sched: Add lock_count to task struct

Debugging interface.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/sched.h

@@ -1395,6 +1395,26 @@ struct task_struct {
 	gfp_t lockdep_reclaim_gfp;
 #endif
 
+/* realtime bits */
+
+#define MAX_PREEMPT_TRACE 25
+#define MAX_LOCK_STACK	MAX_PREEMPT_TRACE
+#ifdef CONFIG_DEBUG_PREEMPT
+	int lock_count;
+# ifdef CONFIG_PREEMPT_RT
+	struct rt_mutex *owned_lock[MAX_LOCK_STACK];
+# endif
+#endif
+#ifdef CONFIG_DETECT_SOFTLOCKUP
+	unsigned long	softlockup_count; /* Count to keep track how long the
+					   *  thread is in the kernel without
+					   *  sleeping.
+					   */
+#endif
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+	void *last_kernel_lock;
+#endif
+
 /* journalling filesystem info */
 	void *journal_info;
 

kernel/fork.c

@@ -911,6 +911,9 @@ static void rt_mutex_init_task(struct task_struct *p)
 #ifdef CONFIG_RT_MUTEXES
 	plist_head_init_atomic(&p->pi_waiters, &p->pi_lock);
 	p->pi_blocked_on = NULL;
+# ifdef CONFIG_DEBUG_RT_MUTEXES
+	p->last_kernel_lock = NULL;
+# endif
 #endif
 }
 
@@ -1123,6 +1126,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
 	if (retval)
 		goto bad_fork_cleanup_io;
+#ifdef CONFIG_DEBUG_PREEMPT
+	p->lock_count = 0;
+#endif
 
 	if (pid != &init_struct_pid) {
 		retval = -ENOMEM;