Date:	Fri, 27 Feb 2015 17:57:08 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	linux-kernel@...r.kernel.org
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Mike Galbraith <umgwanakikbuti@...il.com>
Subject: [PATCH 2/3] locking: ww_mutex: Allow to use rt_mutex instead of mutex for the baselock

This patch makes it possible to replace the base mutex by a rt_mutex. In
general one would not do this. In -RT we use rt_mutex instead of the
mutex by default and this means we need the ww_mutex functionality based
on rt_mutex.
This patch includes a slightly modified version of what we have in the
-RT try including Mike Galbraith's latest lockdep annotations fixups and
proper deadlock detection which was broken after the rt_mutex rework.

Cc: Mike Galbraith <umgwanakikbuti@...il.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 include/linux/ww_mutex.h |  87 ++++++++++++++++-
 kernel/locking/mutex.c   |  22 ++++-
 kernel/locking/rtmutex.c | 237 ++++++++++++++++++++++++++++++++++++++++++++---
 lib/Kconfig.debug        |   6 ++
 lib/locking-selftest.c   |   4 +
 5 files changed, 339 insertions(+), 17 deletions(-)

diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
index 6e5d5ee3138d..99793f00755c 100644
--- a/include/linux/ww_mutex.h
+++ b/include/linux/ww_mutex.h
@@ -15,6 +15,7 @@
 #define __LINUX_WW_MUTEX_H
 
 #include <linux/mutex.h>
+#include <linux/rtmutex.h>
 
 struct ww_class {
 	atomic_long_t stamp;
@@ -42,8 +43,19 @@ struct ww_acquire_ctx {
 #endif
 };
 
+struct rt_mutex_base_lock {
+	struct rt_mutex lock;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map      dep_map;
+#endif
+};
+
 struct ww_mutex {
+#ifdef CONFIG_WW_MUTEX_RTMUTEX
+	struct rt_mutex_base_lock base;
+#else
 	struct mutex base;
+#endif
 	struct ww_acquire_ctx *ctx;
 #ifdef CONFIG_DEBUG_MUTEXES
 	struct ww_class *ww_class;
@@ -62,9 +74,15 @@ struct ww_mutex {
 		, .acquire_name = #ww_class "_acquire" \
 		, .mutex_name = #ww_class "_mutex" }
 
-#define __WW_MUTEX_INITIALIZER(lockname, class) \
+#ifdef CONFIG_WW_MUTEX_RTMUTEX
+# define __WW_MUTEX_INITIALIZER(lockname, class) \
+		{ .base = { \__RT_MUTEX_INITIALIZER(lockname) } \
+		__WW_CLASS_MUTEX_INITIALIZER(lockname, class) }
+#else
+# define __WW_MUTEX_INITIALIZER(lockname, class) \
 		{ .base = { \__MUTEX_INITIALIZER(lockname) } \
 		__WW_CLASS_MUTEX_INITIALIZER(lockname, class) }
+#endif
 
 #define DEFINE_WW_CLASS(classname) \
 	struct ww_class classname = __WW_CLASS_INITIALIZER(classname)
@@ -72,6 +90,71 @@ struct ww_mutex {
 #define DEFINE_WW_MUTEX(mutexname, ww_class) \
 	struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class)
 
