[PATCH] lockdep: remove mutex deadlock checking code

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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/mutex-debug.c b/kernel/mutex-debug.c
index fe0e9f2..a92de14 100644 (file)
--- a/kernel/mutex-debug.c
+++ b/kernel/mutex-debug.c
@@ -51,321 +51,6 @@ LIST_HEAD(debug_mutex_held_locks);
  */
 int debug_mutex_on = 1;
 
-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_task_short(struct task_struct *p)
-{
-       if (p)
-               printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio);
-       else
-               printk("<none>");
-}
-
-static void printk_lock(struct mutex *lock, int print_owner)
-{
-       printk(" [%p] {%s}\n", lock, lock->name);
-
-       if (print_owner && lock->owner) {
-               printk(".. held by:  ");
-               printk_ti(lock->owner);
-               printk("\n");
-       }
-       if (lock->owner) {
-               printk("... acquired at:               ");
-               print_symbol("%s\n", lock->acquire_ip);
-       }
-}
-
-/*
- * printk locks held by a task:
- */
-static void show_task_locks(struct task_struct *p)
-{
-       switch (p->state) {
-       case TASK_RUNNING:              printk("R"); break;
-       case TASK_INTERRUPTIBLE:        printk("S"); break;
-       case TASK_UNINTERRUPTIBLE:      printk("D"); break;
-       case TASK_STOPPED:              printk("T"); break;
-       case EXIT_ZOMBIE:               printk("Z"); break;
-       case EXIT_DEAD:                 printk("X"); break;
-       default:                        printk("?"); break;
-       }
-       printk_task(p);
-       if (p->blocked_on) {
-               struct mutex *lock = p->blocked_on->lock;
-
-               printk(" blocked on mutex:");
-               printk_lock(lock, 1);
-       } else
-               printk(" (not blocked on mutex)\n");
-}
-
-/*
- * printk all locks held in the system (if filter == NULL),
- * or all locks belonging to a single task (if filter != NULL):
- */
-void show_held_locks(struct task_struct *filter)
-{
-       struct list_head *curr, *cursor = NULL;
-       struct mutex *lock;
-       struct thread_info *t;
-       unsigned long flags;
-       int count = 0;
-
-       if (filter) {
-               printk("------------------------------\n");
-               printk("| showing all locks held by: |  (");
-               printk_task_short(filter);
-               printk("):\n");
-               printk("------------------------------\n");
-       } else {
-               printk("---------------------------\n");
-               printk("| showing all locks held: |\n");
-               printk("---------------------------\n");
-       }
-
-       /*
-        * Play safe and acquire the global trace lock. We
-        * cannot printk with that lock held so we iterate
-        * very carefully:
-        */
-next:
-       debug_spin_lock_save(&debug_mutex_lock, flags);
-       list_for_each(curr, &debug_mutex_held_locks) {
-               if (cursor && curr != cursor)
-                       continue;
-               lock = list_entry(curr, struct mutex, held_list);
-               t = lock->owner;
-               if (filter && (t != filter->thread_info))
-                       continue;
-               count++;
-               cursor = curr->next;
-               debug_spin_unlock_restore(&debug_mutex_lock, flags);
-
-               printk("\n#%03d:            ", count);
-               printk_lock(lock, filter ? 0 : 1);
-               goto next;
-       }
-       debug_spin_unlock_restore(&debug_mutex_lock, flags);
-       printk("\n");
-}
-
-void mutex_debug_show_all_locks(void)
-{
-       struct task_struct *g, *p;
-       int count = 10;
-       int unlock = 1;
-
-       printk("\nShowing all blocking locks in the system:\n");
-
-       /*
-        * Here we try to get the tasklist_lock as hard as possible,
-        * if not successful after 2 seconds we ignore it (but keep
-        * trying). This is to enable a debug printout even if a
-        * tasklist_lock-holding task deadlocks or crashes.
-        */
-retry:
-       if (!read_trylock(&tasklist_lock)) {
-               if (count == 10)
-                       printk("hm, tasklist_lock locked, retrying... ");
-               if (count) {
-                       count--;
-                       printk(" #%d", 10-count);
-                       mdelay(200);
-                       goto retry;
-               }
-               printk(" ignoring it.\n");
-               unlock = 0;
-       }
-       if (count != 10)
-               printk(" locked it.\n");
-
-       do_each_thread(g, p) {
-               show_task_locks(p);
-               if (!unlock)
-                       if (read_trylock(&tasklist_lock))
-                               unlock = 1;
-       } while_each_thread(g, p);
-
-       printk("\n");
-       show_held_locks(NULL);
-       printk("=============================================\n\n");
-
-       if (unlock)
-               read_unlock(&tasklist_lock);
-}
-
-static void report_deadlock(struct task_struct *task, struct mutex *lock,
-                           struct mutex *lockblk, unsigned long ip)
-{
-       printk("\n%s/%d is trying to acquire this lock:\n",
-               current->comm, current->pid);
-       printk_lock(lock, 1);
-       printk("... trying at:                 ");
-       print_symbol("%s\n", ip);
-       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);
-
-               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();
