Merge branch 'tip/perf/urgent-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into perf/urgent

1 files changed, 19 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 82d9b8106cd0..ee6a7339cf0e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1284,6 +1284,8 @@ void trace_dump_stack(void)
         __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count());
 }
 
+static DEFINE_PER_CPU(int, user_stack_count);
+
 void
 ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
 {
@@ -1302,6 +1304,18 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
         if (unlikely(in_nmi()))
                 return;
 
+        /*
+         * prevent recursion, since the user stack tracing may
+         * trigger other kernel events.
+         */
+        preempt_disable();
+        if (__this_cpu_read(user_stack_count))
+                goto out;
+
+        __this_cpu_inc(user_stack_count);
+
+
+
         event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,
                                           sizeof(*entry), flags, pc);
         if (!event)
@@ -1319,6 +1333,11 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc)
         save_stack_trace_user(&trace);
         if (!filter_check_discard(call, entry, buffer, event))
                 ring_buffer_unlock_commit(buffer, event);
+
+        __this_cpu_dec(user_stack_count);
+
+ out:
+        preempt_enable();
 }
 
 #ifdef UNUSED