+#ifdef CONFIG_WW_MUTEX_RTMUTEX
+
+static inline void __ww_mutex_init(struct rt_mutex_base_lock *lock,
+				   struct ww_class *ww_class)
+{
+	__rt_mutex_init(&lock->lock, ww_class->mutex_name);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	/*
+	 * Make sure we are not reinitializing a held lock:
+	 */
+	debug_check_no_locks_freed(lock, sizeof(*lock));
+	lockdep_init_map(&lock->dep_map, ww_class->mutex_name,
+			 &ww_class->mutex_key, 0);
+#endif
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+	lock->lock.save_state = 0;
+#endif
+}
+
+static inline void __ww_mutex_lock_lock(struct rt_mutex_base_lock *lock)
+{
+	mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
+	rt_mutex_lock(&lock->lock);
+}
+
+static inline int
+__ww_mutex_lock_interruptible_lock(struct rt_mutex_base_lock *lock)
+{
+	int ret;
+
+	mutex_acquire(&lock->dep_map, 0, 0, _RET_IP_);
+	ret = rt_mutex_lock_interruptible(&lock->lock);
+	if (ret)
+		mutex_release(&lock->dep_map, 1, _RET_IP_);
+	return ret;
+}
+
+static inline int __ww_mutex_trylock_lock(struct rt_mutex_base_lock *lock)
+{
+	int ret;
+
+	ret = rt_mutex_trylock(&lock->lock);
+	if (ret)
+		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+	return ret;
+}
+
+static inline void __ww_mutex_destroy_lock(struct rt_mutex_base_lock *lock)
+{
+	rt_mutex_destroy(&lock->lock);
+}
+
+static inline bool __ww_mutex_is_locked_lock(struct rt_mutex_base_lock *lock)
+{
+	return rt_mutex_is_locked(&lock->lock);
+}
+
+static inline void __ww_mutex_unlock_lock(struct rt_mutex_base_lock *lock)
+{
+	mutex_release(&lock->dep_map, 1, _RET_IP_);
+	rt_mutex_unlock(&lock->lock);
+}
+
+#else
+
 static inline void __ww_mutex_init(struct mutex *lock,
 				   struct ww_class *ww_class)
 {
@@ -108,6 +191,8 @@ static inline void __ww_mutex_unlock_lock(struct mutex *lock)
 	mutex_unlock(lock);
 }
 
+#endif
+
 /**
  * ww_mutex_init - initialize the w/w mutex
  * @lock: the mutex to be initialized
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 16b2d3cc88b0..0a652ba46081 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -106,6 +106,7 @@ void __sched mutex_lock(struct mutex *lock)
 EXPORT_SYMBOL(mutex_lock);
 #endif
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 static __always_inline void ww_mutex_lock_acquired(struct ww_mutex *ww,
 						   struct ww_acquire_ctx *ww_ctx)
 {
@@ -215,6 +216,7 @@ ww_mutex_set_context_slowpath(struct ww_mutex *lock,
 		wake_up_process(cur->task);
 	}
 }
+#endif
 
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
 /*
@@ -328,6 +330,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
 	while (true) {
 		struct task_struct *owner;
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 		if (use_ww_ctx && ww_ctx->acquired > 0) {
 			struct ww_mutex *ww;
 
@@ -343,7 +346,7 @@ static bool mutex_optimistic_spin(struct mutex *lock,
 			if (READ_ONCE(ww->ctx))
 				break;
 		}
-
+#endif
 		/*
 		 * If there's an owner, wait for it to either
 		 * release the lock or go to sleep.
@@ -356,12 +359,14 @@ static bool mutex_optimistic_spin(struct mutex *lock,
 		if (mutex_try_to_acquire(lock)) {
 			lock_acquired(&lock->dep_map, ip);
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 			if (use_ww_ctx) {
 				struct ww_mutex *ww;
 				ww = container_of(lock, struct ww_mutex, base);
 
 				ww_mutex_set_context_fastpath(ww, ww_ctx);
 			}
+#endif
 
 			mutex_set_owner(lock);
 			osq_unlock(&lock->osq);
@@ -445,6 +450,7 @@ void __sched mutex_unlock(struct mutex *lock)
 
 EXPORT_SYMBOL(mutex_unlock);
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 /**
  * ww_mutex_unlock - release the w/w mutex
  * @lock: the mutex to be released
@@ -506,6 +512,7 @@ __ww_mutex_lock_check_stamp(struct mutex *lock, struct ww_acquire_ctx *ctx)
 
 	return 0;
 }
+#endif
 
 /*
  * Lock a mutex (possibly interruptible), slowpath:
@@ -570,12 +577,13 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 			ret = -EINTR;
 			goto err;
 		}
-
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 		if (use_ww_ctx && ww_ctx->acquired > 0) {
 			ret = __ww_mutex_lock_check_stamp(lock, ww_ctx);
 			if (ret)
 				goto err;
 		}
+#endif
 
 		__set_task_state(task, state);
 
@@ -597,11 +605,12 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 	lock_acquired(&lock->dep_map, ip);
 	mutex_set_owner(lock);
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 	if (use_ww_ctx) {
 		struct ww_mutex *ww = container_of(lock, struct ww_mutex, base);
 		ww_mutex_set_context_slowpath(ww, ww_ctx);
 	}
-
+#endif
 	spin_unlock_mutex(&lock->wait_lock, flags);
 	preempt_enable();
 	return 0;
@@ -655,6 +664,7 @@ mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
 
 EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 static inline int
 ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 {
@@ -711,7 +721,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);
-
+#endif
 #endif
 
 /*
@@ -840,6 +850,7 @@ __mutex_lock_interruptible_slowpath(struct mutex *lock)
 				   NULL, _RET_IP_, NULL, 0);
 }
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 static noinline int __sched
 __ww_mutex_lock_slowpath(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 {
@@ -854,6 +865,7 @@ __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
 	return __mutex_lock_common(&lock->base, TASK_INTERRUPTIBLE, 0,
 				   NULL, _RET_IP_, ctx, 1);
 }
+#endif
 
 #endif
 
@@ -915,6 +927,7 @@ int __sched mutex_trylock(struct mutex *lock)
 EXPORT_SYMBOL(mutex_trylock);
 
 #ifndef CONFIG_DEBUG_LOCK_ALLOC
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 int __sched
 __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 {
@@ -952,6 +965,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
 EXPORT_SYMBOL(__ww_mutex_lock_interruptible);
 
 #endif
+#endif
 
 /**
  * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index e16e5542bf13..6d7d72ffa619 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -16,6 +16,7 @@
 #include <linux/sched/rt.h>
 #include <linux/sched/deadline.h>
 #include <linux/timer.h>
+#include <linux/ww_mutex.h>
 
 #include "rtmutex_common.h"
 
@@ -738,6 +739,31 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task,
 	return ret;
 }
 
+static int __sched __mutex_lock_check_stamp(struct rt_mutex *lock,
+					    struct ww_acquire_ctx *ctx)
+{
+#ifdef CONFIG_WW_MUTEX_RTMUTEX
+	struct ww_mutex *ww = container_of(lock, struct ww_mutex, base.lock);
+	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;
+	}
+#endif
+	return 0;
+}
+
 /*
  * Try to take an rt-mutex
  *
@@ -1097,7 +1123,8 @@ void rt_mutex_adjust_pi(struct task_struct *task)
 static int __sched
 __rt_mutex_slowlock(struct rt_mutex *lock, int state,
 		    struct hrtimer_sleeper *timeout,
-		    struct rt_mutex_waiter *waiter)
+		    struct rt_mutex_waiter *waiter,
+		    struct ww_acquire_ctx *ww_ctx)
 {
 	int ret = 0;
 
@@ -1120,6 +1147,12 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state,
 				break;
 		}
 
+		if (ww_ctx && ww_ctx->acquired > 0) {
+			ret = __mutex_lock_check_stamp(lock, ww_ctx);
+			if (ret)
+				break;
+		}
+
 		raw_spin_unlock(&lock->wait_lock);
 
 		debug_rt_mutex_print_deadlock(waiter);
@@ -1154,13 +1187,84 @@ static void rt_mutex_handle_deadlock(int res, int detect_deadlock,
 	}
 }
 
+#ifdef CONFIG_WW_MUTEX_RTMUTEX
+static 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++;
+}
+#endif
+
+static void ww_mutex_account_lock(struct rt_mutex *lock,
+				  struct ww_acquire_ctx *ww_ctx)
+{
+#ifdef CONFIG_WW_MUTEX_RTMUTEX
+	struct ww_mutex *ww = container_of(lock, struct ww_mutex, base.lock);
+	struct rt_mutex_waiter *waiter, *n;
+
+	/*
+	 * 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.
+	 */
+	rbtree_postorder_for_each_entry_safe(waiter, n, &lock->waiters,
+					     tree_entry) {
+		/* XXX debug rt mutex waiter wakeup */
+
+		BUG_ON(waiter->lock != lock);
+		wake_up_process(waiter->task);
+	}
+#endif
+}
+
 /*
  * Slow path lock function:
  */
 static int __sched
 rt_mutex_slowlock(struct rt_mutex *lock, int state,
 		  struct hrtimer_sleeper *timeout,
-		  enum rtmutex_chainwalk chwalk)
+		  enum rtmutex_chainwalk chwalk,
+		  struct ww_acquire_ctx *ww_ctx)
 {
 	struct rt_mutex_waiter waiter;
 	int ret = 0;
@@ -1173,6 +1277,8 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 
 	/* Try to acquire the lock again: */
 	if (try_to_take_rt_mutex(lock, current, NULL)) {
+		if (ww_ctx)
+			ww_mutex_account_lock(lock, ww_ctx);
 		raw_spin_unlock(&lock->wait_lock);
 		return 0;
 	}
@@ -1190,12 +1296,22 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state,
 
