new file mode 100644
@@ -0,0 +1,136 @@
+Reservation type mutexes
+---
+
+Please read mutex-design.txt first, as it applies to reservation mutexes too.
+
+GPU's do operations that commonly involve many buffers. Those buffers
+can be shared across contexts/processes, exist in different memory
+domains (for example VRAM vs system memory), and so on. And with
+PRIME / dmabuf, they can even be shared across devices. So there are
+a handful of situations where the driver needs to wait for buffers to
+become ready. If you think about this in terms of waiting on a buffer
+mutex for it to become available, this presents a problem because
+there is no way to guarantee that buffers appear in a execbuf/batch in
+the same order in all contexts. That is directly under control of
+userspace, and a result of the sequence of GL calls that an application
+makes. Which results in the potential for deadlock. The problem gets
+more complex when you consider that the kernel may need to migrate the
+buffer(s) into VRAM before the GPU operates on the buffer(s), which
+may in turn require evicting some other buffers (and you don't want to
+evict other buffers which are already queued up to the GPU), but for a
+simplified understanding of the problem you can ignore this.
+
+The algorithm that TTM came up with for dealing with this problem is
+quite simple. For each group of buffers (execbuf) that need to be
+locked, the caller would be assigned a unique reservation_id, from a
+global counter. In case of deadlock while locking all the buffers
+associated with a execbuf, the one with the lowest reservation_id
+wins, and the one with the higher reservation_id unlocks all of the
+buffers that it has already locked, and then tries again.
+
+How it is used:
+---------------
+
+A very simplified version:
+
+ int lock_execbuf(execbuf, ticket)
+ {
+ struct buf *res_buf = NULL;
+
+ /* acquiring locks, before queuing up to GPU: */
+ *ticket = assign_global_seqno();
+
+ retry:
+ for (buf in execbuf->buffers) {
+ if (buf == res_buf) {
+ res_buf = NULL;
+ continue;
+ }
+ ret = mutex_reserve_lock(&buf->lock, ticket, ticket->seqno);
+ if (ret < 0)
+ goto err;
+ }
+
+ /* now everything is good to go, submit job to GPU: */
+ ...
+
+ return 0;
+
+ err:
+ for (all buf2 before buf in execbuf->buffers)
+ mutex_unreserve_unlock(&buf2->lock);
+ if (res_buf)
+ mutex_unreserve_unlock(&res_buf->lock);
+
+ if (ret == -EAGAIN) {
+ /* we lost out in a seqno race, lock and retry.. */
+ mutex_reserve_lock_slow(&buf->lock, ticket, ticket->seqno);
+ res_buf = buf;
+ goto retry;
+ }
+ release_global_seqno(ticket);
+
+ return ret;
+ }
+
+ int unlock_execbuf(execbuf, ticket)
+ {
+ /* when GPU is finished; */
+ for (buf in execbuf->buffers)
+ mutex_unreserve_unlock(&buf->lock);
+ release_global_seqno(ticket);
+ }
+
+Functions:
+----------
+
+mutex_reserve_lock, and mutex_reserve_lock_interruptible:
+ Lock a reservation_lock with a reservation_id set. reservation_id must not
+ be set to 0, since this is a special value that means no reservation_id.
+
+ Normally if reservation_id is not set, or is older than the
+ reservation_id which is currently set on the mutex, the behavior will
+ be to wait normally. However, if the reservation_id is newer than
+ the current reservation_id, -EAGAIN will be returned.
+
+ These functions will return -EDEADLK instead of -EAGAIN if
+ reservation_id is the same as the reservation_id that's attempted to
+ lock the mutex with, since in that case you presumably attempted to
+ lock the same lock twice.
+
+mutex_reserve_lock_slow and mutex_reserve_lock_intr_slow:
+ Similar to mutex_reserve_lock, except it won't backoff with -EAGAIN.
