[PATCH] pi-futex: rt mutex debug (e7eebaf6) · Commits · git / linux-net

include/linux/mm.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -1034,6 +1034,7 @@ static inline void
		debug_check_no_locks_freed(const void *from, unsigned long len)
		{
		mutex_debug_check_no_locks_freed(from, len);
		rt_mutex_debug_check_no_locks_freed(from, len);
		}

		#ifndef CONFIG_DEBUG_PAGEALLOC

include/linux/rtmutex.h

+14 −1

Original line number	Diff line number	Diff line
		@@ -40,6 +40,19 @@ struct rt_mutex {
		struct rt_mutex_waiter;
		struct hrtimer_sleeper;

		#ifdef CONFIG_DEBUG_RT_MUTEXES
		extern int rt_mutex_debug_check_no_locks_freed(const void *from,
		unsigned long len);
		extern void rt_mutex_debug_check_no_locks_held(struct task_struct *task);
		#else
		static inline int rt_mutex_debug_check_no_locks_freed(const void *from,
		unsigned long len)
		{
		return 0;
		}
		# define rt_mutex_debug_check_no_locks_held(task) do { } while (0)
		#endif

		#ifdef CONFIG_DEBUG_RT_MUTEXES
		# define __DEBUG_RT_MUTEX_INITIALIZER(mutexname) \
		, .name = #mutexname, .file = __FILE__, .line = __LINE__

kernel/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@ ifeq ($(CONFIG_COMPAT),y)
		obj-$(CONFIG_FUTEX) += futex_compat.o
		endif
		obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
		obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
		obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
		obj-$(CONFIG_SMP) += cpu.o spinlock.o
		obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o

kernel/exit.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -929,6 +929,7 @@ fastcall NORET_TYPE void do_exit(long code)
		* If DEBUG_MUTEXES is on, make sure we are holding no locks:
		*/
		mutex_debug_check_no_locks_held(tsk);
		rt_mutex_debug_check_no_locks_held(tsk);

		if (tsk->io_context)
		exit_io_context();

kernel/rtmutex-debug.c

0 → 100644

+513 −0

Original line number	Diff line number	Diff line
		/*
		* RT-Mutexes: blocking mutual exclusion locks with PI support
		*
		* started by Ingo Molnar and Thomas Gleixner:
		*
		* Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
		* Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
		*
		* This code is based on the rt.c implementation in the preempt-rt tree.
		* Portions of said code are
		*
		* Copyright (C) 2004 LynuxWorks, Inc., Igor Manyilov, Bill Huey
		* Copyright (C) 2006 Esben Nielsen
		* Copyright (C) 2006 Kihon Technologies Inc.,
		* Steven Rostedt <rostedt@goodmis.org>
		*
		* See rt.c in preempt-rt for proper credits and further information
		*/
		#include <linux/config.h>
		#include <linux/sched.h>
		#include <linux/delay.h>
		#include <linux/module.h>
		#include <linux/spinlock.h>
		#include <linux/kallsyms.h>
		#include <linux/syscalls.h>
		#include <linux/interrupt.h>
		#include <linux/plist.h>
		#include <linux/fs.h>

		#include "rtmutex_common.h"

		#ifdef CONFIG_DEBUG_RT_MUTEXES
		# include "rtmutex-debug.h"
		#else
		# include "rtmutex.h"
		#endif

		# define TRACE_WARN_ON(x) WARN_ON(x)
		# define TRACE_BUG_ON(x) BUG_ON(x)

		# define TRACE_OFF() \
		do { \
		if (rt_trace_on) { \
		rt_trace_on = 0; \
		console_verbose(); \
		if (spin_is_locked(&current->pi_lock)) \
		spin_unlock(&current->pi_lock); \
		if (spin_is_locked(&current->held_list_lock)) \
		spin_unlock(&current->held_list_lock); \
		} \
		} while (0)

