ftrace: stacktrace fix

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/ftrace.h

@@ -120,4 +120,12 @@ static inline void tracer_disable(void)
 # define trace_preempt_off(a0, a1)		do { } while (0)
 #endif
 
+#ifdef CONFIG_CONTEXT_SWITCH_TRACER
+extern void
+ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
+#else
+static inline void
+ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) { }
+#endif
+
 #endif /* _LINUX_FTRACE_H */

kernel/semaphore.c

@@ -31,6 +31,7 @@
 #include <linux/sched.h>
 #include <linux/semaphore.h>
 #include <linux/spinlock.h>
+#include <linux/ftrace.h>
 
 static noinline void __down(struct semaphore *sem);
 static noinline int __down_interruptible(struct semaphore *sem);
@@ -53,6 +54,7 @@ void down(struct semaphore *sem)
 {
 	unsigned long flags;
 
+	ftrace_special(sem->count, 0, __LINE__);
 	spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;

kernel/trace/trace.c

@@ -901,7 +901,7 @@ tracing_sched_switch_trace(struct trace_array *tr,
 	entry->ctx.next_pid	= next->pid;
 	entry->ctx.next_prio	= next->prio;
 	entry->ctx.next_state	= next->state;
-	__trace_stack(tr, data, flags, 4);
+	__trace_stack(tr, data, flags, 5);
 	__raw_spin_unlock(&data->lock);
 	raw_local_irq_restore(irq_flags);
 }
@@ -927,7 +927,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
 	entry->ctx.next_pid	= wakee->pid;
 	entry->ctx.next_prio	= wakee->prio;
 	entry->ctx.next_state	= wakee->state;
-	__trace_stack(tr, data, flags, 5);
+	__trace_stack(tr, data, flags, 6);
 	__raw_spin_unlock(&data->lock);
 	raw_local_irq_restore(irq_flags);
 

kernel/trace/trace.h

@@ -51,7 +51,7 @@ struct special_entry {
  * Stack-trace entry:
  */
 
-#define FTRACE_STACK_ENTRIES	5
+#define FTRACE_STACK_ENTRIES	8
 
 struct stack_entry {
 	unsigned long		caller[FTRACE_STACK_ENTRIES];