+ This is useful when mutex_reserve_lock failed with -EAGAIN, and you
+ unreserved all reservation_locks so no deadlock can occur.
+
+mutex_unreserve_unlock:
+ Unlock a reservation_lock reserved with one of the mutex_reserve_*lock*
+ calls.
+
+Design:
+ ticket_mutex encapsulates a struct mutex, this means no extra overhead for
+ normal mutex locks, which are far more common. As such there is only a small
+ increase in code size if reservation mutexes are not used.
+
+ In general, not much contention is expected. The locks are intended to
+ serialize access to resources for devices. The only way to make wakeups
+ smarter would be at the cost of adding a field to struct mutex_waiter. This
+ would add overhead to all cases where normal mutexes are used, and
+ ticket_mutexes are less performance sensitive. For this reason
+ mutex_reserve_lock wakes up all waiters, so they can recheck themselves.
+
+Lockdep:
+ Lockdep operates on classes of locks. Ideally there should be only 2 lockdep
+ classes, one for the reservation_id itself, and one shared across all
+ reservation mutexes.
+
+ It may seem odd that reservation_id needs a lock class, but it's needed for
+ lockdep to work correctly. Because the lock class of all reservation mutexes
+ are equal, without nesting lockdep will complain. Using multiple lockdep
+ classes will result in reduced effectiveness.
+
+ The reason only a single lockdep class is wanted for reservation mutexes is
+ because it's always nested to the reservation_id's "lock", or only a single
+ lock is taken without any nesting at all. In the latter case no more than 1
+ mutex should be locked at the same time, which lockdep can only verify
+ if the lock class is always the same.
@@ -62,6 +62,11 @@ struct mutex {
#endif
};
+struct ticket_mutex {
+ struct mutex base;
+ atomic_long_t reservation_id;
+};
+
/*
* This is the control structure for tasks blocked on mutex,
* which resides on the blocked task's kernel stack:
@@ -109,12 +114,24 @@ static inline void mutex_destroy(struct mutex *lock) {}
__DEBUG_MUTEX_INITIALIZER(lockname) \
__DEP_MAP_MUTEX_INITIALIZER(lockname) }
+#define __TICKET_MUTEX_INITIALIZER(lockname) \
+ { .base = __MUTEX_INITIALIZER(lockname) \
+ , .reservation_id = ATOMIC_LONG_INIT(0) }
+
#define DEFINE_MUTEX(mutexname) \
struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
extern void __mutex_init(struct mutex *lock, const char *name,
struct lock_class_key *key);
+static inline void __ticket_mutex_init(struct ticket_mutex *lock,
+ const char *name,
+ struct lock_class_key *key)
+{
+ __mutex_init(&lock->base, name, key);
+ atomic_long_set(&lock->reservation_id, 0);
+}
+
/**
* mutex_is_locked - is the mutex locked
* @lock: the mutex to be queried
@@ -133,26 +150,91 @@ static inline int mutex_is_locked(struct mutex *lock)
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
extern void _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest_lock);
+
extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
unsigned int subclass);
extern int __must_check mutex_lock_killable_nested(struct mutex *lock,
unsigned int subclass);
+extern int __must_check _mutex_reserve_lock(struct ticket_mutex *lock,
+ struct lockdep_map *nest_lock,
+ unsigned long reservation_id);
+
+extern int __must_check _mutex_reserve_lock_interruptible(struct ticket_mutex *,
+ struct lockdep_map *nest_lock,
+ unsigned long reservation_id);
+
+extern void _mutex_reserve_lock_slow(struct ticket_mutex *lock,
+ struct lockdep_map *nest_lock,
+ unsigned long reservation_id);
+
+extern int __must_check _mutex_reserve_lock_intr_slow(struct ticket_mutex *,
+ struct lockdep_map *nest_lock,
+ unsigned long reservation_id);
+
#define mutex_lock(lock) mutex_lock_nested(lock, 0)
