2 files changed, 14 insertions, 3 deletions

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index a71158369fd4..e90e81ef6ab9 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -21,6 +21,7 @@ struct task_struct;
 struct exec_domain;
 #include <asm/processor.h>
 #include <asm/ftrace.h>
+#include <asm/atomic.h>
 
 struct thread_info {
         struct task_struct      *task;          /* main task structure */
@@ -45,6 +46,11 @@ struct thread_info {
         int             curr_ret_stack;
         /* Stack of return addresses for return function tracing */
         struct ftrace_ret_stack ret_stack[FTRACE_RET_STACK_SIZE];
+        /*
+         * Number of functions that haven't been traced
+         * because of depth overrun.
+         */
+        atomic_t        trace_overrun;
 #endif
 };
 
@@ -61,6 +67,7 @@ struct thread_info {
                 .fn = do_no_restart_syscall,    \
         },                                      \
         .curr_ret_stack = -1,\
+        .trace_overrun  = ATOMIC_INIT(0)        \
 }
 #else
 #define INIT_THREAD_INFO(tsk)                   \
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 924153edd973..356bb1eb6e9a 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -353,8 +353,10 @@ static int push_return_trace(unsigned long ret, unsigned long long time,
         struct thread_info *ti = current_thread_info();
 
         /* The return trace stack is full */
-        if (ti->curr_ret_stack == FTRACE_RET_STACK_SIZE - 1)
+        if (ti->curr_ret_stack == FTRACE_RET_STACK_SIZE - 1) {
+                atomic_inc(&ti->trace_overrun);
                 return -EBUSY;
+        }
 
         index = ++ti->curr_ret_stack;
         barrier();
@@ -367,7 +369,7 @@ static int push_return_trace(unsigned long ret, unsigned long long time,
 
 /* Retrieve a function return address to the trace stack on thread info.*/
 static void pop_return_trace(unsigned long *ret, unsigned long long *time,
-                                unsigned long *func)
+                                unsigned long *func, unsigned long *overrun)
 {
         int index;
 
@@ -376,6 +378,7 @@ static void pop_return_trace(unsigned long *ret, unsigned long long *time,
         *ret = ti->ret_stack[index].ret;
         *func = ti->ret_stack[index].func;
         *time = ti->ret_stack[index].calltime;
+        *overrun = atomic_read(&ti->trace_overrun);
         ti->curr_ret_stack--;
 }
 
@@ -386,7 +389,8 @@ static void pop_return_trace(unsigned long *ret, unsigned long long *time,
 unsigned long ftrace_return_to_handler(void)
 {
         struct ftrace_retfunc trace;
-        pop_return_trace(&trace.ret, &trace.calltime, &trace.func);
+        pop_return_trace(&trace.ret, &trace.calltime, &trace.func,
+                        &trace.overrun);
         trace.rettime = cpu_clock(raw_smp_processor_id());
         ftrace_function_return(&trace);