new file mode 100644
@@ -0,0 +1,333 @@
+#ifndef __BACKPORT_LINUX_WW_MUTEX_H
+#define __BACKPORT_LINUX_WW_MUTEX_H
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,11,0)
+#include_next <linux/ww_mutex.h>
+#else
+#ifdef CPTCFG_BACKPORT_BUILD_WW_MUTEX
+/*
+ * Wound/Wait Mutexes: blocking mutual exclusion locks with deadlock avoidance
+ *
+ * Original mutex implementation started by Ingo Molnar:
+ *
+ * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * Wound/wait implementation:
+ * Copyright (C) 2013 Canonical Ltd.
+ *
+ * This file contains the main data structure and API definitions.
+ */
+
+#include <linux/mutex.h>
+
+struct ww_class {
+ atomic_long_t stamp;
+ struct lock_class_key acquire_key;
+ struct lock_class_key mutex_key;
+ const char *acquire_name;
+ const char *mutex_name;
+};
+
+struct ww_acquire_ctx {
+ struct task_struct *task;
+ unsigned long stamp;
+ unsigned acquired;
+};
+
+struct ww_mutex {
+ struct mutex base;
+ struct ww_acquire_ctx *ctx;
+};
+
+# define __WW_CLASS_MUTEX_INITIALIZER(lockname, ww_class)
+
+#define __WW_CLASS_INITIALIZER(ww_class) \
+ { .stamp = ATOMIC_LONG_INIT(0) \
+ , .acquire_name = #ww_class "_acquire" \
+ , .mutex_name = #ww_class "_mutex" }
+
+#define __WW_MUTEX_INITIALIZER(lockname, class) \
+ { .base = { \__MUTEX_INITIALIZER(lockname) } \
+ __WW_CLASS_MUTEX_INITIALIZER(lockname, class) }
+
+#define DEFINE_WW_CLASS(classname) \
+ struct ww_class classname = __WW_CLASS_INITIALIZER(classname)
+
+#define DEFINE_WW_MUTEX(mutexname, ww_class) \
+ struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class)
+
+/**
+ * ww_mutex_init - initialize the w/w mutex
+ * @lock: the mutex to be initialized
+ * @ww_class: the w/w class the mutex should belong to
+ *
+ * Initialize the w/w mutex to unlocked state and associate it with the given
+ * class.
+ *
+ * It is not allowed to initialize an already locked mutex.
+ */
+#define ww_mutex_init LINUX_BACKPORT(ww_mutex_init)
+static inline void ww_mutex_init(struct ww_mutex *lock,
+ struct ww_class *ww_class)
+{
+ __mutex_init(&lock->base, ww_class->mutex_name, &ww_class->mutex_key);
+ lock->ctx = NULL;
+}
+
+/**
+ * ww_acquire_init - initialize a w/w acquire context
+ * @ctx: w/w acquire context to initialize
+ * @ww_class: w/w class of the context
+ *
+ * Initializes an context to acquire multiple mutexes of the given w/w class.
+ *
+ * Context-based w/w mutex acquiring can be done in any order whatsoever within
+ * a given lock class. Deadlocks will be detected and handled with the
+ * wait/wound logic.
+ *
+ * Mixing of context-based w/w mutex acquiring and single w/w mutex locking can
+ * result in undetected deadlocks and is so forbidden. Mixing different contexts
+ * for the same w/w class when acquiring mutexes can also result in undetected
+ * deadlocks, and is hence also forbidden. Both types of abuse will be caught by
+ * enabling CONFIG_PROVE_LOCKING.
+ *
+ * Nesting of acquire contexts for _different_ w/w classes is possible, subject
+ * to the usual locking rules between different lock classes.
+ *
+ * An acquire context must be released with ww_acquire_fini by the same task
+ * before the memory is freed. It is recommended to allocate the context itself
+ * on the stack.
+ */
+#define ww_acquire_init LINUX_BACKPORT(ww_acquire_init)
+static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
+ struct ww_class *ww_class)
+{
+ ctx->task = current;
+ ctx->stamp = atomic_long_inc_return(&ww_class->stamp);
+ ctx->acquired = 0;
+}
+
+/**
+ * ww_acquire_done - marks the end of the acquire phase
+ * @ctx: the acquire context
+ *
+ * Marks the end of the acquire phase, any further w/w mutex lock calls using
+ * this context are forbidden.
+ *
+ * Calling this function is optional, it is just useful to document w/w mutex
+ * code and clearly designated the acquire phase from actually using the locked
+ * data structures.