#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
#define mutex_lock_killable(lock) mutex_lock_killable_nested(lock, 0)
#define mutex_lock_nest_lock(lock, nest_lock) \
do { \
- typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
+ typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
_mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
} while (0)
+#define mutex_reserve_lock(lock, nest_lock, reservation_id) \
+({ \
+ typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
+ _mutex_reserve_lock(lock, &(nest_lock)->dep_map, reservation_id); \
+})
+
+#define mutex_reserve_lock_interruptible(lock, nest_lock, reservation_id) \
+({ \
+ typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
+ _mutex_reserve_lock_interruptible(lock, &(nest_lock)->dep_map, \
+ reservation_id); \
+})
+
+#define mutex_reserve_lock_slow(lock, nest_lock, reservation_id) \
+do { \
+ typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
+ _mutex_reserve_lock_slow(lock, &(nest_lock)->dep_map, reservation_id); \
+} while (0)
+
+#define mutex_reserve_lock_intr_slow(lock, nest_lock, reservation_id) \
+({ \
+ typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
+ _mutex_reserve_lock_intr_slow(lock, &(nest_lock)->dep_map, \
+ reservation_id); \
+})
+
#else
extern void mutex_lock(struct mutex *lock);
extern int __must_check mutex_lock_interruptible(struct mutex *lock);
extern int __must_check mutex_lock_killable(struct mutex *lock);
+extern int __must_check _mutex_reserve_lock(struct ticket_mutex *lock,
+ unsigned long reservation_id);
+extern int __must_check _mutex_reserve_lock_interruptible(struct ticket_mutex *,
+ unsigned long reservation_id);
+
+extern void _mutex_reserve_lock_slow(struct ticket_mutex *lock,
+ unsigned long reservation_id);
+extern int __must_check _mutex_reserve_lock_intr_slow(struct ticket_mutex *,
+ unsigned long reservation_id);
+
+#define mutex_reserve_lock(lock, nest_lock, reservation_id) \
+ _mutex_reserve_lock(lock, reservation_id)
+
+#define mutex_reserve_lock_interruptible(lock, nest_lock, reservation_id) \
+ _mutex_reserve_lock_interruptible(lock, reservation_id)
+
+#define mutex_reserve_lock_slow(lock, nest_lock, reservation_id) \
+ _mutex_reserve_lock_slow(lock, reservation_id)
+
+#define mutex_reserve_lock_intr_slow(lock, nest_lock, reservation_id) \
+ _mutex_reserve_lock_intr_slow(lock, reservation_id)
+
# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
# define mutex_lock_killable_nested(lock, subclass) mutex_lock_killable(lock)
@@ -167,6 +249,8 @@ extern int __must_check mutex_lock_killable(struct mutex *lock);
*/
extern int mutex_trylock(struct mutex *lock);
extern void mutex_unlock(struct mutex *lock);
+extern void mutex_unreserve_unlock(struct ticket_mutex *lock);
+
extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
#ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX
@@ -127,16 +127,116 @@ void __sched mutex_unlock(struct mutex *lock)
EXPORT_SYMBOL(mutex_unlock);
+/**
+ * mutex_unreserve_unlock - release the mutex
+ * @lock: the mutex to be released
+ *
+ * Unlock a mutex that has been locked by this task previously
+ * with _mutex_reserve_lock*.
+ *
+ * This function must not be used in interrupt context. Unlocking
+ * of a unlocked mutex is not allowed.
+ */
+void __sched mutex_unreserve_unlock(struct ticket_mutex *lock)
+{
+ /*
+ * The unlocking fastpath is the 0->1 transition from 'locked'
+ * into 'unlocked' state:
+ */
+
+ /*
+ * mark mutex as no longer part of a reservation, next
+ * locker can set this again
+ */
+#ifdef CONFIG_DEBUG_MUTEXES
+ unsigned long rid;
+
+ rid = atomic_long_xchg(&lock->reservation_id, 0);
+
+ /*
+ * If this WARN_ON triggers, you used mutex_lock to acquire,
+ * but released with mutex_unreserve_unlock in this call.
