Re: [PATCH v2 4/5] tracing: Unify the logic for function tracing options
Hi Steven,
Hi Steven,
On 6.04.21 г. 1:15, Steven Rostedt wrote:
@@ -235,30 +248,31 @@ static struct tracer function_trace;
static int
func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
{
- switch (bit) {
- case TRACE_FUNC_OPT_STACK:
- /* do nothing if already set */
- if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
- break;
+ ftrace_func_t func;
+ u32 new_flags_val;
Nit, but the variable should just be "new_flags", which is consistent with
old_flags. In the kernel we don't need to the variable names to be so
verbose.
- /* We can change this flag when not running. */
- if (tr->current_trace != _trace)
- break;
+ /* Do nothing if already set. */
+ if (!!set == !!(func_flags.val & bit))
+ return 0;
- unregister_ftrace_function(tr->ops);
+ /* We can change this flag only when not running. */
+ if (tr->current_trace != _trace)
+ return 0;
- if (set) {
- tr->ops->func = function_stack_trace_call;
- register_ftrace_function(tr->ops);
- } else {
- tr->ops->func = function_trace_call;
- register_ftrace_function(tr->ops);
- }
+ new_flags_val = (func_flags.val & ~(1UL << (bit - 1)));
+ new_flags_val |= (set << (bit - 1));
bit is already the mask, no need to shift it, nor there's no reason for the
extra set of parenthesis. And the above can be done in one line.
new_flags = (func_flags.val & ~bit) | (set ? bit : 0);
OK, I totally misinterpreted the meaning of the "bit" argument of the
function. I did not realized it is a mask. I was thinking the argument
gives only the number of the bit that changes (like 5 for the 5-th bit
inside the mask).
Thanks!
Yordan
Re: [PATCH v2 4/5] tracing: Unify the logic for function tracing options
On Mon, 29 Mar 2021 16:05:32 +0300
"Yordan Karadzhov (VMware)" wrote:
> Currently the logic for dealing with the options for function tracing
> has two different implementations. One is used when we set the flags
> (in "static int func_set_flag()") and another used when we initialize
> the tracer (in "static int function_trace_init()"). Those two
> implementations are meant to do essentially the same thing and they
> are both not very convenient for adding new options. In this patch
> we add a helper function that provides a single implementation of
> the logic for dealing with the options and we make it such that new
> options can be easily added.
>
> Signed-off-by: Yordan Karadzhov (VMware)
> ---
> kernel/trace/trace_functions.c | 66 --
> 1 file changed, 40 insertions(+), 26 deletions(-)
>
> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> index f93723ca66bc..6c912eb0508a 100644
> --- a/kernel/trace/trace_functions.c
> +++ b/kernel/trace/trace_functions.c
> @@ -27,13 +27,17 @@ function_trace_call(unsigned long ip, unsigned long
> parent_ip,
> static void
> function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
> struct ftrace_ops *op, struct ftrace_regs *fregs);
> +static ftrace_func_t select_trace_function(u32 flags_val);
> static struct tracer_flags func_flags;
>
> /* Our option */
> enum {
> + TRACE_FUNC_NO_OPTS = 0x0, /* No flags set. */
> TRACE_FUNC_OPT_STACK= 0x1,
> };
>
> +#define TRACE_FUNC_OPT_MASK (TRACE_FUNC_OPT_STACK)
> +
> int ftrace_allocate_ftrace_ops(struct trace_array *tr)
> {
> struct ftrace_ops *ops;
> @@ -97,12 +101,9 @@ static int function_trace_init(struct trace_array *tr)
> if (!tr->ops)
> return -ENOMEM;
>
> - /* Currently only the global instance can do stack tracing */
> - if (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
> - func_flags.val & TRACE_FUNC_OPT_STACK)
> - func = function_stack_trace_call;
> - else
> - func = function_trace_call;
> + func = select_trace_function(func_flags.val);
> + if (!func)
> + return -EINVAL;
>
> ftrace_init_array_ops(tr, func);
>
> @@ -205,6 +206,18 @@ function_stack_trace_call(unsigned long ip, unsigned
> long parent_ip,
> local_irq_restore(flags);
> }
>
> +static ftrace_func_t select_trace_function(u32 flags_val)
> +{
> + switch (flags_val & TRACE_FUNC_OPT_MASK) {
> + case TRACE_FUNC_NO_OPTS:
> + return function_trace_call;
> + case TRACE_FUNC_OPT_STACK:
> + return function_stack_trace_call;
> + default:
> + return NULL;
> + }
> +}
Is there a reason why you defined this function here and not before its
first use? When defining functions, I tend to try to define them before
their first use to not need to declare the static prototype above.
The reasons for doing the static prototype and using a static function is
usually because of #ifdef around the first use, and keeping the function
from being hidden by the #ifdef, or the static function already exists, and
then gets used in a function before it, where it's just easier to add the
static declaration than moving the function.