+ */
+#define ww_acquire_done LINUX_BACKPORT(ww_acquire_done)
+static inline void ww_acquire_done(struct ww_acquire_ctx *ctx)
+{
+}
+
+/**
+ * ww_acquire_fini - releases a w/w acquire context
+ * @ctx: the acquire context to free
+ *
+ * Releases a w/w acquire context. This must be called _after_ all acquired w/w
+ * mutexes have been released with ww_mutex_unlock.
+ */
+#define ww_acquire_fini LINUX_BACKPORT(ww_acquire_fini)
+static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx)
+{
+}
+
+#define __ww_mutex_lock LINUX_BACKPORT(__ww_mutex_lock)
+extern int __must_check __ww_mutex_lock(struct ww_mutex *lock,
+ struct ww_acquire_ctx *ctx);
+#define __ww_mutex_lock_interruptible LINUX_BACKPORT(__ww_mutex_lock_interruptible)
+extern int __must_check __ww_mutex_lock_interruptible(struct ww_mutex *lock,
+ struct ww_acquire_ctx *ctx);
+
+/**
+ * ww_mutex_lock - acquire the w/w mutex
+ * @lock: the mutex to be acquired
+ * @ctx: w/w acquire context, or NULL to acquire only a single lock.
+ *
+ * Lock the w/w mutex exclusively for this task.
+ *
+ * Deadlocks within a given w/w class of locks are detected and handled with the
+ * wait/wound algorithm. If the lock isn't immediately avaiable this function
+ * will either sleep until it is (wait case). Or it selects the current context
+ * for backing off by returning -EDEADLK (wound case). Trying to acquire the
+ * same lock with the same context twice is also detected and signalled by
+ * returning -EALREADY. Returns 0 if the mutex was successfully acquired.
+ *
+ * In the wound case the caller must release all currently held w/w mutexes for
+ * the given context and then wait for this contending lock to be available by
+ * calling ww_mutex_lock_slow. Alternatively callers can opt to not acquire this
+ * lock and proceed with trying to acquire further w/w mutexes (e.g. when
+ * scanning through lru lists trying to free resources).
+ *
+ * The mutex must later on be released by the same task that
+ * acquired it. The task may not exit without first unlocking the mutex. Also,
+ * kernel memory where the mutex resides 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 mutex must be
+ * of the same w/w lock class as was used to initialize the acquire context.
+ *
+ * A mutex acquired with this function must be released with ww_mutex_unlock.
+ */
+#define ww_mutex_lock LINUX_BACKPORT(ww_mutex_lock)
+static inline int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+ if (ctx)
+ return __ww_mutex_lock(lock, ctx);
+
+ mutex_lock(&lock->base);
+ return 0;
+}
+
+/**
+ * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible
+ * @lock: the mutex to be acquired
+ * @ctx: w/w acquire context
+ *
+ * Lock the w/w mutex exclusively for this task.
+ *
+ * Deadlocks within a given w/w class of locks are detected and handled with the
+ * wait/wound algorithm. If the lock isn't immediately avaiable this function
+ * will either sleep until it is (wait case). Or it selects the current context
+ * for backing off by returning -EDEADLK (wound case). Trying to acquire the
+ * same lock with the same context twice is also detected and signalled by
+ * returning -EALREADY. Returns 0 if the mutex was successfully acquired. If a
+ * signal arrives while waiting for the lock then this function returns -EINTR.
+ *
+ * In the wound case the caller must release all currently held w/w mutexes for
+ * the given context and then wait for this contending lock to be available by
+ * calling ww_mutex_lock_slow_interruptible. Alternatively callers can opt to
+ * not acquire this lock and proceed with trying to acquire further w/w mutexes
+ * (e.g. when scanning through lru lists trying to free resources).
+ *
+ * The mutex must later on be released by the same task that
+ * acquired it. The task may not exit without first unlocking the mutex. Also,
+ * kernel memory where the mutex resides 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 mutex must be
+ * of the same w/w lock class as was used to initialize the acquire context.
+ *
+ * A mutex acquired with this function must be released with ww_mutex_unlock.
+ */
+#define ww_mutex_lock_interruptible LINUX_BACKPORT(ww_mutex_lock_interruptible)
+static inline int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock,
+ struct ww_acquire_ctx *ctx)
+{
+ if (ctx)
+ return __ww_mutex_lock_interruptible(lock, ctx);
+ else
+ return mutex_lock_interruptible(&lock->base);
+}
+
+/**
+ * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex
+ * @lock: the mutex to be acquired
+ * @ctx: w/w acquire context
+ *
+ * Acquires a w/w mutex with the given context after a wound case. This function
+ * will sleep until the lock becomes available.
