[PATCH] mutex subsystem, debugging code

mutex implementation - add debugging code.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>

include/linux/mutex-debug.h

+#ifndef __LINUX_MUTEX_DEBUG_H
+#define __LINUX_MUTEX_DEBUG_H
+
+/*
+ * Mutexes - debugging helpers:
+ */
+
+#define __DEBUG_MUTEX_INITIALIZER(lockname) \
+	, .held_list = LIST_HEAD_INIT(lockname.held_list), \
+	  .name = #lockname , .magic = &lockname
+
+#define mutex_init(sem)		__mutex_init(sem, __FUNCTION__)
+
+extern void FASTCALL(mutex_destroy(struct mutex *lock));
+
+extern void mutex_debug_show_all_locks(void);
+extern void mutex_debug_show_held_locks(struct task_struct *filter);
+extern void mutex_debug_check_no_locks_held(struct task_struct *task);
+extern void mutex_debug_check_no_locks_freed(const void *from, const void *to);
+
+#endif

include/linux/sched.h

@@ -817,6 +817,11 @@ struct task_struct {
 /* Protection of proc_dentry: nesting proc_lock, dcache_lock, write_lock_irq(&tasklist_lock); */
 	spinlock_t proc_lock;
 
+#ifdef CONFIG_DEBUG_MUTEXES
+	/* mutex deadlock detection */
+	struct mutex_waiter *blocked_on;
+#endif
+
 /* journalling filesystem info */
 	void *journal_info;
 

kernel/Makefile

@@ -9,6 +9,7 @@ obj-y     = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
 	    rcupdate.o intermodule.o extable.o params.o posix-timers.o \
 	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o
 
+obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o
 obj-$(CONFIG_FUTEX) += futex.o
 obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
 obj-$(CONFIG_SMP) += cpu.o spinlock.o

kernel/fork.c

@@ -979,6 +979,10 @@ static task_t *copy_process(unsigned long clone_flags,
  	}
 #endif
 
+#ifdef CONFIG_DEBUG_MUTEXES
+	p->blocked_on = NULL; /* not blocked yet */
+#endif
+
 	p->tgid = p->pid;
 	if (clone_flags & CLONE_THREAD)
 		p->tgid = current->tgid;

kernel/mutex-debug.h

+/*
+ * Mutexes: blocking mutual exclusion locks
+ *
+ * started by Ingo Molnar:
+ *
+ *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
+ *
+ * This file contains mutex debugging related internal declarations,
+ * prototypes and inline functions, for the CONFIG_DEBUG_MUTEXES case.
+ * More details are in kernel/mutex-debug.c.
+ */
+
+extern spinlock_t debug_mutex_lock;
+extern struct list_head debug_mutex_held_locks;
+extern int debug_mutex_on;
+
+/*
+ * 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)
+
+/*
+ * This must be called with lock->wait_lock held.
+ */
+extern void debug_mutex_set_owner(struct mutex *lock,
+				  struct thread_info *new_owner __IP_DECL__);
+
+static inline void debug_mutex_clear_owner(struct mutex *lock)
+{
+	lock->owner = NULL;
+}
+
+extern void debug_mutex_init_waiter(struct mutex_waiter *waiter);
+extern void debug_mutex_wake_waiter(struct mutex *lock,
+				    struct mutex_waiter *waiter);
+extern void debug_mutex_free_waiter(struct mutex_waiter *waiter);
+extern void debug_mutex_add_waiter(struct mutex *lock,
+				   struct mutex_waiter *waiter,
+				   struct thread_info *ti __IP_DECL__);
+extern void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
+				struct thread_info *ti);
+extern void debug_mutex_unlock(struct mutex *lock);
+extern void debug_mutex_init(struct mutex *lock, const char *name);
+
+#define debug_spin_lock(lock)				\
+	do {						\
+		local_irq_disable();			\
+		if (debug_mutex_on)			\
+			spin_lock(lock);		\
+	} while (0)
+
+#define debug_spin_unlock(lock)				\
+	do {						\
+		if (debug_mutex_on)			\
+			spin_unlock(lock);		\
+		local_irq_enable();			\
+		preempt_check_resched();		\
+	} while (0)
+
+#define debug_spin_lock_save(lock, flags)		\
+	do {						\
+		local_irq_save(flags);			\
+		if (debug_mutex_on)			\
+			spin_lock(lock);		\
+	} while (0)
+
+#define debug_spin_lock_restore(lock, flags)		\
+	do {						\
+		if (debug_mutex_on)			\
+			spin_unlock(lock);		\
+		local_irq_restore(flags);		\
+		preempt_check_resched();		\
+	} while (0)
+
+#define spin_lock_mutex(lock)				\
+	do {						\
+		struct mutex *l = container_of(lock, struct mutex, wait_lock); \
+							\
+		DEBUG_WARN_ON(in_interrupt());		\
+		debug_spin_lock(&debug_mutex_lock);	\
+		spin_lock(lock);			\
+		DEBUG_WARN_ON(l->magic != l);		\
+	} while (0)
+
+#define spin_unlock_mutex(lock)				\
+	do {						\
+		spin_unlock(lock);			\
+		debug_spin_unlock(&debug_mutex_lock);	\
+	} while (0)
+
+#define DEBUG_OFF()					\
+do {							\
+	if (debug_mutex_on) {				\
+		debug_mutex_on = 0;			\
+		console_verbose();			\
+		if (spin_is_locked(&debug_mutex_lock))	\
+			spin_unlock(&debug_mutex_lock);	\
+	}						\
+} while (0)
+
+#define DEBUG_BUG()					\
+do {							\
+	if (debug_mutex_on) {				\
+		DEBUG_OFF();				\
+		BUG();					\
+	}						\
+} while (0)
+
+#define DEBUG_WARN_ON(c)				\
+do {							\
+	if (unlikely(c && debug_mutex_on)) {		\
+		DEBUG_OFF();				\
+		WARN_ON(1);				\
+	}						\
+} while (0)
+
+# define DEBUG_BUG_ON(c)				\
+do {							\
+	if (unlikely(c))				\
+		DEBUG_BUG();				\
+} while (0)
+
+#ifdef CONFIG_SMP
+# define SMP_DEBUG_WARN_ON(c)			DEBUG_WARN_ON(c)
+# define SMP_DEBUG_BUG_ON(c)			DEBUG_BUG_ON(c)
+#else
+# define SMP_DEBUG_WARN_ON(c)			do { } while (0)
+# define SMP_DEBUG_BUG_ON(c)			do { } while (0)
+#endif
+

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_MUTEXES
+	bool "Mutex debugging, deadlock detection"
+	default y
+	depends on DEBUG_KERNEL
+	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