1 files changed, 33 insertions, 35 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f62768288592..53e8ccbae818 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -431,23 +431,8 @@ struct tracer {
  *  When function tracing occurs, the following steps are made:
  *   If arch does not support a ftrace feature:
  *    call internal function (uses INTERNAL bits) which calls...
- *   If callback is registered to the "global" list, the list
- *    function is called and recursion checks the GLOBAL bits.
- *    then this function calls...
  *   The function callback, which can use the FTRACE bits to
  *    check for recursion.
- *
- * Now if the arch does not suppport a feature, and it calls
- * the global list function which calls the ftrace callback
- * all three of these steps will do a recursion protection.
- * There's no reason to do one if the previous caller already
- * did. The recursion that we are protecting against will
- * go through the same steps again.
- *
- * To prevent the multiple recursion checks, if a recursion
- * bit is set that is higher than the MAX bit of the current
- * check, then we know that the check was made by the previous
- * caller, and we can skip the current check.
  */
 enum {
 	TRACE_BUFFER_BIT,
@@ -460,12 +445,14 @@ enum {
 	TRACE_FTRACE_NMI_BIT,
 	TRACE_FTRACE_IRQ_BIT,
 	TRACE_FTRACE_SIRQ_BIT,
+	TRACE_FTRACE_TRANSITION_BIT,
 
-	/* INTERNAL_BITs must be greater than FTRACE_BITs */
+	/* Internal use recursion bits */
 	TRACE_INTERNAL_BIT,
 	TRACE_INTERNAL_NMI_BIT,
 	TRACE_INTERNAL_IRQ_BIT,
 	TRACE_INTERNAL_SIRQ_BIT,
+	TRACE_INTERNAL_TRANSITION_BIT,
 
 	TRACE_CONTROL_BIT,
 
@@ -487,12 +474,18 @@ enum {
 #define TRACE_CONTEXT_BITS	4
 
 #define TRACE_FTRACE_START	TRACE_FTRACE_BIT
-#define TRACE_FTRACE_MAX	((1 << (TRACE_FTRACE_START + TRACE_CONTEXT_BITS)) - 1)
 
 #define TRACE_LIST_START	TRACE_INTERNAL_BIT
-#define TRACE_LIST_MAX		((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1)
 
-#define TRACE_CONTEXT_MASK	TRACE_LIST_MAX
+#define TRACE_CONTEXT_MASK	((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1)
+
+enum {
+	TRACE_CTX_NMI,
+	TRACE_CTX_IRQ,
+	TRACE_CTX_SOFTIRQ,
+	TRACE_CTX_NORMAL,
+	TRACE_CTX_TRANSITION,
+};
 
 static __always_inline int trace_get_context_bit(void)
 {
@@ -500,30 +493,36 @@ static __always_inline int trace_get_context_bit(void)
 
 	if (in_interrupt()) {
 		if (in_nmi())
-			bit = 0;
+			bit = TRACE_CTX_NMI;
 
 		else if (in_irq())
-			bit = 1;
+			bit = TRACE_CTX_IRQ;
 		else
-			bit = 2;
+			bit = TRACE_CTX_SOFTIRQ;
 	} else
-		bit = 3;
+		bit = TRACE_CTX_NORMAL;
 
 	return bit;
 }
 
-static __always_inline int trace_test_and_set_recursion(int start, int max)
+static __always_inline int trace_test_and_set_recursion(int start)
 {
 	unsigned int val = current->trace_recursion;
 	int bit;
 
-	/* A previous recursion check was made */
-	if ((val & TRACE_CONTEXT_MASK) > 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 = start + TRACE_CTX_TRANSITION;
+		if (trace_recursion_test(bit))
+			return -1;
+		trace_recursion_set(bit);
+		barrier();
+		return bit;
+	}
 
 	val |= 1 << bit;
 	current->trace_recursion = val;
@@ -536,9 +535,6 @@ static __always_inline void trace_clear_recursion(int bit)
 {
 	unsigned int val = current->trace_recursion;
 
-	if (!bit)
-		return;
-
 	bit = 1 << bit;
 	val &= ~bit;
 
@@ -636,13 +632,15 @@ 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)
 {
 }