+ *
+ * The caller must have released all w/w mutexes already acquired with the
+ * context and then call this function on the contended lock.
+ *
+ * Afterwards the caller may continue to (re)acquire the other w/w mutexes it
+ * needs with ww_mutex_lock. Note that the -EALREADY return code from
+ * ww_mutex_lock can be used to avoid locking this contended mutex twice.
+ *
+ * It is forbidden to call this function with any other w/w mutexes associated
+ * with the context held. It is forbidden to call this on anything else than the
+ * contending mutex.
+ *
+ * Note that the slowpath lock acquiring can also be done by calling
+ * ww_mutex_lock directly. This function here is simply to help w/w mutex
+ * locking code readability by clearly denoting the slowpath.
+ */
+#define ww_mutex_lock_slow LINUX_BACKPORT(ww_mutex_lock_slow)
+static inline void
+ww_mutex_lock_slow(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+ int ret;
+ ret = ww_mutex_lock(lock, ctx);
+ (void)ret;
+}
+
+/**
+ * ww_mutex_lock_slow_interruptible - slowpath acquiring of the w/w mutex, interruptible
+ * @lock: the mutex to be acquired
+ * @ctx: w/w acquire context
+ *
+ * Acquires a w/w mutex with the given context after a wound case. This function
+ * will sleep until the lock becomes available and returns 0 when the lock has
+ * been acquired. If a signal arrives while waiting for the lock then this
+ * function returns -EINTR.
+ *
+ * The caller must have released all w/w mutexes already acquired with the
+ * context and then call this function on the contended lock.
+ *
+ * Afterwards the caller may continue to (re)acquire the other w/w mutexes it
+ * needs with ww_mutex_lock. Note that the -EALREADY return code from
+ * ww_mutex_lock can be used to avoid locking this contended mutex twice.
+ *
+ * It is forbidden to call this function with any other w/w mutexes associated
+ * with the given context held. It is forbidden to call this on anything else
+ * than the contending mutex.
+ *
+ * Note that the slowpath lock acquiring can also be done by calling
+ * ww_mutex_lock_interruptible directly. This function here is simply to help
+ * w/w mutex locking code readability by clearly denoting the slowpath.
+ */
+#define ww_mutex_lock_slow_interruptible LINUX_BACKPORT(ww_mutex_lock_slow_interruptible)
+static inline int __must_check
+ww_mutex_lock_slow_interruptible(struct ww_mutex *lock,
+ struct ww_acquire_ctx *ctx)
+{
+ return ww_mutex_lock_interruptible(lock, ctx);
+}
+
+#define ww_mutex_unlock LINUX_BACKPORT(ww_mutex_unlock)
+extern void ww_mutex_unlock(struct ww_mutex *lock);
+
+/**
+ * ww_mutex_trylock - tries to acquire the w/w mutex without acquire context
+ * @lock: mutex to lock
+ *
+ * Trylocks a mutex without acquire context, so no deadlock detection is
+ * possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise.
+ */
+#define ww_mutex_trylock LINUX_BACKPORT(ww_mutex_trylock)
+static inline int __must_check ww_mutex_trylock(struct ww_mutex *lock)
+{
+ return mutex_trylock(&lock->base);
+}
+
+/***
+ * ww_mutex_destroy - mark a w/w 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.
+ */
+#define ww_mutex_destroy LINUX_BACKPORT(ww_mutex_destroy)
+static inline void ww_mutex_destroy(struct ww_mutex *lock)
+{
+ mutex_destroy(&lock->base);
+}
+
+/**
+ * ww_mutex_is_locked - is the w/w mutex locked
+ * @lock: the mutex to be queried
+ *
+ * Returns 1 if the mutex is locked, 0 if unlocked.
+ */
+#define ww_mutex_is_locked LINUX_BACKPORT(ww_mutex_is_locked)
+static inline bool ww_mutex_is_locked(struct ww_mutex *lock)
+{
+ return mutex_is_locked(&lock->base);
+}
+
+#endif /* CPTCFG_BACKPORT_BUILD_WW_MUTEX */
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3,11,0) */
+#endif /* __BACKPORT_LINUX_WW_MUTEX_H */
@@ -185,6 +185,17 @@ config BACKPORT_LEDS_CLASS
config BACKPORT_LEDS_TRIGGERS
bool
+config BACKPORT_BUILD_WW_MUTEX
+ bool
+ # Build only if on kernels < 3.11
+ # For now only DRM drivers use ww mutexes.