+ */
+ DEBUG_LOCKS_WARN_ON(!rid);
+#else
+ atomic_long_set(&lock->reservation_id, 0);
+
+ /*
+ * 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(mutex_unreserve_unlock);
+
+static inline int __sched
+__mutex_lock_check_reserve(struct mutex *lock, unsigned long reservation_id)
+{
+ struct ticket_mutex *m = container_of(lock, struct ticket_mutex, base);
+ unsigned long cur_id;
+
+ cur_id = atomic_long_read(&m->reservation_id);
+ if (!cur_id)
+ return 0;
+
+ if (unlikely(reservation_id == cur_id))
+ return -EDEADLK;
+
+ if (unlikely(reservation_id - cur_id <= LONG_MAX))
+ return -EAGAIN;
+
+ return 0;
+}
+
+/*
+ * after acquiring lock with fastpath or when we lost out in contested
+ * slowpath, set reservation_id 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
+mutex_set_reservation_fastpath(struct ticket_mutex *lock,
+ unsigned long reservation_id)
+{
+ unsigned long flags;
+ struct mutex_waiter *cur;
+
+ atomic_long_set(&lock->reservation_id, reservation_id);
+
+ /*
+ * 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 reservation_id
+ */
+ 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 inline int __sched
+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 lockdep_map *nest_lock, unsigned long ip,
+ unsigned long reservation_id, bool res_slow)
{
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);
@@ -163,6 +263,12 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
for (;;) {
struct task_struct *owner;
+ if (!__builtin_constant_p(reservation_id) && !res_slow) {
+ ret = __mutex_lock_check_reserve(lock, reservation_id);
+ if (ret)
+ goto err_nowait;
+ }
+
/*
* If there's an owner, wait for it to either
* release the lock or go to sleep.
@@ -173,6 +279,13 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
lock_acquired(&lock->dep_map, ip);
+ if (res_slow) {
+ struct ticket_mutex *m;
+ m = container_of(lock, struct ticket_mutex, base);
+
+ mutex_set_reservation_fastpath(m, reservation_id);
+ }
+
mutex_set_owner(lock);
preempt_enable();
return 0;
@@ -228,15 +341,16 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
* TASK_UNINTERRUPTIBLE case.)
*/
if (unlikely(signal_pending_state(state, task))) {
- mutex_remove_waiter(lock, &waiter,
- task_thread_info(task));
- mutex_release(&lock->dep_map, 1, ip);
- spin_unlock_mutex(&lock->wait_lock, flags);
+ ret = -EINTR;
+ goto err;
+ }
- debug_mutex_free_waiter(&waiter);
- preempt_enable();
- return -EINTR;
+ if (!__builtin_constant_p(reservation_id) && !res_slow) {
+ ret = __mutex_lock_check_reserve(lock, reservation_id);
+ if (ret)
+ goto err;
}
+
__set_task_state(task, state);
/* didn't get the lock, go to sleep: */
@@ -251,6 +365,41 @@ done:
mutex_remove_waiter(lock, &waiter, current_thread_info());
mutex_set_owner(lock);
+ if (!__builtin_constant_p(reservation_id)) {
+ struct ticket_mutex *m = container_of(lock,
+ struct ticket_mutex,
+ base);
+ struct mutex_waiter *cur;
+
+ /*
+ * this should get optimized out for the common case,
+ * and is only important for _mutex_reserve_lock
+ */
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ unsigned long old_id;
+ old_id = atomic_long_xchg(&m->reservation_id, reservation_id);
+
+ /*
+ * If this WARN_ON triggers, you used mutex_lock to acquire,
+ * but released with mutex_unreserve_unlock in this call.