 	if (likely(!ret))
 		/* sleep on the mutex */
-		ret = __rt_mutex_slowlock(lock, state, timeout, &waiter);
+		ret = __rt_mutex_slowlock(lock, state, timeout, &waiter,
+					  ww_ctx);
+	else if (ww_ctx) {
+		/* ww_mutex may need to return EALREADY insted of EDEADLK */
+		ret = __mutex_lock_check_stamp(lock, ww_ctx);
+		BUG_ON(!ret);
+	}
 
 	if (unlikely(ret)) {
 		if (rt_mutex_has_waiters(lock))
 			remove_waiter(lock, &waiter);
-		rt_mutex_handle_deadlock(ret, chwalk, &waiter);
+		/* ww_mutex need the error reported */
+		if (!ww_ctx)
+			rt_mutex_handle_deadlock(ret, chwalk, &waiter);
+	} else if (ww_ctx) {
+		ww_mutex_account_lock(lock, ww_ctx);
 	}
 
 	/*
@@ -1320,31 +1436,36 @@ rt_mutex_slowunlock(struct rt_mutex *lock)
  */
 static inline int
 rt_mutex_fastlock(struct rt_mutex *lock, int state,
+		  struct ww_acquire_ctx *ww_ctx,
 		  int (*slowfn)(struct rt_mutex *lock, int state,
 				struct hrtimer_sleeper *timeout,
-				enum rtmutex_chainwalk chwalk))
+				enum rtmutex_chainwalk chwalk,
+				struct ww_acquire_ctx *ww_ctx))
 {
 	if (likely(rt_mutex_cmpxchg(lock, NULL, current))) {
 		rt_mutex_deadlock_account_lock(lock, current);
 		return 0;
 	} else
-		return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK);
+		return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK,
+			      ww_ctx);
 }
 
 static inline int
 rt_mutex_timed_fastlock(struct rt_mutex *lock, int state,
 			struct hrtimer_sleeper *timeout,
 			enum rtmutex_chainwalk chwalk,
+			struct ww_acquire_ctx *ww_ctx,
 			int (*slowfn)(struct rt_mutex *lock, int state,
 				      struct hrtimer_sleeper *timeout,
-				      enum rtmutex_chainwalk chwalk))
+				      enum rtmutex_chainwalk chwalk,
+				      struct ww_acquire_ctx *ww_ctx))
 {
 	if (chwalk == RT_MUTEX_MIN_CHAINWALK &&
 	    likely(rt_mutex_cmpxchg(lock, NULL, current))) {
 		rt_mutex_deadlock_account_lock(lock, current);
 		return 0;
 	} else
-		return slowfn(lock, state, timeout, chwalk);
+		return slowfn(lock, state, timeout, chwalk, ww_ctx);
 }
 
 static inline int
@@ -1377,7 +1498,7 @@ void __sched rt_mutex_lock(struct rt_mutex *lock)
 {
 	might_sleep();
 
-	rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock);
+	rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, NULL, rt_mutex_slowlock);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock);
 
@@ -1394,7 +1515,8 @@ int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock)
 {
 	might_sleep();
 
-	return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock);
+	return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, NULL,
+				 rt_mutex_slowlock);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible);
 
@@ -1407,7 +1529,7 @@ int rt_mutex_timed_futex_lock(struct rt_mutex *lock,
 	might_sleep();
 
 	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
-				       RT_MUTEX_FULL_CHAINWALK,
+				       RT_MUTEX_FULL_CHAINWALK, NULL,
 				       rt_mutex_slowlock);
 }
 
@@ -1431,6 +1553,7 @@ rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout)
 
 	return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout,
 				       RT_MUTEX_MIN_CHAINWALK,
+				       NULL,
 				       rt_mutex_slowlock);
 }
 EXPORT_SYMBOL_GPL(rt_mutex_timed_lock);
@@ -1628,7 +1751,7 @@ int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
 	set_current_state(TASK_INTERRUPTIBLE);
 
