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pstore/ftrace: Convert to its own enable/disable debugfs knob

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With this patch we no longer reuse function tracer infrastructure, now
we register our own tracer back-end via a debugfs knob.

It's a bit more code, but that is the only downside. On the bright side we
have:

- Ability to make persistent_ram module removable (when needed, we can
  move ftrace_ops struct into a module). Note that persistent_ram is still
  not removable for other reasons, but with this patch it's just one
  thing less to worry about;

- Pstore part is more isolated from the generic function tracer. We tried
  it already by registering our own tracer in available_tracers, but that
  way we're loosing ability to see the traces while we record them to
  pstore. This solution is somewhere in the middle: we only register
  "internal ftracer" back-end, but not the "front-end";

- When there is only pstore tracing enabled, the kernel will only write
  to the pstore buffer, omitting function tracer buffer (which, of course,
  still can be enabled via 'echo function > current_tracer').

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
This commit is contained in:
Anton Vorontsov 2012-07-17 14:26:15 -07:00
parent b4a871bce6
commit 65f8c95e46
7 changed files with 105 additions and 26 deletions
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15
kernel/trace/trace_functions.c
View file

@ -13,7 +13,6 @@
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/pstore.h>
#include <linux/fs.h>
#include "trace.h"
@ -75,10 +74,9 @@ function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip)
preempt_enable_notrace();
}
/* Our two options */
/* Our option */
enum {
TRACE_FUNC_OPT_STACK = 0x1,
TRACE_FUNC_OPT_PSTORE = 0x2,
};
static struct tracer_flags func_flags;
@ -106,12 +104,6 @@ function_trace_call(unsigned long ip, unsigned long parent_ip)
disabled = atomic_inc_return(&data->disabled);
if (likely(disabled == 1)) {
/*
* So far tracing doesn't support multiple buffers, so
* we make an explicit call for now.
*/
if (unlikely(func_flags.val & TRACE_FUNC_OPT_PSTORE))
pstore_ftrace_call(ip, parent_ip);
pc = preempt_count();
trace_function(tr, ip, parent_ip, flags, pc);
}
@ -176,9 +168,6 @@ static struct ftrace_ops trace_stack_ops __read_mostly =
static struct tracer_opt func_opts[] = {
#ifdef CONFIG_STACKTRACE
{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
#endif
#ifdef CONFIG_PSTORE_FTRACE
{ TRACER_OPT(func_pstore, TRACE_FUNC_OPT_PSTORE) },
#endif
{ } /* Always set a last empty entry */
};
@ -231,8 +220,6 @@ static int func_set_flag(u32 old_flags, u32 bit, int set)
register_ftrace_function(&trace_ops);
}
break;
case TRACE_FUNC_OPT_PSTORE:
break;
default:
return -EINVAL;