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authorSteven Rostedt <srostedt@redhat.com>2009-01-15 19:12:40 -0500
committerIngo Molnar <mingo@elte.hu>2009-01-16 12:15:32 +0100
commit5361499101306cfb776c3cfa0f69d0479bc63868 (patch)
tree1acf51a942abe6582e08ed86b4bbb98f9c095c89 /kernel/trace/trace_functions.c
parent6c1a99afbda99cd8d8c69d756387041567a13d87 (diff)
downloadop-kernel-dev-5361499101306cfb776c3cfa0f69d0479bc63868.zip
op-kernel-dev-5361499101306cfb776c3cfa0f69d0479bc63868.tar.gz
ftrace: add stack trace to function tracer
Impact: new feature to stack trace any function Chris Mason asked about being able to pick and choose a function and get a stack trace from it. This feature enables his request. # echo io_schedule > /debug/tracing/set_ftrace_filter # echo function > /debug/tracing/current_tracer # echo func_stack_trace > /debug/tracing/trace_options Produces the following in /debug/tracing/trace: kjournald-702 [001] 135.673060: io_schedule <-sync_buffer kjournald-702 [002] 135.673671: <= sync_buffer <= __wait_on_bit <= out_of_line_wait_on_bit <= __wait_on_buffer <= sync_dirty_buffer <= journal_commit_transaction <= kjournald Note, be careful about turning this on without filtering the functions. You may find that you have a 10 second lag between typing and seeing what you typed. This is why the stack trace for the function tracer does not use the same stack_trace flag as the other tracers use. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace/trace_functions.c')
-rw-r--r--kernel/trace/trace_functions.c84
1 files changed, 84 insertions, 0 deletions
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 9236d7e..3a5fa08 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -16,6 +16,8 @@
#include "trace.h"
+static struct trace_array *func_trace;
+
static void start_function_trace(struct trace_array *tr)
{
tr->cpu = get_cpu();
@@ -34,6 +36,7 @@ static void stop_function_trace(struct trace_array *tr)
static int function_trace_init(struct trace_array *tr)
{
+ func_trace = tr;
start_function_trace(tr);
return 0;
}
@@ -48,12 +51,93 @@ static void function_trace_start(struct trace_array *tr)
tracing_reset_online_cpus(tr);
}
+static void
+function_stack_trace_call(unsigned long ip, unsigned long parent_ip)
+{
+ struct trace_array *tr = func_trace;
+ struct trace_array_cpu *data;
+ unsigned long flags;
+ long disabled;
+ int cpu;
+ int pc;
+
+ if (unlikely(!ftrace_function_enabled))
+ return;
+
+ /*
+ * Need to use raw, since this must be called before the
+ * recursive protection is performed.
+ */
+ local_irq_save(flags);
+ cpu = raw_smp_processor_id();
+ data = tr->data[cpu];
+ disabled = atomic_inc_return(&data->disabled);
+
+ if (likely(disabled == 1)) {
+ pc = preempt_count();
+ /*
+ * skip over 5 funcs:
+ * __ftrace_trace_stack,
+ * __trace_stack,
+ * function_stack_trace_call
+ * ftrace_list_func
+ * ftrace_call
+ */
+ __trace_stack(tr, data, flags, 5, pc);
+ }
+
+ atomic_dec(&data->disabled);
+ local_irq_restore(flags);
+}
+
+static struct ftrace_ops trace_stack_ops __read_mostly =
+{
+ .func = function_stack_trace_call,
+};
+
+/* Our two options */
+enum {
+ TRACE_FUNC_OPT_STACK = 0x1,
+};
+
+static struct tracer_opt func_opts[] = {
+#ifdef CONFIG_STACKTRACE
+ { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
+#endif
+ { } /* Always set a last empty entry */
+};
+
+static struct tracer_flags func_flags = {
+ .val = 0, /* By default: all flags disabled */
+ .opts = func_opts
+};
+
+static int func_set_flag(u32 old_flags, u32 bit, int set)
+{
+ if (bit == TRACE_FUNC_OPT_STACK) {
+ /* do nothing if already set */
+ if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
+ return 0;
+
+ if (set)
+ register_ftrace_function(&trace_stack_ops);
+ else
+ unregister_ftrace_function(&trace_stack_ops);
+
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
static struct tracer function_trace __read_mostly =
{
.name = "function",
.init = function_trace_init,
.reset = function_trace_reset,
.start = function_trace_start,
+ .flags = &func_flags,
+ .set_flag = func_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_function,
#endif
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