+ depends on DRM && BACKPORT_KERNEL_3_11
+ default y if BACKPORT_USERSEL_BUILD_ALL
+ # probably a bad idea if you have these options given we
+ # ripped those options out.
+ depends on !DEBUG_MUTEXES
+ depends on !DEBUG_LOCK_ALLOC
+
config BACKPORT_BUILD_RADIX_HELPERS
bool
# You have selected to build backported DRM drivers
@@ -41,3 +41,4 @@ compat-$(CPTCFG_BACKPORT_BUILD_KFIFO) += kfifo.o
compat-$(CPTCFG_BACKPORT_BUILD_GENERIC_ATOMIC64) += compat_atomic.o
compat-$(CPTCFG_BACKPORT_BUILD_DMA_SHARED_HELPERS) += dma-shared-helpers.o
compat-$(CPTCFG_BACKPORT_BUILD_RADIX_HELPERS) += lib-radix-tree-helpers.o
+compat-$(CPTCFG_BACKPORT_BUILD_WW_MUTEX) += kernel/ww_mutex.o
new file mode 100644
@@ -0,0 +1,667 @@
+/*
+ * Copyright (c) 2013 Luis R. Rodriguez <mcgrof@do-not-panic.com>
+ *
+ * Backport ww mutex for older kernels. This is not supported when
+ * DEBUG_MUTEXES or DEBUG_LOCK_ALLOC is enabled.
+ *
+ * Taken from: kernel/mutex.c - via linux-stable v3.11-rc2
+ *
+ * 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 <asm/mutex.h>
+#include <linux/sched.h>
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,9,0)
+#include <linux/sched/rt.h>
+#endif
+#include <linux/export.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/debug_locks.h>
+#include <linux/version.h>
+
+/*
+ * A negative mutex count indicates that waiters are sleeping waiting for the
+ * mutex.
+ */
+#define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0)
+
+#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
+
+
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,10,0) /* 2bd2c92c and 41fcb9f2 */
+/*
+ * 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.
+ */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(3,10,0)
+static noinline
+#endif
+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)
+{
+ int retval = 1;
+
+ rcu_read_lock();
+ if (lock->owner)
+ retval = lock->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;
+}
+#else /* Backport 2bd2c92c: help keep backport_mutex_lock_common() clean */
+
+struct mspin_node {
+};
+#define MLOCK(mutex) NULL
+
+static noinline
+void mspin_lock(struct mspin_node **lock, struct mspin_node *node)
+{
+}
+
+static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node)
+{
+}
+
+static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
+{
+}
+
+int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
+{
+}
+
+static inline int mutex_can_spin_on_owner(struct mutex *lock)
+{
+ return 1;
+}
+#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(3,10,0) */
+#endif /* CONFIG_MUTEX_SPIN_ON_OWNER */
+
+/*
+ * 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);
+}
+
+/**
+ * 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) {
+ if (lock->ctx->acquired > 0)
+ lock->ctx->acquired--;
+ lock->ctx = NULL;
+ }
+
+ __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath);
+}
+EXPORT_SYMBOL_GPL(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)) {
+ return -EDEADLK;
+ }
+
+ return 0;
+}
+
+static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
+ struct ww_acquire_ctx *ww_ctx)
+{
+ 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);
+}
+
+/**
+ * backport_schedule_preempt_disabled - called with preemption disabled
+ *
+ * Backports c5491ea7. This is not exported so we leave it
+ * here as this is the only current core user on backports.
+ * Although available on >= 3.4 its only for in-kernel code so
+ * we provide our own.
