);
+}
+
+static noinline int __sched
+__mutex_lock_killable_slowpath(struct mutex *lock)
+{
+        return __mutex_lock_common(lock, TASK_KILLABLE, 0,
+                                   NULL, _RET_IP_, NULL, 0);
+}
+
+static noinline int __sched
+__mutex_lock_interruptible_slowpath(struct mutex *lock)
+{
+        return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
+                                   NULL, _RET_IP_, NULL, 0);
+}
+
+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, 1);
+}
+
+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, 1);
+}
+
+#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);
diff --git a/kernel/locking/mutex.h b/kernel/locking/mutex.h
new file mode 100644
index 000000000000..4115fbf83b12
--- /dev/null
+++ b/kernel/locking/mutex.h
@@ -0,0 +1,48 @@
+/*
+ * Mutexes: blocking mutual exclusion locks
+ *
+ * started by Ingo Molnar:
+ *
+ *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * This file contains mutex debugging related internal prototypes, for the
+ * !CONFIG_DEBUG_MUTEXES case. Most of them are NOPs:
+ */
+
+#define spin_lock_mutex(lock, flags) \
+                do { spin_lock(lock); (void)(flags); } while (0)
+#define spin_unlock_mutex(lock, flags) \
+                do { spin_unlock(lock); (void)(flags); } while (0)
+#define mutex_remove_waiter(lock, waiter, ti) \
+                __list_del((waiter)->list.prev, (waiter)->list.next)
+
+#ifdef CONFIG_SMP
+static inline void mutex_set_owner(struct mutex *lock)
+{
+        lock->owner = current;
+}
+
+static inline void mutex_clear_owner(struct mutex *lock)
+{
+        lock->owner = NULL;
+}
+#else
+static inline void mutex_set_owner(struct mutex *lock)
+{
+}
+
+static inline void mutex_clear_owner(struct mutex *lock)
+{
+}
+#endif
+
+#define debug_mutex_wake_waiter(lock, waiter)           do { } while (0)
+#define debug_mutex_free_waiter(waiter)                 do { } while (0)
+#define debug_mutex_add_waiter(lock, waiter, ti)        do { } while (0)
+#define debug_mutex_unlock(lock)                        do { } while (0)
+#define debug_mutex_init(lock, name, key)               do { } while (0)
+
+static inline void
+debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)
+{
+}