+ */
+ DEBUG_LOCKS_WARN_ON(old_id);
+#else
+ atomic_long_set(&m->reservation_id, reservation_id);
+#endif
+
+ /*
+ * give any possible sleeping processes the chance to wake up,
+ * so they can recheck if they have to back off from
+ * reservations
+ */
+ 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);
@@ -261,6 +410,19 @@ done:
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);
+
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
+err_nowait:
+#endif
+ mutex_release(&lock->dep_map, 1, ip);
+
+ preempt_enable();
+ return ret;
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -268,7 +430,8 @@ void __sched
mutex_lock_nested(struct mutex *lock, unsigned int subclass)
{
might_sleep();
- __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
+ __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
+ subclass, NULL, _RET_IP_, 0, 0);
}
EXPORT_SYMBOL_GPL(mutex_lock_nested);
@@ -277,7 +440,8 @@ 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_);
+ __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
+ 0, nest, _RET_IP_, 0, 0);
}
EXPORT_SYMBOL_GPL(_mutex_lock_nest_lock);
@@ -286,7 +450,8 @@ 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_);
+ return __mutex_lock_common(lock, TASK_KILLABLE,
+ subclass, NULL, _RET_IP_, 0, 0);
}
EXPORT_SYMBOL_GPL(mutex_lock_killable_nested);
@@ -295,10 +460,63 @@ mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
{
might_sleep();
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE,
- subclass, NULL, _RET_IP_);
+ subclass, NULL, _RET_IP_, 0, 0);
}
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
+
+int __sched
+_mutex_reserve_lock(struct ticket_mutex *lock, struct lockdep_map *nest,
+ unsigned long reservation_id)
+{
+ DEBUG_LOCKS_WARN_ON(!reservation_id);
+
+ might_sleep();
+ return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
+ 0, nest, _RET_IP_, reservation_id, 0);
+}
+EXPORT_SYMBOL_GPL(_mutex_reserve_lock);
+
+
+int __sched
+_mutex_reserve_lock_interruptible(struct ticket_mutex *lock,
+ struct lockdep_map *nest,
+ unsigned long reservation_id)
+{
+ DEBUG_LOCKS_WARN_ON(!reservation_id);
+
+ might_sleep();
+ return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
+ 0, nest, _RET_IP_, reservation_id, 0);
+}
+EXPORT_SYMBOL_GPL(_mutex_reserve_lock_interruptible);
+
+void __sched
+_mutex_reserve_lock_slow(struct ticket_mutex *lock, struct lockdep_map *nest,
+ unsigned long reservation_id)
+{
+ DEBUG_LOCKS_WARN_ON(!reservation_id);
+
+ might_sleep();
+ __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
+ nest, _RET_IP_, reservation_id, 1);
+}
+EXPORT_SYMBOL_GPL(_mutex_reserve_lock_slow);
+
+int __sched
+_mutex_reserve_lock_intr_slow(struct ticket_mutex *lock,
+ struct lockdep_map *nest,
+ unsigned long reservation_id)
+{
+ DEBUG_LOCKS_WARN_ON(!reservation_id);
+
+ might_sleep();
+ return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
+ nest, _RET_IP_, reservation_id, 1);
+}
+EXPORT_SYMBOL_GPL(_mutex_reserve_lock_intr_slow);
+
+
#endif
/*
@@ -401,20 +619,39 @@ __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_);
+ __mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0,
+ NULL, _RET_IP_, 0, 0);
}
static noinline int __sched
__mutex_lock_killable_slowpath(struct mutex *lock)
{
- return __mutex_lock_common(lock, TASK_KILLABLE, 0, NULL, _RET_IP_);
+ return __mutex_lock_common(lock, TASK_KILLABLE, 0,
+ NULL, _RET_IP_, 0, 0);
}
static noinline int __sched
__mutex_lock_interruptible_slowpath(struct mutex *lock)
{
- return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0, NULL, _RET_IP_);