+ *
+ * Returns with preemption disabled. Note: preempt_count must be 1
+ */
+static void __sched backport_schedule_preempt_disabled(void)
+{
+ preempt_enable_no_resched();
+ schedule();
+ preempt_disable();
+}
+
+/*
+ * Lock a mutex (possibly interruptible), slowpath:
+ */
+static __always_inline int __sched
+__backport_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)
+{
+ 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 (!__builtin_constant_p(ww_ctx == NULL) && 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))
+ break;
+ }
+
+ /*
+ * 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);
+ break;
+ }
+
+ if ((atomic_read(&lock->count) == 1) &&
+ (atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
+ lock_acquired(&lock->dep_map, ip);
+ if (!__builtin_constant_p(ww_ctx == NULL)) {
+ 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)))
+ break;
+
+ /*
+ * 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);
+
+ /* We don't support DEBUG_MUTEXES on the backport */
+ /* 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;
+
+ if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, -1) == 1))
+ goto done;
+
+ lock_contended(&lock->dep_map, ip);
+
+ for (;;) {
+ /*
+ * Lets try to take the lock again - this is needed even if
+ * we get here for the first time (shortly after failing to
+ * acquire the lock), to make sure that we get a wakeup once
+ * it's unlocked. Later on, if we sleep, this is the
+ * operation that gives us the lock. We xchg it to -1, so
+ * that when we release the lock, we properly wake up the
+ * other waiters:
+ */
+ if (MUTEX_SHOW_NO_WAITER(lock) &&
+ (atomic_xchg(&lock->count, -1) == 1))
+ break;
+
+ /*
+ * got a signal? (This code gets eliminated in the
+ * TASK_UNINTERRUPTIBLE case.)
+ */
+ if (unlikely(signal_pending_state(state, task))) {
+ ret = -EINTR;
+ goto err;
+ }
+
+ if (!__builtin_constant_p(ww_ctx == NULL) && ww_ctx->acquired > 0) {
+ ret = __mutex_lock_check_stamp(lock, ww_ctx);
+ if (ret)
+ goto err;
+ }
+
+ __set_task_state(task, state);
+
+ /* didn't get the lock, go to sleep: */
+ spin_unlock_mutex(&lock->wait_lock, flags);
+ backport_schedule_preempt_disabled();
+ spin_lock_mutex(&lock->wait_lock, flags);
+ }
+
+done:
+ lock_acquired(&lock->dep_map, ip);
+ /* got the lock - rejoice! */
+ mutex_remove_waiter(lock, &waiter, current_thread_info());
+ mutex_set_owner(lock);
+
+ if (!__builtin_constant_p(ww_ctx == NULL)) {
+ struct ww_mutex *ww = container_of(lock,
+ struct ww_mutex,
+ base);
+ struct mutex_waiter *cur;
+
+ /*
+ * This branch gets optimized out for the common case,
+ * and is only important for ww_mutex_lock.
+ */
+
+ ww_mutex_lock_acquired(ww, ww_ctx);
+ ww->ctx = ww_ctx;
+
+ /*
+ * Give any possible sleeping processes the chance to wake up,
+ * so they can recheck if they have to back off.
+ */
+ list_for_each_entry(cur, &lock->wait_list, list) {
+ /* debug_mutex_wake_waiter(lock, cur); */
+ wake_up_process(cur->task);
+ }
+ }
+
+ /* set it to 0 if there are no waiters left: */
+ if (likely(list_empty(&lock->wait_list)))
+ atomic_set(&lock->count, 0);
+
+ spin_unlock_mutex(&lock->wait_lock, flags);
+
+ /* debug_mutex_free_waiter(&waiter); */
+ 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;
+}
+
+static noinline int __sched
+__ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+ return __backport_mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
+ NULL, _RET_IP_, ctx);
+}
+
+static noinline int __sched
+__ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
+ struct ww_acquire_ctx *ctx)
+{
+ return __backport_mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
+ NULL, _RET_IP_, ctx);
+}
+
+/**
+ * __mutex_fastpath_lock_retval - try to take the lock by moving the count
+ * from 1 to a 0 value
+ * @count: pointer of type atomic_t
+ *
+ * For backporting purposes we can't use the older kernel's
+ * __mutex_fastpath_lock_retval() since upon failure of a fastpath
+ * lock we want to call our a failure routine with more than one argument, in
+ * this case the context for ww mutexes. Refer to commit a41b56ef the
+ * argument increase. It'd be painful to backport all asm code for the
+ * supported architectures so instead lets penalize the backport ww mutex
+ * fastpath lock with the not so efficient generic atomic_dec_return()
+ * implementation.
+ *
+ * Change the count from 1 to a value lower than 1. This function returns 0
+ * if the fastpath succeeds, or -1 otherwise.
+ */
+static inline int
+__backport_mutex_fastpath_lock_retval(atomic_t *count)
+{
+ if (unlikely(atomic_dec_return(count) < 0))
+ return -1;
+ return 0;
+}
+
+int __sched
+__ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+ int ret;
+
+ might_sleep();
+
+ ret = __backport_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_GPL(__ww_mutex_lock);
+
+int __sched
+__ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
+{
+ int ret;
+
+ might_sleep();
+
+ ret = __backport_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_GPL(__ww_mutex_lock_interruptible);