tracing/ftrace: Allow for instances to trigger their own stacktrace probes

Have the stacktrace function trigger probe trigger stack traces within the
instance that they were added to in the set_ftrace_filter.

 ># cd /sys/kernel/debug/tracing
 ># mkdir instances/foo
 ># cd instances/foo
 ># echo schedule:stacktrace:1 > set_ftrace_filter
 ># cat trace
 # tracer: nop
 #
 # entries-in-buffer/entries-written: 1/1   #P:4
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
           <idle>-0     [001] .N.2   202.585010: <stack trace>
  =>
  => schedule
  => schedule_preempt_disabled
  => do_idle
  => cpu_startup_entry
  => start_secondary
  => verify_cpu

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 14 insertions, 3 deletions

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 8c30ca733a5c..a3bddbfd0874 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -375,12 +375,23 @@ ftrace_traceoff(unsigned long ip, unsigned long parent_ip,
  */
 #define STACK_SKIP 4
 
+static __always_inline void trace_stack(struct trace_array *tr)
+{
+        unsigned long flags;
+        int pc;
+
+        local_save_flags(flags);
+        pc = preempt_count();
+
+        __trace_stack(tr, flags, STACK_SKIP, pc);
+}
+
 static void
 ftrace_stacktrace(unsigned long ip, unsigned long parent_ip,
                   struct trace_array *tr, struct ftrace_probe_ops *ops,
                   void *data)
 {
-        trace_dump_stack(STACK_SKIP);
+        trace_stack(tr);
 }
 
 static void
@@ -398,7 +409,7 @@ ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip,
 
         /* unlimited? */
         if (!mapper) {
-                trace_dump_stack(STACK_SKIP);
+                trace_stack(tr);
                 return;
         }
 
@@ -417,7 +428,7 @@ ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip,
                 new_count = old_count - 1;
                 new_count = cmpxchg(count, old_count, new_count);
                 if (new_count == old_count)
-                        trace_dump_stack(STACK_SKIP);
+                        trace_stack(tr);
 
                 if (!tracing_is_on())
                         return;