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Commit d39cdd20 authored by Chunyu Hu's avatar Chunyu Hu Committed by Steven Rostedt
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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: default avatarChunyu Hu <chuhu@redhat.com>
[ Fixed up function tracer options to work with the change ]
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f6cede5b

kernel/trace/trace.c

+14 −14
Original line number Diff line number Diff line
@@ -74,11 +74,6 @@ static struct tracer_opt dummy_tracer_opt[] = { 
	{ }

};



static struct tracer_flags dummy_tracer_flags = {

	.val = 0,

	.opts = dummy_tracer_opt

};



static int

dummy_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)

{
@@ -1258,12 +1253,20 @@ int __init register_tracer(struct tracer *type) 


	if (!type->set_flag)

		type->set_flag = &dummy_set_flag;

	if (!type->flags) {

		/*allocate a dummy tracer_flags*/

		type->flags = kmalloc(sizeof(*type->flags), GFP_KERNEL);

		if (!type->flags)

		type->flags = &dummy_tracer_flags;

	else

			return -ENOMEM;

		type->flags->val = 0;

		type->flags->opts = dummy_tracer_opt;

	} else

		if (!type->flags->opts)

			type->flags->opts = dummy_tracer_opt;



	/* store the tracer for __set_tracer_option */

	type->flags->trace = type;



	ret = run_tracer_selftest(type);

	if (ret < 0)

		goto out;
@@ -3505,7 +3508,7 @@ static int __set_tracer_option(struct trace_array *tr, 
			       struct tracer_flags *tracer_flags,

			       struct tracer_opt *opts, int neg)

{

	struct tracer *trace = tr->current_trace;

	struct tracer *trace = tracer_flags->trace;

	int ret;



	ret = trace->set_flag(tr, tracer_flags->val, opts->bit, !neg);
@@ -6391,11 +6394,8 @@ create_trace_option_files(struct trace_array *tr, struct tracer *tracer) 
		return;



	for (i = 0; i < tr->nr_topts; i++) {

		/*

		 * Check if these flags have already been added.

		 * Some tracers share flags.

		 */

		if (tr->topts[i].tracer->flags == tracer->flags)

		/* Make sure there's no duplicate flags. */

		if (WARN_ON_ONCE(tr->topts[i].tracer->flags == tracer->flags))

			return;

	}

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -345,6 +345,7 @@ struct tracer_opt { 
struct tracer_flags {

	u32			val;

	struct tracer_opt	*opts;

	struct tracer		*trace;

};



/* Makes more easy to define a tracer opt */

kernel/trace/trace_functions.c

+6 −0
Original line number Diff line number Diff line
@@ -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) {