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Subject[patch 06/15] Generic Mutex Subsystem, mutex-debug.patch

mutex implementation - add debugging code.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

----

kernel/mutex-debug.c | 444 +++++++++++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 8
2 files changed, 452 insertions(+)

Index: linux/kernel/mutex-debug.c
===================================================================
--- /dev/null
+++ linux/kernel/mutex-debug.c
@@ -0,0 +1,444 @@
+/*
+ * kernel/mutex-debug.c
+ *
+ * Debugging code for mutexes
+ *
+ * Started by Ingo Molnar:
+ *
+ * Copyright (C) 2004, 2005 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * lock debugging, locking tree, deadlock detection started by:
+ *
+ * Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey
+ * Released under the General Public License (GPL).
+ */
+
+/*
+ * We need a global lock when we walk through the multi-process
+ * lock tree. Only used in the deadlock-debugging case.
+ */
+static DEFINE_SPINLOCK(debug_lock);
+
+static LIST_HEAD(held_locks);
+
+/*
+ * deadlock detection flag. We turn it off when we detect
+ * the first problem because we dont want to recurse back
+ * into the tracing code when doing error printk or
+ * executing a BUG():
+ */
+static int debug_on = 1;
+
+#define debug_lock_irq(lock, ti) \
+ do { \
+ (void)(ti); \
+ local_irq_disable(); \
+ if (debug_on) \
+ spin_lock(lock); \
+ } while (0)
+
+#define debug_unlock(lock, ti) \
+ do { \
+ (void)(ti); \
+ if (debug_on) \
+ spin_unlock(lock); \
+ } while (0)
+
+#define debug_unlock_irq(lock, ti) \
+ do { \
+ (void)(ti); \
+ if (debug_on) \
+ spin_unlock(lock); \
+ local_irq_enable(); \
+ preempt_check_resched(); \
+ } while (0)
+
+#define debug_lock_irqsave(lock, flags, ti) \
+ do { \
+ (void)(ti); \
+ local_irq_save(flags); \
+ if (debug_on) \
+ spin_lock(lock); \
+ } while (0)
+
+#define debug_unlock_irqrestore(lock, flags, ti) \
+ do { \
+ (void)(ti); \
+ if (debug_on) \
+ spin_unlock(lock); \
+ local_irq_restore(flags); \
+ preempt_check_resched(); \
+ } while (0)
+
+#define DEBUG_OFF() \
+do { \
+ if (debug_on) { \
+ debug_on = 0; \
+ console_verbose(); \
+ if (spin_is_locked(&debug_lock)) \
+ spin_unlock(&debug_lock); \
+ } \
+} while (0)
+
+#define DEBUG_BUG() \
+do { \
+ if (debug_on) { \
+ DEBUG_OFF(); \
+ BUG(); \
+ } \
+} while (0)
+
+#define DEBUG_WARN_ON(c) \
+do { \
+ if (unlikely(c && debug_on)) { \
+ DEBUG_OFF(); \
+ WARN_ON(1); \
+ } \
+} while (0)
+
+# define DEBUG_BUG_ON(c) \
+do { \
+ if (unlikely(c)) \
+ DEBUG_BUG(); \
+} while (0)
+
+# define debug_local_irq_disable(ti) local_irq_disable()
+# define debug_local_irq_enable(ti) local_irq_enable()
+# define debug_local_irq_restore(flags, ti) local_irq_restore(flags)
+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)
+{
+ if (lock->name)
+ printk(" [%p] {%s}\n",
+ lock, lock->name);
+ else
+ printk(" [%p] {%s:%d}\n",
+ lock, lock->file, lock->line);
+
+ 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);
+ }
+}
+
+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");
+}
+
+void show_held_locks(struct task_struct *filter)
+{
+ struct thread_info *ti = current_thread_info();
+ 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_lock_irqsave(&debug_lock, flags, ti);
+ list_for_each(curr, &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_unlock_irqrestore(&debug_lock, flags, ti);
+
+ printk("\n#%03d: ", count);
+ printk_lock(lock, filter ? 0 : 1);
+ goto next;
+ }
+ debug_unlock_irqrestore(&debug_lock, flags, ti);
+ printk("\n");
+}
+
+void show_all_locks(void)
+{
+ struct task_struct *g, *p;
+ int count = 10;
+ int unlock = 1;
+
+ printk("\nshowing all tasks:\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 int check_deadlock(struct mutex *lock, int depth,
+ struct thread_info *ti, unsigned long ip)
+{
+ struct mutex *lockblk;
+ struct task_struct *task;
+
+ if (!debug_on)
+ return 0;
+
+ ti = lock->owner;
+ if (!ti)
+ return 0;
+ task = ti->task;
+ lockblk = NULL;
+ if (task->blocked_on)
+ lockblk = task->blocked_on->lock;
+ if (current == task) {
+ DEBUG_OFF();
+ if (depth)
+ return 1;
+ printk("\n==========================================\n");
+ printk( "[ BUG: lock recursion deadlock detected! |\n");
