* [PATCH] tracing: Use kstrdup_const() for constant hist field type
@ 2026-05-26 9:51 Yu Peng
2026-05-27 1:10 ` Masami Hiramatsu
0 siblings, 1 reply; 5+ messages in thread
From: Yu Peng @ 2026-05-26 9:51 UTC (permalink / raw)
To: Steven Rostedt
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-trace-kernel,
linux-kernel, Yu Peng
The HIST_FIELD_FL_CONST path duplicates the literal "u64" type with
kstrdup(), then releases it through kfree_const().
Use kstrdup_const() instead, avoiding the allocation for a .rodata string
while keeping the matching free helper.
Signed-off-by: Yu Peng <pengyu@kylinos.cn>
---
kernel/trace/trace_events_hist.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index eb2c2bc8bc3d..6ffe9f4720a0 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1992,7 +1992,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
if (flags & HIST_FIELD_FL_CONST) {
hist_field->fn_num = HIST_FIELD_FN_CONST;
hist_field->size = sizeof(u64);
- hist_field->type = kstrdup("u64", GFP_KERNEL);
+ hist_field->type = kstrdup_const("u64", GFP_KERNEL);
if (!hist_field->type)
goto free;
goto out;
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] tracing: Use kstrdup_const() for constant hist field type
2026-05-26 9:51 [PATCH] tracing: Use kstrdup_const() for constant hist field type Yu Peng
@ 2026-05-27 1:10 ` Masami Hiramatsu
2026-05-27 1:50 ` Steven Rostedt
0 siblings, 1 reply; 5+ messages in thread
From: Masami Hiramatsu @ 2026-05-27 1:10 UTC (permalink / raw)
To: Yu Peng
Cc: Steven Rostedt, Masami Hiramatsu, Mathieu Desnoyers,
linux-trace-kernel, linux-kernel
On Tue, 26 May 2026 17:51:05 +0800
Yu Peng <pengyu@kylinos.cn> wrote:
> The HIST_FIELD_FL_CONST path duplicates the literal "u64" type with
> kstrdup(), then releases it through kfree_const().
>
> Use kstrdup_const() instead, avoiding the allocation for a .rodata string
> while keeping the matching free helper.
>
Since we are using kfree_const() to free hist_field->type,
we can just point it as same as HIST_FIELD_FL_HITCOUNT case.
Thanks,
> Signed-off-by: Yu Peng <pengyu@kylinos.cn>
> ---
> kernel/trace/trace_events_hist.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index eb2c2bc8bc3d..6ffe9f4720a0 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -1992,7 +1992,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
> if (flags & HIST_FIELD_FL_CONST) {
> hist_field->fn_num = HIST_FIELD_FN_CONST;
> hist_field->size = sizeof(u64);
> - hist_field->type = kstrdup("u64", GFP_KERNEL);
> + hist_field->type = kstrdup_const("u64", GFP_KERNEL);
> if (!hist_field->type)
> goto free;
> goto out;
> --
> 2.43.0
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] tracing: Use kstrdup_const() for constant hist field type
2026-05-27 1:10 ` Masami Hiramatsu
@ 2026-05-27 1:50 ` Steven Rostedt
2026-05-27 2:18 ` [PATCH v2] tracing: Point constant hist field type to string literal Yu Peng
0 siblings, 1 reply; 5+ messages in thread
From: Steven Rostedt @ 2026-05-27 1:50 UTC (permalink / raw)
To: Masami Hiramatsu (Google)
Cc: Yu Peng, Mathieu Desnoyers, linux-trace-kernel, linux-kernel
On Wed, 27 May 2026 10:10:15 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> On Tue, 26 May 2026 17:51:05 +0800
> Yu Peng <pengyu@kylinos.cn> wrote:
>
> > The HIST_FIELD_FL_CONST path duplicates the literal "u64" type with
> > kstrdup(), then releases it through kfree_const().
> >
> > Use kstrdup_const() instead, avoiding the allocation for a .rodata string
> > while keeping the matching free helper.
> >
>
> Since we are using kfree_const() to free hist_field->type,
> we can just point it as same as HIST_FIELD_FL_HITCOUNT case.
>
Agreed.