-       mutex_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, unsigned long ip)
-{
-       struct mutex *lockblk;
-       struct task_struct *task;
-
-       if (!debug_mutex_on)
-               return 0;
-
-       ti = lock->owner;
-       if (!ti)
-               return 0;
-
-       task = ti->task;
-       lockblk = NULL;
-       if (task->blocked_on)
-               lockblk = task->blocked_on->lock;
-
-       /* Self-deadlock: */
-       if (current == task) {
-               DEBUG_OFF();
-               if (depth)
-                       return 1;
-               printk("\n==========================================\n");
-               printk(  "[ BUG: lock recursion deadlock detected! |\n");
-               printk(  "------------------------------------------\n");
-               report_deadlock(task, lock, NULL, ip);
-               return 0;
-       }
-
-       /* Ugh, something corrupted the lock data structure? */
-       if (depth > 20) {
-               DEBUG_OFF();
-               printk("\n===========================================\n");
-               printk(  "[ BUG: infinite lock dependency detected!? |\n");
-               printk(  "-------------------------------------------\n");
-               report_deadlock(task, lock, lockblk, ip);
-               return 0;
-       }
-
-       /* Recursively check for dependencies: */
-       if (lockblk && check_deadlock(lockblk, depth+1, ti, ip)) {
-               printk("\n============================================\n");
-               printk(  "[ BUG: circular locking deadlock detected! ]\n");
-               printk(  "--------------------------------------------\n");
-               report_deadlock(task, lock, lockblk, ip);
-               return 0;
-       }
-       return 0;
-}
-
-/*
- * Called when a task exits, this function checks whether the
- * task is holding any locks, and reports the first one if so:
- */
-void mutex_debug_check_no_locks_held(struct task_struct *task)
-{
-       struct list_head *curr, *next;
-       struct thread_info *t;
-       unsigned long flags;
-       struct mutex *lock;
-
-       if (!debug_mutex_on)
-               return;
-
-       debug_spin_lock_save(&debug_mutex_lock, flags);
-       list_for_each_safe(curr, next, &debug_mutex_held_locks) {
-               lock = list_entry(curr, struct mutex, held_list);
-               t = lock->owner;
-               if (t != task->thread_info)
-                       continue;
-               list_del_init(curr);
-               DEBUG_OFF();
-               debug_spin_unlock_restore(&debug_mutex_lock, flags);
-
-               printk("BUG: %s/%d, lock held at task exit time!\n",
-                       task->comm, task->pid);
-               printk_lock(lock, 1);
-               if (lock->owner != task->thread_info)
-                       printk("exiting task is not even the owner??\n");
-               return;
-       }
-       debug_spin_unlock_restore(&debug_mutex_lock, flags);
-}
-
-/*
- * Called when kernel memory is freed (or unmapped), or if a mutex
- * is destroyed or reinitialized - this code checks whether there is
- * any held lock in the memory range of <from> to <to>:
- */
-void mutex_debug_check_no_locks_freed(const void *from, unsigned long len)
-{
-       struct list_head *curr, *next;
-       const void *to = from + len;
-       unsigned long flags;
-       struct mutex *lock;
-       void *lock_addr;
-
-       if (!debug_mutex_on)
-               return;
-
-       debug_spin_lock_save(&debug_mutex_lock, flags);
-       list_for_each_safe(curr, next, &debug_mutex_held_locks) {
-               lock = list_entry(curr, struct mutex, held_list);
-               lock_addr = lock;
-               if (lock_addr < from || lock_addr >= to)
-                       continue;
-               list_del_init(curr);
-               DEBUG_OFF();
-               debug_spin_unlock_restore(&debug_mutex_lock, flags);
-
-               printk("BUG: %s/%d, active lock [%p(%p-%p)] freed!\n",
-                       current->comm, current->pid, lock, from, to);
-               dump_stack();
-               printk_lock(lock, 1);
-               if (lock->owner != current_thread_info())
-                       printk("freeing task is not even the owner??\n");
-               return;
-       }
-       debug_spin_unlock_restore(&debug_mutex_lock, flags);
-}
-
 /*
  * Must be called with lock->wait_lock held.
  */
@@ -405,7 +90,6 @@ void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
                            struct thread_info *ti __IP_DECL__)
 {
        SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock));
-       check_deadlock(lock, 0, ti, ip);
        /* Mark the current thread as blocked on the lock: */
        ti->task->blocked_on = waiter;
        waiter->lock = lock;

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e4fcbd1..7b3863d 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -115,14 +115,6 @@ config DEBUG_PREEMPT
          if kernel code uses it in a preemption-unsafe way. Also, the kernel
          will detect preemption count underflows.
 
-config DEBUG_MUTEXES
-       bool "Mutex debugging, deadlock detection"
-       default n
-       depends on DEBUG_KERNEL
-       help
-        This allows mutex semantics violations and mutex related deadlocks
-        (lockups) to be detected and reported automatically.
-
 config DEBUG_RT_MUTEXES
        bool "RT Mutex debugging, deadlock detection"
        depends on DEBUG_KERNEL && RT_MUTEXES