+ printk( "------------------------------------------\n");
+ printk("already locked: ");
+ printk_lock(lock, 1);
+ show_held_locks(task);
+ printk("-{current task's backtrace}----------------->\n");
+ dump_stack();
+ show_all_locks();
+ printk("[ turning off deadlock detection. Please report this trace. ]\n\n");
+ debug_local_irq_disable(ti);
+ 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");
+ goto print_it;
+ }
+ barrier();
+ if (lockblk && check_deadlock(lockblk, depth+1, ti, ip)) {
+ printk("\n============================================\n");
+ printk( "[ BUG: circular locking deadlock detected! ]\n");
+ printk( "--------------------------------------------\n");
+print_it:
+ printk("%s/%d is deadlocking current task %s/%d\n\n",
+ task->comm, task->pid, current->comm, current->pid);
+ printk("\n1) %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);
+
+ printk("\n2) %s/%d is blocked on this lock:\n",
+ task->comm, task->pid);
+ printk_lock(lockblk, 1);
+
+ show_held_locks(current);
+ 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();
+ show_all_locks();
+ printk("[ turning off deadlock detection. Please report this trace. ]\n\n");
+ debug_local_irq_disable(ti);
+ return 0;
+ }
+ return 0;
+}
+
+void check_no_held_locks(struct task_struct *task)
+{
+ struct list_head *curr, *next, *cursor = NULL;
+ struct thread_info *ti = task->thread_info;
+ struct thread_info *t;
+ unsigned long flags;
+ struct mutex *lock;
+
+restart:
+ if (!debug_on)
+ return;
+ debug_lock_irqsave(&debug_lock, flags, ti);
+ list_for_each_safe(curr, next, &held_locks) {
+ if (cursor && curr != cursor)
+ continue;
+ lock = list_entry(curr, struct mutex, held_list);
+ t = lock->owner;
+ if (t != task->thread_info)
+ continue;
+ cursor = next;
+ list_del_init(curr);
+ DEBUG_OFF();
+ debug_unlock_irqrestore(&debug_lock, flags, ti);
+
+ 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");
+ goto restart;
+ }
+ debug_unlock_irqrestore(&debug_lock, flags, ti);
+}
+
+int check_no_locks_freed(const void *from, const void *to)
+{
+ struct thread_info *ti = current_thread_info();
+ struct list_head *curr, *next, *cursor = NULL;
+ struct mutex *lock;
+ unsigned long flags;
+ void *lock_addr;
+ int err = 0;
+
+ if (!debug_on)
+ return err;
+restart:
+ debug_lock_irqsave(&debug_lock, flags, ti);
+ list_for_each_safe(curr, next, &held_locks) {
+ if (cursor && curr != cursor)
+ continue;
+ lock = list_entry(curr, struct mutex, held_list);
+ lock_addr = lock;
+ if (lock_addr < from || lock_addr >= to)
+ continue;
+ cursor = next;
+ list_del_init(curr);
+ DEBUG_OFF();
+ debug_unlock_irqrestore(&debug_lock, flags, ti);
+ err = 1;
+
+ 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");
+ goto restart;
+ }
+ debug_unlock_irqrestore(&debug_lock, flags, ti);
+
+ return err;
+}
+
+/*
+ * This must be called with lock->wait_lock held.
+ */
+static inline void
+debug_set_owner(struct mutex *lock, struct thread_info *new_owner __IP_DECL__)
+{
+ lock->owner = new_owner;
+ if (debug_on) {
+ DEBUG_WARN_ON(!list_empty(&lock->held_list));
+ list_add_tail(&lock->held_list, &held_locks);
+ lock->acquire_ip = ip;
+ }
+}
+
+/*
+ * Initialize/destruct the waiter structure, and poison it when debugging:
+ */
+static inline void debug_init_waiter(struct mutex_waiter *waiter)
+{
+ memset(waiter, 0x11, sizeof(*waiter));
+ waiter->magic = waiter;
+}
+
+static inline void debug_free_waiter(struct mutex_waiter *waiter)
+{
+ DEBUG_WARN_ON(!list_empty(&waiter->list));
+ memset(waiter, 0x22, sizeof(*waiter));
+}
Index: linux/lib/Kconfig.debug
===================================================================
--- linux.orig/lib/Kconfig.debug
+++ linux/lib/Kconfig.debug
@@ -95,6 +95,14 @@ config DEBUG_PREEMPT
if kernel code uses it in a preemption-unsafe way. Also, the kernel
will detect preemption count underflows.

+config DEBUG_MUTEXESS
+ bool "Mutex debugging, deadlock detection"
+ default y
+ depends on !DEBUG_MUTEX_NONE
+ help
+ This allows mutex semantics violations and mutex related deadlocks
+ (lockups) to be detected and reported automatically.
+
config DEBUG_SPINLOCK
bool "Spinlock debugging"
depends on DEBUG_KERNEL
-
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