		# define TRACE_OFF_NOLOCK() \
		do { \
		if (rt_trace_on) { \
		rt_trace_on = 0; \
		console_verbose(); \
		} \
		} while (0)

		# define TRACE_BUG_LOCKED() \
		do { \
		TRACE_OFF(); \
		BUG(); \
		} while (0)

		# define TRACE_WARN_ON_LOCKED(c) \
		do { \
		if (unlikely(c)) { \
		TRACE_OFF(); \
		WARN_ON(1); \
		} \
		} while (0)

		# define TRACE_BUG_ON_LOCKED(c) \
		do { \
		if (unlikely(c)) \
		TRACE_BUG_LOCKED(); \
		} while (0)

		#ifdef CONFIG_SMP
		# define SMP_TRACE_BUG_ON_LOCKED(c) TRACE_BUG_ON_LOCKED(c)
		#else
		# define SMP_TRACE_BUG_ON_LOCKED(c) do { } while (0)
		#endif

		/*
		* 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():
		*/
		int rt_trace_on = 1;

		void deadlock_trace_off(void)
		{
		rt_trace_on = 0;
		}

		static void printk_task(task_t *p)
		{
		if (p)
		printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio);
		else
		printk("<none>");
		}

		static void printk_task_short(task_t *p)
		{
		if (p)
		printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio);
		else
		printk("<none>");
		}

		static void printk_lock(struct rt_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 && rt_mutex_owner(lock)) {
		printk(".. ->owner: %p\n", lock->owner);
		printk(".. held by: ");
		printk_task(rt_mutex_owner(lock));
		printk("\n");
		}
		if (rt_mutex_owner(lock)) {
		printk("... acquired at: ");
		print_symbol("%s\n", lock->acquire_ip);
		}
		}

		static void printk_waiter(struct rt_mutex_waiter *w)
		{
		printk("-------------------------\n");
		printk("\| waiter struct %p:\n", w);
		printk("\| w->list_entry: [DP:%p/%p\|SP:%p/%p\|PRI:%d]\n",
		w->list_entry.plist.prio_list.prev, w->list_entry.plist.prio_list.next,
		w->list_entry.plist.node_list.prev, w->list_entry.plist.node_list.next,
		w->list_entry.prio);
		printk("\| w->pi_list_entry: [DP:%p/%p\|SP:%p/%p\|PRI:%d]\n",
		w->pi_list_entry.plist.prio_list.prev, w->pi_list_entry.plist.prio_list.next,
		w->pi_list_entry.plist.node_list.prev, w->pi_list_entry.plist.node_list.next,
		w->pi_list_entry.prio);
		printk("\n\| lock:\n");
		printk_lock(w->lock, 1);
		printk("\| w->ti->task:\n");
		printk_task(w->task);
		printk("\| blocked at: ");
		print_symbol("%s\n", w->ip);
		printk("-------------------------\n");
		}

		static void show_task_locks(task_t *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->pi_blocked_on) {
		struct rt_mutex *lock = p->pi_blocked_on->lock;

		printk(" blocked on:");
		printk_lock(lock, 1);
		} else
		printk(" (not blocked)\n");
		}

		void rt_mutex_show_held_locks(task_t *task, int verbose)
		{
		struct list_head curr, cursor = NULL;
		struct rt_mutex *lock;
		task_t *t;
		unsigned long flags;
		int count = 0;

		if (!rt_trace_on)
		return;

		if (verbose) {
		printk("------------------------------\n");
		printk("\| showing all locks held by: \| (");
		printk_task_short(task);
		printk("):\n");
		printk("------------------------------\n");
		}

		next:
		spin_lock_irqsave(&task->held_list_lock, flags);
		list_for_each(curr, &task->held_list_head) {
		if (cursor && curr != cursor)
		continue;
		lock = list_entry(curr, struct rt_mutex, held_list_entry);
		t = rt_mutex_owner(lock);
		WARN_ON(t != task);
		count++;
		cursor = curr->next;
		spin_unlock_irqrestore(&task->held_list_lock, flags);

