Keep a record of how many mutexes are held by any task. This allows cpu
scheduler code to use this information in decision making for tasks that
hold contended resources.

Signed-off-by: Con Kolivas <kernel@kolivas.org>

---
 include/linux/init_task.h |    1 +
 include/linux/sched.h     |    1 +
 kernel/fork.c             |    1 +
 kernel/mutex.c            |   25 +++++++++++++++++++++++--
 4 files changed, 26 insertions(+), 2 deletions(-)

Index: linux-2.6.20-ck1/include/linux/init_task.h
===================================================================
--- linux-2.6.20-ck1.orig/include/linux/init_task.h	2007-02-05 22:52:04.000000000 +1100
+++ linux-2.6.20-ck1/include/linux/init_task.h	2007-02-16 19:01:31.000000000 +1100
@@ -135,6 +135,7 @@ extern struct group_info init_groups;
 		.signal = {{0}}},					\
 	.blocked	= {{0}},					\
 	.alloc_lock	= __SPIN_LOCK_UNLOCKED(tsk.alloc_lock),		\
+	.mutexes_held	= 0,						\
 	.journal_info	= NULL,						\
 	.cpu_timers	= INIT_CPU_TIMERS(tsk.cpu_timers),		\
 	.fs_excl	= ATOMIC_INIT(0),				\
Index: linux-2.6.20-ck1/include/linux/sched.h
===================================================================
--- linux-2.6.20-ck1.orig/include/linux/sched.h	2007-02-16 19:01:31.000000000 +1100
+++ linux-2.6.20-ck1/include/linux/sched.h	2007-02-16 19:01:31.000000000 +1100
@@ -992,6 +992,7 @@ struct task_struct {
 	struct held_lock held_locks[MAX_LOCK_DEPTH];
 	unsigned int lockdep_recursion;
 #endif
+	unsigned long mutexes_held;
 
 /* journalling filesystem info */
 	void *journal_info;
Index: linux-2.6.20-ck1/kernel/fork.c
===================================================================
--- linux-2.6.20-ck1.orig/kernel/fork.c	2007-02-05 22:52:04.000000000 +1100
+++ linux-2.6.20-ck1/kernel/fork.c	2007-02-16 19:01:31.000000000 +1100
@@ -1058,6 +1058,7 @@ static struct task_struct *copy_process(
 	p->io_context = NULL;
 	p->io_wait = NULL;
 	p->audit_context = NULL;
+	p->mutexes_held = 0;
 	cpuset_fork(p);
 #ifdef CONFIG_NUMA
  	p->mempolicy = mpol_copy(p->mempolicy);
Index: linux-2.6.20-ck1/kernel/mutex.c
===================================================================
--- linux-2.6.20-ck1.orig/kernel/mutex.c	2007-02-05 22:52:04.000000000 +1100
+++ linux-2.6.20-ck1/kernel/mutex.c	2007-02-16 19:01:31.000000000 +1100
@@ -60,6 +60,16 @@ EXPORT_SYMBOL(__mutex_init);
 static void fastcall noinline __sched
 __mutex_lock_slowpath(atomic_t *lock_count);
 
+static inline void inc_mutex_count(void)
+{
+	current->mutexes_held++;
+}
+
+static inline void dec_mutex_count(void)
+{
+	current->mutexes_held--;
+}
+
 /***
  * mutex_lock - acquire the mutex
  * @lock: the mutex to be acquired
@@ -89,6 +99,7 @@ void inline fastcall __sched mutex_lock(
 	 * 'unlocked' into 'locked' state.
 	 */
 	__mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath);
+	inc_mutex_count();
 }
 
 EXPORT_SYMBOL(mutex_lock);
@@ -114,6 +125,7 @@ void fastcall __sched mutex_unlock(struc
 	 * into 'unlocked' state:
 	 */
 	__mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath);
+	dec_mutex_count();
 }
 
 EXPORT_SYMBOL(mutex_unlock);
@@ -283,9 +295,14 @@ __mutex_lock_interruptible_slowpath(atom
  */
 int fastcall __sched mutex_lock_interruptible(struct mutex *lock)
 {
+	int ret;
+
 	might_sleep();
-	return __mutex_fastpath_lock_retval
+	ret = __mutex_fastpath_lock_retval
 			(&lock->count, __mutex_lock_interruptible_slowpath);
+	if (likely(!ret))
+		inc_mutex_count();
+	return ret;
 }
 
 EXPORT_SYMBOL(mutex_lock_interruptible);
@@ -340,8 +357,12 @@ static inline int __mutex_trylock_slowpa
  */
 int fastcall __sched mutex_trylock(struct mutex *lock)
 {
-	return __mutex_fastpath_trylock(&lock->count,
+	int ret = __mutex_fastpath_trylock(&lock->count,
 					__mutex_trylock_slowpath);
+
+	if (likely(ret))
+		inc_mutex_count();
+	return ret;
 }
 
 EXPORT_SYMBOL(mutex_trylock);