[PATCH] pi-futex: rt mutex debug
Runtime debugging functionality for rt-mutexes.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0ac2557..c41a129 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1034,6 +1034,7 @@
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
diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
index 12309c9..fa4a3b8 100644
--- a/include/linux/rtmutex.h
+++ b/include/linux/rtmutex.h
@@ -41,6 +41,19 @@
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__
# define rt_mutex_init(mutex) __rt_mutex_init(mutex, __FUNCTION__)
@@ -48,7 +61,7 @@
#else
# define __DEBUG_RT_MUTEX_INITIALIZER(mutexname)
# define rt_mutex_init(mutex) __rt_mutex_init(mutex, NULL)
-# define rt_mutex_debug_task_free(t) do { } while (0)
+# define rt_mutex_debug_task_free(t) do { } while (0)
#endif
#define __RT_MUTEX_INITIALIZER(mutexname) \
diff --git a/kernel/Makefile b/kernel/Makefile
index 21df9a3..f9c92d3 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -17,6 +17,7 @@
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
diff --git a/kernel/exit.c b/kernel/exit.c
index 304ef63..3e8a028 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -929,6 +929,7 @@
* 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();
diff --git a/kernel/rtmutex-debug.c b/kernel/rtmutex-debug.c
new file mode 100644
index 0000000..4aa8a2c9
--- /dev/null
+++ b/kernel/rtmutex-debug.c
@@ -0,0 +1,513 @@
+/*
+ * 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(¤t->pi_lock)) \
+ spin_unlock(¤t->pi_lock); \
+ if (spin_is_locked(¤t->held_list_lock)) \
+ spin_unlock(¤t->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(¤t->held_list_lock, flags);
+ list_for_each(curr, ¤t->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(¤t->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(¤t->held_list_lock, flags);
+ list_add_tail(&lock->held_list_entry, ¤t->held_list_head);
+ spin_unlock_irqrestore(¤t->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(¤t->held_list_lock, flags);
+ list_del_init(&lock->held_list_entry);
+ spin_unlock_irqrestore(¤t->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)
+{
+}
+
diff --git a/kernel/rtmutex-debug.h b/kernel/rtmutex-debug.h
new file mode 100644
index 0000000..7612fbc
--- /dev/null
+++ b/kernel/rtmutex-debug.h
@@ -0,0 +1,37 @@
+/*
+ * 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 file contains macros used solely by rtmutex.c. Debug version.
+ */
+
+#define __IP_DECL__ , unsigned long ip
+#define __IP__ , ip
+#define __RET_IP__ , (unsigned long)__builtin_return_address(0)
+
+extern void
+rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task);
+extern void rt_mutex_deadlock_account_unlock(struct task_struct *task);
+extern void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter);
+extern void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter);
+extern void debug_rt_mutex_init(struct rt_mutex *lock, const char *name);
+extern void debug_rt_mutex_lock(struct rt_mutex *lock __IP_DECL__);
+extern void debug_rt_mutex_unlock(struct rt_mutex *lock);
+extern void debug_rt_mutex_proxy_lock(struct rt_mutex *lock,
+ struct task_struct *powner __IP_DECL__);
+extern void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock);
+extern void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *waiter,
+ struct rt_mutex *lock);
+extern void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter);
+# define debug_rt_mutex_reset_waiter(w) \
+ do { (w)->deadlock_lock = NULL; } while (0)
+
+static inline int debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter,
+ int detect)
+{
+ return (waiter != NULL);
+}
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8bab010..06d3ea1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -107,6 +107,19 @@
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"
+ default y
+ depends on DEBUG_KERNEL && RT_MUTEXES
+ help
+ This allows rt mutex semantics violations and rt mutex related
+ deadlocks (lockups) to be detected and reported automatically.
+
+config DEBUG_PI_LIST
+ bool
+ default y
+ depends on DEBUG_RT_MUTEXES
+
config DEBUG_SPINLOCK
bool "Spinlock debugging"
depends on DEBUG_KERNEL
diff --git a/mm/slab.c b/mm/slab.c
index f378d02..233e39d 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -107,6 +107,7 @@
#include <linux/nodemask.h>
#include <linux/mempolicy.h>
#include <linux/mutex.h>
+#include <linux/rtmutex.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>