> Thanks,
>
> > Signed-off-by: Yu Peng <pengyu@kylinos.cn>
> > ---
> > kernel/trace/trace_events_hist.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > index eb2c2bc8bc3d..6ffe9f4720a0 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -1992,7 +1992,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
> > if (flags & HIST_FIELD_FL_CONST) {
> > hist_field->fn_num = HIST_FIELD_FN_CONST;
> > hist_field->size = sizeof(u64);
> > - hist_field->type = kstrdup("u64", GFP_KERNEL);
> > + hist_field->type = kstrdup_const("u64", GFP_KERNEL);
This can simply be made to point to "u64".
Thanks,
-- Steve
> > if (!hist_field->type)
> > goto free;
> > goto out;
> > --
> > 2.43.0
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2] tracing: Point constant hist field type to string literal
2026-05-27 1:50 ` Steven Rostedt
@ 2026-05-27 2:18 ` Yu Peng
2026-05-27 2:26 ` Steven Rostedt
0 siblings, 1 reply; 5+ messages in thread
From: Yu Peng @ 2026-05-27 2:18 UTC (permalink / raw)
To: rostedt
Cc: linux-kernel, linux-trace-kernel, mathieu.desnoyers, mhiramat,
pengyu
The HIST_FIELD_FL_CONST path uses the fixed "u64" type string.
Point hist_field->type directly to the string literal, matching the
HIST_FIELD_FL_HITCOUNT path. The release path already uses kfree_const(),
so no duplication is needed.
Signed-off-by: Yu Peng <pengyu@kylinos.cn>
---
Changes in v2:
- Point hist_field->type directly to "u64" as suggested.
kernel/trace/trace_events_hist.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index eb2c2bc8bc3d5..b50f2bd5ff771 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1992,9 +1992,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
if (flags & HIST_FIELD_FL_CONST) {
hist_field->fn_num = HIST_FIELD_FN_CONST;
hist_field->size = sizeof(u64);
- hist_field->type = kstrdup("u64", GFP_KERNEL);
- if (!hist_field->type)
- goto free;
+ hist_field->type = "u64";
goto out;
}
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] tracing: Point constant hist field type to string literal
2026-05-27 2:18 ` [PATCH v2] tracing: Point constant hist field type to string literal Yu Peng
@ 2026-05-27 2:26 ` Steven Rostedt
0 siblings, 0 replies; 5+ messages in thread
From: Steven Rostedt @ 2026-05-27 2:26 UTC (permalink / raw)
To: Yu Peng; +Cc: linux-kernel, linux-trace-kernel, mathieu.desnoyers, mhiramat
On Wed, 27 May 2026 10:18:27 +0800
Yu Peng <pengyu@kylinos.cn> wrote:
> The HIST_FIELD_FL_CONST path uses the fixed "u64" type string.
>
> Point hist_field->type directly to the string literal, matching the
> HIST_FIELD_FL_HITCOUNT path. The release path already uses kfree_const(),
> so no duplication is needed.
>
> Signed-off-by: Yu Peng <pengyu@kylinos.cn>
> ---
> Changes in v2:
> - Point hist_field->type directly to "u64" as suggested
All new versions of a patch need to start a new thread. Please resend
this as a new thread and not a reply.
-- Steve
>
> kernel/trace/trace_events_hist.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index eb2c2bc8bc3d5..b50f2bd5ff771 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -1992,9 +1992,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
> if (flags & HIST_FIELD_FL_CONST) {
> hist_field->fn_num = HIST_FIELD_FN_CONST;
> hist_field->size = sizeof(u64);
> - hist_field->type = kstrdup("u64", GFP_KERNEL);
> - if (!hist_field->type)
> - goto free;
> + hist_field->type = "u64";
> goto out;
> }
>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2026-05-27 2:26 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2026-05-26 9:51 [PATCH] tracing: Use kstrdup_const() for constant hist field type Yu Peng
2026-05-27 1:10 ` Masami Hiramatsu
2026-05-27 1:50 ` Steven Rostedt
2026-05-27 2:18 ` [PATCH v2] tracing: Point constant hist field type to string literal Yu Peng
2026-05-27 2:26 ` Steven Rostedt
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