		printk("\n#%03d: ", count);
		printk_lock(lock, 0);
		goto next;
		}
		spin_unlock_irqrestore(&task->held_list_lock, flags);

		printk("\n");
		}

		void rt_mutex_show_all_locks(void)
		{
		task_t g, p;
		int count = 10;
		int unlock = 1;

		printk("\n");
		printk("----------------------\n");
		printk("\| showing all tasks: \|\n");
		printk("----------------------\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");

		printk("-----------------------------------------\n");
		printk("\| showing all locks held in the system: \|\n");
		printk("-----------------------------------------\n");

		do_each_thread(g, p) {
		rt_mutex_show_held_locks(p, 0);
		if (!unlock)
		if (read_trylock(&tasklist_lock))
		unlock = 1;
		} while_each_thread(g, p);


		printk("=============================================\n\n");

		if (unlock)
		read_unlock(&tasklist_lock);
		}

		void rt_mutex_debug_check_no_locks_held(task_t *task)
		{
		struct rt_mutex_waiter *w;
		struct list_head *curr;
		struct rt_mutex *lock;

		if (!rt_trace_on)
		return;
		if (!rt_prio(task->normal_prio) && rt_prio(task->prio)) {
		printk("BUG: PI priority boost leaked!\n");
		printk_task(task);
		printk("\n");
		}
		if (list_empty(&task->held_list_head))
		return;

		spin_lock(&task->pi_lock);
		plist_for_each_entry(w, &task->pi_waiters, pi_list_entry) {
		TRACE_OFF();

		printk("hm, PI interest held at exit time? Task:\n");
		printk_task(task);
		printk_waiter(w);
		return;
		}
		spin_unlock(&task->pi_lock);

		list_for_each(curr, &task->held_list_head) {
		lock = list_entry(curr, struct rt_mutex, held_list_entry);

		printk("BUG: %s/%d, lock held at task exit time!\n",
		task->comm, task->pid);
		printk_lock(lock, 1);
		if (rt_mutex_owner(lock) != task)
		printk("exiting task is not even the owner??\n");
		}
		}

		int rt_mutex_debug_check_no_locks_freed(const void *from, unsigned long len)
		{
		const void *to = from + len;
		struct list_head *curr;
		struct rt_mutex *lock;
		unsigned long flags;
		void *lock_addr;

		if (!rt_trace_on)
		return 0;

		spin_lock_irqsave(&current->held_list_lock, flags);
		list_for_each(curr, &current->held_list_head) {
		lock = list_entry(curr, struct rt_mutex, held_list_entry);
		lock_addr = lock;
		if (lock_addr < from \|\| lock_addr >= to)
		continue;
		TRACE_OFF();

		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 (rt_mutex_owner(lock) != current)
		printk("freeing task is not even the owner??\n");
		return 1;
		}
		spin_unlock_irqrestore(&current->held_list_lock, flags);

		return 0;
		}

		void rt_mutex_debug_task_free(struct task_struct *task)
		{
		WARN_ON(!plist_head_empty(&task->pi_waiters));
		WARN_ON(task->pi_blocked_on);
		}

		/*
		* We fill out the fields in the waiter to store the information about
		* the deadlock. We print when we return. act_waiter can be NULL in
		* case of a remove waiter operation.
		*/
		void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter,
		struct rt_mutex *lock)
		{
		struct task_struct *task;

		if (!rt_trace_on \|\| detect \|\| !act_waiter)
		return;

		task = rt_mutex_owner(act_waiter->lock);
		if (task && task != current) {
		act_waiter->deadlock_task_pid = task->pid;
		act_waiter->deadlock_lock = lock;
		}
		}

		void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
		{
		struct task_struct *task;

		if (!waiter->deadlock_lock \|\| !rt_trace_on)
		return;

		task = find_task_by_pid(waiter->deadlock_task_pid);
		if (!task)
		return;

