tracing: Make sure RCU is watching before calling a stack trace

[sfrench/cifs-2.6.git] / kernel / trace / trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c4536c4490217a2e6b59e423c70c0f1836a34a9d..1122f151466f64425089b9b9ecbd4b1a7584ba8a 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1558,7 +1558,7 @@ static __init int init_trace_selftests(void)
 
        return 0;
 }
-early_initcall(init_trace_selftests);
+core_initcall(init_trace_selftests);
 #else
 static inline int run_tracer_selftest(struct tracer *type)
 {
@@ -2568,7 +2568,36 @@ static inline void ftrace_trace_stack(struct trace_array *tr,
 void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
                   int pc)
 {
-       __ftrace_trace_stack(tr->trace_buffer.buffer, flags, skip, pc, NULL);
+       struct ring_buffer *buffer = tr->trace_buffer.buffer;
+
+       if (rcu_is_watching()) {
+               __ftrace_trace_stack(buffer, flags, skip, pc, NULL);
+               return;
+       }
+
+       /*
+        * When an NMI triggers, RCU is enabled via rcu_nmi_enter(),
+        * but if the above rcu_is_watching() failed, then the NMI
+        * triggered someplace critical, and rcu_irq_enter() should
+        * not be called from NMI.
+        */
+       if (unlikely(in_nmi()))
+               return;
+
+       /*
+        * It is possible that a function is being traced in a
+        * location that RCU is not watching. A call to
+        * rcu_irq_enter() will make sure that it is, but there's
+        * a few internal rcu functions that could be traced
+        * where that wont work either. In those cases, we just
+        * do nothing.
+        */
+       if (unlikely(rcu_irq_enter_disabled()))
+               return;
+
+       rcu_irq_enter_irqson();
+       __ftrace_trace_stack(buffer, flags, skip, pc, NULL);
+       rcu_irq_exit_irqson();
 }
 
 /**
@@ -7550,6 +7579,7 @@ static int instance_rmdir(const char *name)
        }
 
        tracing_set_nop(tr);
+       clear_ftrace_function_probes(tr);
        event_trace_del_tracer(tr);
        ftrace_clear_pids(tr);
        ftrace_destroy_function_files(tr);