From d39cdd2036a63eef17a14efbd969405ca5612886 Mon Sep 17 00:00:00 2001 From: Chunyu Hu Date: Tue, 8 Mar 2016 21:37:01 +0800 Subject: tracing: Make tracer_flags use the right set_flag callback When I was updating the ftrace_stress test of ltp. I encountered a strange phenomemon, excute following steps: echo nop > /sys/kernel/debug/tracing/current_tracer echo 0 > /sys/kernel/debug/tracing/options/funcgraph-cpu bash: echo: write error: Invalid argument check dmesg: [ 1024.903855] nop_test_refuse flag set to 0: we refuse.Now cat trace_options to see the result The reason is that the trace option test will randomly setup trace option under tracing/options no matter what the current_tracer is. but the set_tracer_option is always using the set_flag callback from the current_tracer. This patch adds a pointer to tracer_flags and make it point to the tracer it belongs to. When the option is setup, the set_flag of the right tracer will be used no matter what the the current_tracer is. And the old dummy_tracer_flags is used for all the tracers which doesn't have a tracer_flags, having issue to use it to save the pointer of a tracer. So remove it and use dynamic dummy tracer_flags for tracers needing a dummy tracer_flags, as a result, there are no tracers sharing tracer_flags, so remove the check code. And save the current tracer to trace_option_dentry seems not good as it may waste mem space when mount the debug/trace fs more than one time. Link: http://lkml.kernel.org/r/1457444222-8654-1-git-send-email-chuhu@redhat.com Signed-off-by: Chunyu Hu [ Fixed up function tracer options to work with the change ] Signed-off-by: Steven Rostedt --- kernel/trace/trace_functions.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'kernel/trace/trace_functions.c') diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index fcd41a166405..5a095c2e4b69 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -219,6 +219,8 @@ static void tracing_stop_function_trace(struct trace_array *tr) unregister_ftrace_function(tr->ops); } +static struct tracer function_trace; + static int func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set) { @@ -228,6 +230,10 @@ func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set) if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK)) break; + /* We can change this flag when not running. */ + if (tr->current_trace != &function_trace) + break; + unregister_ftrace_function(tr->ops); if (set) { -- cgit v1.2.3