Merge tag 'v4.4.274' into toradex_vf_4.4-next

Linux 4.4.274

1 files changed, 27 insertions, 5 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 12a82a7ad5a6..7150892c692a 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -478,6 +478,12 @@ enum {
  * can only be modified by current, we can reuse trace_recursion.
  */
 	TRACE_IRQ_BIT,
+
+	/*
+	 * When transitioning between context, the preempt_count() may
+	 * not be correct. Allow for a single recursion to cover this case.
+	 */
+	TRACE_TRANSITION_BIT,
 };
 
 #define trace_recursion_set(bit)	do { (current)->trace_recursion |= (1<<(bit)); } while (0)
@@ -522,14 +528,27 @@ static __always_inline int trace_test_and_set_recursion(int start, int max)
 		return 0;
 
 	bit = trace_get_context_bit() + start;
-	if (unlikely(val & (1 << bit)))
-		return -1;
+	if (unlikely(val & (1 << bit))) {
+		/*
+		 * It could be that preempt_count has not been updated during
+		 * a switch between contexts. Allow for a single recursion.
+		 */
+		bit = TRACE_TRANSITION_BIT;
+		if (trace_recursion_test(bit))
+			return -1;
+		trace_recursion_set(bit);
+		barrier();
+		return bit + 1;
+	}
+
+	/* Normal check passed, clear the transition to allow it again */
+	trace_recursion_clear(TRACE_TRANSITION_BIT);
 
 	val |= 1 << bit;
 	current->trace_recursion = val;
 	barrier();
 
-	return bit;
+	return bit + 1;
 }
 
 static __always_inline void trace_clear_recursion(int bit)
@@ -539,6 +558,7 @@ static __always_inline void trace_clear_recursion(int bit)
 	if (!bit)
 		return;
 
+	bit--;
 	bit = 1 << bit;
 	val &= ~bit;
 
@@ -636,13 +656,15 @@ void update_max_tr_single(struct trace_array *tr,
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
 #ifdef CONFIG_STACKTRACE
-void ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags,
+void ftrace_trace_userstack(struct trace_array *tr,
+			    struct ring_buffer *buffer, unsigned long flags,
 			    int pc);
 
 void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
 		   int pc);
 #else
-static inline void ftrace_trace_userstack(struct ring_buffer *buffer,
+static inline void ftrace_trace_userstack(struct trace_array *tr,
+					  struct ring_buffer *buffer,
 					  unsigned long flags, int pc)
 {
 }