+ return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, 0,
+ NULL, _RET_IP_, 0, 0);
+}
+
+static noinline int __sched
+__mutex_lock_reserve_slowpath(struct ticket_mutex *lock, unsigned long rid)
+{
+ return __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE, 0,
+ NULL, _RET_IP_, rid, 0);
+}
+
+static noinline int __sched
+__mutex_lock_interruptible_reserve_slowpath(struct ticket_mutex *lock,
+ unsigned long rid)
+{
+ return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
+ NULL, _RET_IP_, rid, 0);
}
+
#endif
/*
@@ -470,6 +707,63 @@ int __sched mutex_trylock(struct mutex *lock)
}
EXPORT_SYMBOL(mutex_trylock);
+#ifndef CONFIG_DEBUG_LOCK_ALLOC
+int __sched
+_mutex_reserve_lock(struct ticket_mutex *lock, unsigned long rid)
+{
+ int ret;
+
+ might_sleep();
+
+ ret = __mutex_fastpath_lock_retval(&lock->base.count);
+
+ if (likely(!ret)) {
+ mutex_set_reservation_fastpath(lock, rid);
+ mutex_set_owner(&lock->base);
+ } else
+ ret = __mutex_lock_reserve_slowpath(lock, rid);
+ return ret;
+}
+EXPORT_SYMBOL(_mutex_reserve_lock);
+
+int __sched
+_mutex_reserve_lock_interruptible(struct ticket_mutex *lock, unsigned long rid)
+{
+ int ret;
+
+ might_sleep();
+
+ ret = __mutex_fastpath_lock_retval(&lock->base.count);
+
+ if (likely(!ret)) {
+ mutex_set_reservation_fastpath(lock, rid);
+ mutex_set_owner(&lock->base);
+ } else
+ ret = __mutex_lock_interruptible_reserve_slowpath(lock, rid);
+ return ret;
+}
+EXPORT_SYMBOL(_mutex_reserve_lock_interruptible);
+
+void __sched
+_mutex_reserve_lock_slow(struct ticket_mutex *lock, unsigned long rid)
+{
+ might_sleep();
+ __mutex_lock_common(&lock->base, TASK_UNINTERRUPTIBLE,
+ 0, NULL, _RET_IP_, rid, 1);
+}
+EXPORT_SYMBOL(_mutex_reserve_lock_slow);
+
+int __sched
+_mutex_reserve_lock_intr_slow(struct ticket_mutex *lock, unsigned long rid)
+{
+ might_sleep();
+ return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE,
+ 0, NULL, _RET_IP_, rid, 1);
+}
+EXPORT_SYMBOL(_mutex_reserve_lock_intr_slow);
+
+#endif
+
/**
* atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
* @cnt: the atomic which we are to dec
New version. All of the documentation has been moved from the commit log to Documentation/reservation-mutex-design.txt Missing at the moment, maybe TODO? Add a lockdep check in the *_slow calls that verifies that the lock being nested into has no nested lock any more? This would be a check to make sure that mutex_unreserve_unlock has been called on all other locks correctly. Changes since RFC patch v1: - Updated to use atomic_long instead of atomic, since the reservation_id was a long. - added mutex_reserve_lock_slow and mutex_reserve_lock_intr_slow - removed mutex_locked_set_reservation_id (or w/e it was called) Changes since RFC patch v2: - remove use of __mutex_lock_retval_arg, add warnings when using wrong combination of mutex_(,reserve_)lock/unlock. Changes since v1: - Add __always_inline to __mutex_lock_common, otherwise reservation paths can be triggered from normal locks, because __builtin_constant_p might evaluate to false for the constant 0 in that case. Tests for this have been added in the next patch. - Updated documentation slightly. Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com> --- Documentation/reservation-mutex-design.txt | 136 ++++++++++++ include/linux/mutex.h | 86 +++++++ kernel/mutex.c | 326 +++++++++++++++++++++++++++- 3 files changed, 531 insertions(+), 17 deletions(-) create mode 100644 Documentation/reservation-mutex-design.txt