4 files changed, 53 insertions, 1 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 97c83e1bc589..39b95c56587e 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -488,8 +488,15 @@ static inline int test_tsk_trace_graph(struct task_struct *tsk)
 
 extern int ftrace_dump_on_oops;
 
+#ifdef CONFIG_PREEMPT
+#define INIT_TRACE_RECURSION            .trace_recursion = 0,
+#endif
+
 #endif /* CONFIG_TRACING */
 
+#ifndef INIT_TRACE_RECURSION
+#define INIT_TRACE_RECURSION
+#endif
 
 #ifdef CONFIG_HW_BRANCH_TRACER
 
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index dcfb93337e9a..6fc218529863 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -187,6 +187,7 @@ extern struct cred init_cred;
         INIT_TRACE_IRQFLAGS                                             \
         INIT_LOCKDEP                                                    \
         INIT_FTRACE_GRAPH                                               \
+        INIT_TRACE_RECURSION                                            \
 }
 
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b4c38bc8049c..7ede5e490913 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1428,7 +1428,9 @@ struct task_struct {
 #ifdef CONFIG_TRACING
         /* state flags for use by tracers */
         unsigned long trace;
-#endif
+        /* bitmask of trace recursion */
+        unsigned long trace_recursion;
+#endif /* CONFIG_TRACING */
 };
 
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 84a6055f37c9..b421b0ea9112 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1481,6 +1481,40 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
         return event;
 }
 
+static int trace_irq_level(void)
+{
+        return hardirq_count() + softirq_count() + in_nmi();
+}
+
+static int trace_recursive_lock(void)
+{
+        int level;
+
+        level = trace_irq_level();
+
+        if (unlikely(current->trace_recursion & (1 << level))) {
+                /* Disable all tracing before we do anything else */
+                tracing_off_permanent();
+                WARN_ON_ONCE(1);
+                return -1;
+        }
+
+        current->trace_recursion |= 1 << level;
+
+        return 0;
+}
+
+static void trace_recursive_unlock(void)
+{
+        int level;
+
+        level = trace_irq_level();
+
+        WARN_ON_ONCE(!current->trace_recursion & (1 << level));
+
+        current->trace_recursion &= ~(1 << level);
+}
+
 static DEFINE_PER_CPU(int, rb_need_resched);
 
 /**
@@ -1514,6 +1548,9 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
         /* If we are tracing schedule, we don't want to recurse */
         resched = ftrace_preempt_disable();
 
+        if (trace_recursive_lock())
+                goto out_nocheck;
+
         cpu = raw_smp_processor_id();
 
         if (!cpumask_test_cpu(cpu, buffer->cpumask))
@@ -1543,6 +1580,9 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
         return event;
 
  out:
+        trace_recursive_unlock();
+
+ out_nocheck:
         ftrace_preempt_enable(resched);
         return NULL;
 }
@@ -1581,6 +1621,8 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer,
 
         rb_commit(cpu_buffer, event);
 
+        trace_recursive_unlock();
+
         /*
          * Only the last preempt count needs to restore preemption.
          */