From: Ingo Molnar <mingo@elte.hu>

With the lock validator we detect mutex deadlocks (and more), the mutex
deadlock checking code is both redundant and slower.  So remove it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 kernel/mutex-debug.c |  126 -----------------------------------------
 lib/Kconfig.debug    |    8 --
 2 files changed, 1 insertion(+), 133 deletions(-)

diff -puN kernel/mutex-debug.c~better-lock-debugging-remove-mutex-deadlock-checking-code kernel/mutex-debug.c
--- devel/kernel/mutex-debug.c~better-lock-debugging-remove-mutex-deadlock-checking-code	2006-06-09 15:23:06.000000000 -0700
+++ devel-akpm/kernel/mutex-debug.c	2006-06-09 15:23:06.000000000 -0700
@@ -24,128 +24,6 @@
 
 #include "mutex-debug.h"
 
-static void printk_task(struct task_struct *p)
-{
-	if (p)
-		printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio);
-	else
-		printk("<none>");
-}
-
-static void printk_ti(struct thread_info *ti)
-{
-	if (ti)
-		printk_task(ti->task);
-	else
-		printk("<none>");
-}
-
-static void printk_lock(struct mutex *lock, int print_owner)
-{
-#ifdef CONFIG_PROVE_MUTEX_LOCKING
-	printk(" [%p] {%s}\n", lock, lock->dep_map.name);
-#else
-	printk(" [%p]\n", lock);
-#endif
-
-	if (print_owner && lock->owner) {
-		printk(".. held by:  ");
-		printk_ti(lock->owner);
-		printk("\n");
-	}
-}
-
-static void report_deadlock(struct task_struct *task, struct mutex *lock,
-			    struct mutex *lockblk)
-{
-	printk("\n%s/%d is trying to acquire this lock:\n",
-		current->comm, current->pid);
-	printk_lock(lock, 1);
-	debug_show_held_locks(current);
-
-	if (lockblk) {
-		printk("but %s/%d is deadlocking current task %s/%d!\n\n",
-			task->comm, task->pid, current->comm, current->pid);
-		printk("\n%s/%d is blocked on this lock:\n",
-			task->comm, task->pid);
-		printk_lock(lockblk, 1);
-
-		debug_show_held_locks(task);
-
-		printk("\n%s/%d's [blocked] stackdump:\n\n",
-			task->comm, task->pid);
-		show_stack(task, NULL);
-	}
-
-	printk("\n%s/%d's [current] stackdump:\n\n",
-		current->comm, current->pid);
-	dump_stack();
-	debug_show_all_locks();
-	printk("[ turning off deadlock detection. Please report this. ]\n\n");
-	local_irq_disable();
-}
-
-/*
- * Recursively check for mutex deadlocks:
- */
-static int check_deadlock(struct mutex *lock, int depth, struct thread_info *ti)
-{
-	struct mutex *lockblk;
-	struct task_struct *task;
-
-	if (!debug_locks)
-		return 0;
-
-	ti = lock->owner;
-	if (!ti)
-		return 0;
-
-	task = ti->task;
-	/*
-	 * In the PROVE_MUTEX_LOCKING we are tracking all held
-	 * locks already, which allows us to optimize this:
-	 */
-#ifdef CONFIG_PROVE_MUTEX_LOCKING
-	if (!task->lockdep_depth)
-		return 0;
-#endif
-	lockblk = NULL;
-	if (task->blocked_on)
-		lockblk = task->blocked_on->lock;
-
-	/* Self-deadlock: */
-	if (current == task) {
-		debug_locks_off();
-		if (depth)
-			return 1;
-		printk("\n==========================================\n");
-		printk(  "[ BUG: lock recursion deadlock detected! |\n");
-		printk(  "------------------------------------------\n");
-		report_deadlock(task, lock, NULL);
-		return 0;
-	}
-
-	/* Ugh, something corrupted the lock data structure? */
-	if (depth > 20) {
-		debug_locks_off();
-		printk("\n===========================================\n");
-		printk(  "[ BUG: infinite lock dependency detected!? |\n");
-		printk(  "-------------------------------------------\n");
-		report_deadlock(task, lock, lockblk);
-		return 0;
-	}
-
-	/* Recursively check for dependencies: */
-	if (lockblk && check_deadlock(lockblk, depth+1, ti)) {
-		printk("\n============================================\n");
-		printk(  "[ BUG: circular locking deadlock detected! ]\n");
-		printk(  "--------------------------------------------\n");
-		report_deadlock(task, lock, lockblk);
-		return 0;
-	}
-	return 0;
-}
-
 /*
  * Must be called with lock->wait_lock held.
  */
@@ -179,9 +57,7 @@ void debug_mutex_add_waiter(struct mutex
 			    struct thread_info *ti)
 {
 	SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock));
-#ifdef CONFIG_DEBUG_MUTEX_DEADLOCKS
-	check_deadlock(lock, 0, ti);
-#endif
+
 	/* Mark the current thread as blocked on the lock: */
 	ti->task->blocked_on = waiter;
 	waiter->lock = lock;
diff -puN lib/Kconfig.debug~better-lock-debugging-remove-mutex-deadlock-checking-code lib/Kconfig.debug
--- devel/lib/Kconfig.debug~better-lock-debugging-remove-mutex-deadlock-checking-code	2006-06-09 15:23:06.000000000 -0700
+++ devel-akpm/lib/Kconfig.debug	2006-06-09 15:23:06.000000000 -0700
@@ -133,14 +133,6 @@ config DEBUG_MUTEX_ALLOC
 	 (kfree(), kmem_cache_free(), free_pages(), vfree(), etc.),
 	 or whether there is any lock held during task exit.
 
-config DEBUG_MUTEX_DEADLOCKS
-	bool "Detect mutex related deadlocks"
-	default y
-	depends on DEBUG_MUTEXES
-	help
-	 This feature will automatically detect and report mutex related
-	 deadlocks, as they happen.
-
 config DEBUG_RT_MUTEXES
 	bool "RT Mutex debugging, deadlock detection"
 	depends on DEBUG_KERNEL && RT_MUTEXES
_