> +
> static struct tracer_opt func_opts[] = {
> #ifdef CONFIG_STACKTRACE
> { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
> @@ -213,7 +226,7 @@ static struct tracer_opt func_opts[] = {
> };
>
> static struct tracer_flags func_flags = {
> - .val = 0, /* By default: all flags disabled */
> + .val = TRACE_FUNC_NO_OPTS, /* By default: all flags disabled */
> .opts = func_opts
> };
>
> @@ -235,30 +248,31 @@ static struct tracer function_trace;
> static int
> func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
> {
> - switch (bit) {
> - case TRACE_FUNC_OPT_STACK:
> - /* do nothing if already set */
> - if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
> - break;
> + ftrace_func_t func;
> + u32 new_flags_val;
Nit, but the variable should just be "new_flags", which is consistent with
old_flags. In the kernel we don't need to the variable names to be so
verbose.
>
> - /* We can change this flag when not running. */
> - if (tr->current_trace != _trace)
> - break;
> + /* Do nothing if already set. */
> + if (!!set == !!(func_flags.val & bit))
> + return 0;
>
> - unregister_ftrace_function(tr->ops);
> + /* We can change this flag only when not running. */
> + if (tr->current_trace != _trace)
> + return 0;
>
> - if (set) {
> - tr->ops->func = function_stack_trace_call;
> - register_ftrace_function(tr->ops);
> - } else {
> - tr->ops->func = function_trace_call;
> -
[PATCH v2 4/5] tracing: Unify the logic for function tracing options
Currently the logic for dealing with the options for function tracing
has two different implementations. One is used when we set the flags
(in "static int func_set_flag()") and another used when we initialize
the tracer (in "static int function_trace_init()"). Those two
implementations are meant to do essentially the same thing and they
are both not very convenient for adding new options. In this patch
we add a helper function that provides a single implementation of
the logic for dealing with the options and we make it such that new
options can be easily added.
Signed-off-by: Yordan Karadzhov (VMware)
---
kernel/trace/trace_functions.c | 66 --
1 file changed, 40 insertions(+), 26 deletions(-)
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index f93723ca66bc..6c912eb0508a 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -27,13 +27,17 @@ function_trace_call(unsigned long ip, unsigned long
parent_ip,
static void
function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs);
+static ftrace_func_t select_trace_function(u32 flags_val);
static struct tracer_flags func_flags;
/* Our option */
enum {
+ TRACE_FUNC_NO_OPTS = 0x0, /* No flags set. */
TRACE_FUNC_OPT_STACK= 0x1,
};
+#define TRACE_FUNC_OPT_MASK(TRACE_FUNC_OPT_STACK)
+
int ftrace_allocate_ftrace_ops(struct trace_array *tr)
{
struct ftrace_ops *ops;
@@ -97,12 +101,9 @@ static int function_trace_init(struct trace_array *tr)
if (!tr->ops)
return -ENOMEM;
- /* Currently only the global instance can do stack tracing */
- if (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
- func_flags.val & TRACE_FUNC_OPT_STACK)
- func = function_stack_trace_call;
- else
- func = function_trace_call;
+ func = select_trace_function(func_flags.val);
+ if (!func)
+ return -EINVAL;
ftrace_init_array_ops(tr, func);
@@ -205,6 +206,18 @@ function_stack_trace_call(unsigned long ip, unsigned long
parent_ip,
local_irq_restore(flags);
}
+static ftrace_func_t select_trace_function(u32 flags_val)
+{
+ switch (flags_val & TRACE_FUNC_OPT_MASK) {
+ case TRACE_FUNC_NO_OPTS:
+ return function_trace_call;
+ case TRACE_FUNC_OPT_STACK:
+ return function_stack_trace_call;
+ default:
+ return NULL;
+ }
+}
+
static struct tracer_opt func_opts[] = {
#ifdef CONFIG_STACKTRACE
{ TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
@@ -213,7 +226,7 @@ static struct tracer_opt func_opts[] = {
};
static struct tracer_flags func_flags = {
- .val = 0, /* By default: all flags disabled */
+ .val = TRACE_FUNC_NO_OPTS, /* By default: all flags disabled */
.opts = func_opts
};
@@ -235,30 +248,31 @@ static struct tracer function_trace;
static int
func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
{
- switch (bit) {
- case TRACE_FUNC_OPT_STACK:
- /* do nothing if already set */
- if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
- break;
+ ftrace_func_t func;
+ u32 new_flags_val;
- /* We can change this flag when not running. */
- if (tr->current_trace != _trace)
- break;
+ /* Do nothing if already set. */
+ if (!!set == !!(func_flags.val & bit))
+ return 0;
- unregister_ftrace_function(tr->ops);
+ /* We can change this flag only when not running. */
+ if (tr->current_trace != _trace)
+ return 0;
- if (set) {
- tr->ops->func = function_stack_trace_call;
- register_ftrace_function(tr->ops);
- } else {
- tr->ops->func = function_trace_call;
- register_ftrace_function(tr->ops);
- }
+ new_flags_val = (func_flags.val & ~(1UL << (bit - 1)));
+ new_flags_val |= (set << (bit - 1));
- break;
- default:
+ func = select_trace_function(new_flags_val);
+ if (!func)
return -EINVAL;
- }
+
+ /* Check if there's anything to change. */
+ if (tr->ops->func == func)
+ return 0;
+
+ unregister_ftrace_function(tr->ops);
+ tr->ops->func = func;
+ register_ftrace_function(tr->ops);
return 0;
}
--
2.25.1
