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Diffstat (limited to 'kernel/mutex-debug.c')
| -rw-r--r-- | kernel/mutex-debug.c | 464 |
1 files changed, 464 insertions, 0 deletions
diff --git a/kernel/mutex-debug.c b/kernel/mutex-debug.c new file mode 100644 index 00000000000..4fcb051a8b9 --- /dev/null +++ b/kernel/mutex-debug.c @@ -0,0 +1,464 @@ +/* + * kernel/mutex-debug.c + * + * Debugging code for mutexes + * + * Started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 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). + */ +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/delay.h> +#include <linux/module.h> +#include <linux/spinlock.h> +#include <linux/kallsyms.h> +#include <linux/interrupt.h> + +#include <asm/mutex.h> + +#include "mutex-debug.h" + +/* + * We need a global lock when we walk through the multi-process + * lock tree. Only used in the deadlock-debugging case. + */ +DEFINE_SPINLOCK(debug_mutex_lock); + +/* + * All locks held by all tasks, in a single global list: + */ +LIST_HEAD(debug_mutex_held_locks); + +/* + * In the debug case we carry the caller's instruction pointer into + * other functions, but we dont want the function argument overhead + * in the nondebug case - hence these macros: + */ +#define __IP_DECL__ , unsigned long ip +#define __IP__ , ip +#define __RET_IP__ , (unsigned long)__builtin_return_address(0) + +/* + * "mutex debugging enabled" 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(): + */ +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_lock_restore(&debug_mutex_lock, flags); + + printk("\n#%03d: ", count); + printk_lock(lock, filter ? 0 : 1); + goto next; + } + debug_spin_lock_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_lock_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_lock_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, const void *to) +{ + struct list_head *curr, *next; + 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_lock_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_lock_restore(&debug_mutex_lock, flags); +} + +/* + * Must be called with lock->wait_lock held. + */ +void debug_mutex_set_owner(struct mutex *lock, + struct thread_info *new_owner __IP_DECL__) +{ + lock->owner = new_owner; + DEBUG_WARN_ON(!list_empty(&lock->held_list)); + if (debug_mutex_on) { + list_add_tail(&lock->held_list, &debug_mutex_held_locks); + lock->acquire_ip = ip; + } +} + +void debug_mutex_init_waiter(struct mutex_waiter *waiter) +{ + memset(waiter, 0x11, sizeof(*waiter)); + waiter->magic = waiter; + INIT_LIST_HEAD(&waiter->list); +} + +void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter) +{ + SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock)); + DEBUG_WARN_ON(list_empty(&lock->wait_list)); + DEBUG_WARN_ON(waiter->magic != waiter); + DEBUG_WARN_ON(list_empty(&waiter->list)); +} + +void debug_mutex_free_waiter(struct mutex_waiter *waiter) +{ + DEBUG_WARN_ON(!list_empty(&waiter->list)); + memset(waiter, 0x22, sizeof(*waiter)); +} + +void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti __IP_DECL__) +{ + SMP_DEBUG_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; +} + +void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, + struct thread_info *ti) +{ + DEBUG_WARN_ON(list_empty(&waiter->list)); + DEBUG_WARN_ON(waiter->task != ti->task); + DEBUG_WARN_ON(ti->task->blocked_on != waiter); + ti->task->blocked_on = NULL; + + list_del_init(&waiter->list); + waiter->task = NULL; +} + +void debug_mutex_unlock(struct mutex *lock) +{ + DEBUG_WARN_ON(lock->magic != lock); + DEBUG_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next); + DEBUG_WARN_ON(lock->owner != current_thread_info()); + if (debug_mutex_on) { + DEBUG_WARN_ON(list_empty(&lock->held_list)); + list_del_init(&lock->held_list); + } +} + +void debug_mutex_init(struct mutex *lock, const char *name) +{ + /* + * Make sure we are not reinitializing a held lock: + */ + mutex_debug_check_no_locks_freed((void *)lock, (void *)(lock + 1)); + lock->owner = NULL; + INIT_LIST_HEAD(&lock->held_list); + lock->name = name; + lock->magic = lock; +} + +/*** + * mutex_destroy - mark a mutex unusable + * @lock: the mutex to be destroyed + * + * This function marks the mutex uninitialized, and any subsequent + * use of the mutex is forbidden. The mutex must not be locked when + * this function is called. + */ +void fastcall mutex_destroy(struct mutex *lock) +{ + DEBUG_WARN_ON(mutex_is_locked(lock)); + lock->magic = NULL; +} + +EXPORT_SYMBOL_GPL(mutex_destroy); + |