fgraph: Have set_graph_notrace only affect function_graph tracer

In order to make the function graph infrastructure more generic, there can
not be code specific for the function_graph tracer in the generic code. This
includes the set_graph_notrace logic, that stops all graph calls when a
function in the set_graph_notrace is hit.

By using the trace_recursion mask, we can use a bit in the current
task_struct to implement the notrace code, and move the logic out of
fgraph.c and into trace_functions_graph.c and keeps it affecting only the
tracer and not all call graph callbacks.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 5ad9c0e..e852b69 100644 (file)
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -64,30 +64,9 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func,
                return -EBUSY;
        }
 
-       /*
-        * The curr_ret_stack is an index to ftrace return stack of
-        * current task.  Its value should be in [0, FTRACE_RETFUNC_
-        * DEPTH) when the function graph tracer is used.  To support
-        * filtering out specific functions, it makes the index
-        * negative by subtracting huge value (FTRACE_NOTRACE_DEPTH)
-        * so when it sees a negative index the ftrace will ignore
-        * the record.  And the index gets recovered when returning
-        * from the filtered function by adding the FTRACE_NOTRACE_
-        * DEPTH and then it'll continue to record functions normally.
-        *
-        * The curr_ret_stack is initialized to -1 and get increased
-        * in this function.  So it can be less than -1 only if it was
-        * filtered out via ftrace_graph_notrace_addr() which can be
-        * set from set_graph_notrace file in tracefs by user.
-        */
-       if (current->curr_ret_stack < -1)
-               return -EBUSY;
-
        calltime = trace_clock_local();
 
        index = ++current->curr_ret_stack;
-       if (ftrace_graph_notrace_addr(func))
-               current->curr_ret_stack -= FTRACE_NOTRACE_DEPTH;
        barrier();
        current->ret_stack[index].ret = ret;
        current->ret_stack[index].func = func;

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 447bd96..f67060a 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -534,6 +534,13 @@ enum {
 
        TRACE_GRAPH_DEPTH_START_BIT,
        TRACE_GRAPH_DEPTH_END_BIT,
+
+       /*
+        * To implement set_graph_notrace, if this bit is set, we ignore
+        * function graph tracing of called functions, until the return
+        * function is called to clear it.
+        */
+       TRACE_GRAPH_NOTRACE_BIT,
 };
 
 #define trace_recursion_set(bit)       do { (current)->trace_recursion |= (1<<(bit)); } while (0)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index b846d82..ecf543d 100644 (file)
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -188,6 +188,18 @@ int trace_graph_entry(struct ftrace_graph_ent *trace)
        int cpu;
        int pc;
 
+       if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT))
+               return 0;
+
+       if (ftrace_graph_notrace_addr(trace->func)) {
+               trace_recursion_set(TRACE_GRAPH_NOTRACE_BIT);
+               /*
+                * Need to return 1 to have the return called
+                * that will clear the NOTRACE bit.
+                */
+               return 1;
+       }
+
        if (!ftrace_trace_task(tr))
                return 0;
 
@@ -290,6 +302,11 @@ void trace_graph_return(struct ftrace_graph_ret *trace)
 
        ftrace_graph_addr_finish(trace);
 
+       if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
+               trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
+               return;
+       }
+
        local_irq_save(flags);
        cpu = raw_smp_processor_id();
        data = per_cpu_ptr(tr->trace_buffer.data, cpu);
@@ -315,6 +332,11 @@ static void trace_graph_thresh_return(struct ftrace_graph_ret *trace)
 {
        ftrace_graph_addr_finish(trace);
 
+       if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
+               trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
+               return;
+       }
+
        if (tracing_thresh &&
            (trace->rettime - trace->calltime < tracing_thresh))
                return;