 	/* sleep on the mutex */
-	ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter);
+	ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter, NULL);
 
 	if (unlikely(ret))
 		remove_waiter(lock, waiter);
@@ -1643,3 +1766,93 @@ int rt_mutex_finish_proxy_lock(struct rt_mutex *lock,
 
 	return ret;
 }
+
+#ifdef CONFIG_WW_MUTEX_RTMUTEX
+static 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_interruptible(struct ww_mutex *lock,
+					  struct ww_acquire_ctx *ww_ctx)
+{
+	int ret;
+
+	might_sleep();
+
+	mutex_acquire_nest(&lock->base.dep_map, 0, 0, &ww_ctx->dep_map,
+			   _RET_IP_);
+	ret = rt_mutex_slowlock(&lock->base.lock, TASK_INTERRUPTIBLE, NULL, 0,
+				ww_ctx);
+	if (ret)
+		mutex_release(&lock->base.dep_map, 1, _RET_IP_);
+	else if (!ret && ww_ctx->acquired > 1)
+		return ww_mutex_deadlock_injection(lock, ww_ctx);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__ww_mutex_lock_interruptible);
+
+int __sched __ww_mutex_lock(struct ww_mutex *lock,
+			    struct ww_acquire_ctx *ww_ctx)
+{
+	int ret;
+
+	might_sleep();
+
+	mutex_acquire_nest(&lock->base.dep_map, 0, 0, &ww_ctx->dep_map,
+			   _RET_IP_);
+	ret = rt_mutex_slowlock(&lock->base.lock, TASK_UNINTERRUPTIBLE, NULL, 0,
+				ww_ctx);
+	if (ret)
+		mutex_release(&lock->base.dep_map, 1, _RET_IP_);
+	else if (!ret && ww_ctx->acquired > 1)
+		return ww_mutex_deadlock_injection(lock, ww_ctx);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__ww_mutex_lock);
+
+void __sched ww_mutex_unlock(struct ww_mutex *lock)
+{
+	int nest = !!lock->ctx;
+
+	/*
+	 * The unlocking fastpath is the 0->1 transition from 'locked'
+	 * into 'unlocked' state:
+	 */
+	if (nest) {
+#ifdef CONFIG_DEBUG_MUTEXES
+		DEBUG_LOCKS_WARN_ON(!lock->ctx->acquired);
+#endif
+		if (lock->ctx->acquired > 0)
+			lock->ctx->acquired--;
+		lock->ctx = NULL;
+	}
+
+	mutex_release(&lock->base.dep_map, nest, _RET_IP_);
+	rt_mutex_unlock(&lock->base.lock);
+}
+EXPORT_SYMBOL(ww_mutex_unlock);
+#endif
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c5cefb3c009c..05b6a63f7218 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -921,6 +921,12 @@ config DEBUG_MUTEXES
 	 This feature allows mutex semantics violations to be detected and
 	 reported.
 
+config WW_MUTEX_RTMUTEX
+	bool "Wait/wound mutex: use RT-Mutex instead of the regular mutex"
+	help
+	  This replaces the mutex in ww_mutex by an rt_mutex. This is probably
+	  only useful for testing.
+
 config DEBUG_WW_MUTEX_SLOWPATH
 	bool "Wait/wound mutex debugging: Slowpath testing"
 	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 2c35e38b4013..84c017ac9c39 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -1192,6 +1192,7 @@ static void ww_test_normal(void)
 		WARN_ON(1);
 	WARN_ON(o.ctx != (void *)~0UL);
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 	/* mutex_lock_killable (and *_nested) */
 	o.ctx = (void *)~0UL;
 	ret = mutex_lock_killable(&o.base);
@@ -1200,6 +1201,7 @@ static void ww_test_normal(void)
 	else
 		WARN_ON(1);
 	WARN_ON(o.ctx != (void *)~0UL);
+#endif
 
 	/* trylock, succeeding */
 	o.ctx = (void *)~0UL;
@@ -1219,11 +1221,13 @@ static void ww_test_normal(void)
 	__ww_mutex_unlock_lock(&o.base);
 	WARN_ON(o.ctx != (void *)~0UL);
 
+#ifndef CONFIG_WW_MUTEX_RTMUTEX
 	/* nest_lock */
 	o.ctx = (void *)~0UL;
 	mutex_lock_nest_lock(&o.base, &t);
 	__ww_mutex_unlock_lock(&o.base);
 	WARN_ON(o.ctx != (void *)~0UL);
+#endif
 }
 
 static void ww_test_two_contexts(void)
-- 
2.1.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists