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ftrace: add stack trace to function tracer

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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>
This commit is contained in:
Steven Rostedt
2009-01-15 19:12:40 -05:00
committed by Ingo Molnar
parent 6c1a99afbd
commit 5361499101
3 changed files with 108 additions and 9 deletions
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26
kernel/trace/trace.c
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@ -835,10 +835,10 @@ ftrace(struct trace_array *tr, struct trace_array_cpu *data,
trace_function(tr, data, ip, parent_ip, flags, pc);
}
static void ftrace_trace_stack(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long flags,
int skip, int pc)
static void __ftrace_trace_stack(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long flags,
int skip, int pc)
{
#ifdef CONFIG_STACKTRACE
struct ring_buffer_event *event;
@ -846,9 +846,6 @@ static void ftrace_trace_stack(struct trace_array *tr,
struct stack_trace trace;
unsigned long irq_flags;
if (!(trace_flags & TRACE_ITER_STACKTRACE))
return;
event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
&irq_flags);
if (!event)
@ -869,12 +866,23 @@ static void ftrace_trace_stack(struct trace_array *tr,
#endif
}
static void ftrace_trace_stack(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long flags,
int skip, int pc)
{
if (!(trace_flags & TRACE_ITER_STACKTRACE))
return;
__ftrace_trace_stack(tr, data, flags, skip, pc);
}
void __trace_stack(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long flags,
int skip)
int skip, int pc)
{
ftrace_trace_stack(tr, data, flags, skip, preempt_count());
__ftrace_trace_stack(tr, data, flags, skip, pc);
}
static void ftrace_trace_userstack(struct trace_array *tr,