		TRACE_OFF_NOLOCK();

		printk("\n============================================\n");
		printk( "[ BUG: circular locking deadlock detected! ]\n");
		printk( "--------------------------------------------\n");
		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(waiter->lock, 1);

		printk("... trying at: ");
		print_symbol("%s\n", waiter->ip);

		printk("\n2) %s/%d is blocked on this lock:\n", task->comm, task->pid);
		printk_lock(waiter->deadlock_lock, 1);

		rt_mutex_show_held_locks(current, 1);
		rt_mutex_show_held_locks(task, 1);

		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();
		rt_mutex_show_all_locks();
		printk("[ turning off deadlock detection."
		"Please report this trace. ]\n\n");
		local_irq_disable();
		}

		void debug_rt_mutex_lock(struct rt_mutex *lock __IP_DECL__)
		{
		unsigned long flags;

		if (rt_trace_on) {
		TRACE_WARN_ON_LOCKED(!list_empty(&lock->held_list_entry));

		spin_lock_irqsave(&current->held_list_lock, flags);
		list_add_tail(&lock->held_list_entry, &current->held_list_head);
		spin_unlock_irqrestore(&current->held_list_lock, flags);

		lock->acquire_ip = ip;
		}
		}

		void debug_rt_mutex_unlock(struct rt_mutex *lock)
		{
		unsigned long flags;

		if (rt_trace_on) {
		TRACE_WARN_ON_LOCKED(rt_mutex_owner(lock) != current);
		TRACE_WARN_ON_LOCKED(list_empty(&lock->held_list_entry));

		spin_lock_irqsave(&current->held_list_lock, flags);
		list_del_init(&lock->held_list_entry);
		spin_unlock_irqrestore(&current->held_list_lock, flags);
		}
		}

		void debug_rt_mutex_proxy_lock(struct rt_mutex *lock,
		struct task_struct *powner __IP_DECL__)
		{
		unsigned long flags;

		if (rt_trace_on) {
		TRACE_WARN_ON_LOCKED(!list_empty(&lock->held_list_entry));

		spin_lock_irqsave(&powner->held_list_lock, flags);
		list_add_tail(&lock->held_list_entry, &powner->held_list_head);
		spin_unlock_irqrestore(&powner->held_list_lock, flags);

		lock->acquire_ip = ip;
		}
		}

		void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
		{
		unsigned long flags;

		if (rt_trace_on) {
		struct task_struct *owner = rt_mutex_owner(lock);

		TRACE_WARN_ON_LOCKED(!owner);
		TRACE_WARN_ON_LOCKED(list_empty(&lock->held_list_entry));

		spin_lock_irqsave(&owner->held_list_lock, flags);
		list_del_init(&lock->held_list_entry);
		spin_unlock_irqrestore(&owner->held_list_lock, flags);
		}
		}

		void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
		{
		memset(waiter, 0x11, sizeof(*waiter));
		plist_node_init(&waiter->list_entry, MAX_PRIO);
		plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
		}

		void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
		{
		TRACE_WARN_ON(!plist_node_empty(&waiter->list_entry));
		TRACE_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
		TRACE_WARN_ON(waiter->task);
		memset(waiter, 0x22, sizeof(*waiter));
		}

		void debug_rt_mutex_init(struct rt_mutex lock, const char name)
		{
		void *addr = lock;

		if (rt_trace_on) {
		rt_mutex_debug_check_no_locks_freed(addr,
		sizeof(struct rt_mutex));
		INIT_LIST_HEAD(&lock->held_list_entry);
		lock->name = name;
		}
		}

		void rt_mutex_deadlock_account_lock(struct rt_mutex lock, task_t task)
		{
		}

		void rt_mutex_deadlock_account_unlock(struct task_struct *task)
		{
		}