diff mbox series

[RFC,01/10] perf: Remove get_perf_callchain() 'init_nr' argument

Message ID b9e939c77fa74baec8d1b2d3001958f12ef16eb9.1699487758.git.jpoimboe@kernel.org
State New
Headers
Series perf: user space sframe unwinding |

Commit Message

Josh Poimboeuf Nov. 9, 2023, 12:41 a.m. UTC 
  The 'init_nr' argument has double duty: it's used to initialize both the
number of contexts and the number of stack entries.  That's confusing
and the callers always pass zero anyway.  Hard code the zero.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 include/linux/perf_event.h |  2 +-
 kernel/bpf/stackmap.c      |  4 ++--
 kernel/events/callchain.c  | 12 ++++++------
 kernel/events/core.c       |  2 +-
 4 files changed, 10 insertions(+), 10 deletions(-)

Comments

Namhyung Kim Nov. 11, 2023, 6:09 a.m. UTC | #1 
Hello,

On Wed, Nov 8, 2023 at 4:43 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> The 'init_nr' argument has double duty: it's used to initialize both the
> number of contexts and the number of stack entries.  That's confusing
> and the callers always pass zero anyway.  Hard code the zero.

IIRC it was used to skip a number of first stack entries in BPF.
I changed the code to not use init_nr but forgot to update
the perf code.

Acked-by: Namhyung Kim <Namhyung@kernel.org>

Thanks,
Namhyung

>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  include/linux/perf_event.h |  2 +-
>  kernel/bpf/stackmap.c      |  4 ++--
>  kernel/events/callchain.c  | 12 ++++++------
>  kernel/events/core.c       |  2 +-
>  4 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index afb028c54f33..f4b05954076c 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1533,7 +1533,7 @@ DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
>  extern void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
>  extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
>  extern struct perf_callchain_entry *
> -get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
> +get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
>                    u32 max_stack, bool crosstask, bool add_mark);
>  extern int get_callchain_buffers(int max_stack);
>  extern void put_callchain_buffers(void);
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index d6b277482085..b0b0fbff7c18 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -294,7 +294,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
>         if (max_depth > sysctl_perf_event_max_stack)
>                 max_depth = sysctl_perf_event_max_stack;
>
> -       trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
> +       trace = get_perf_callchain(regs, kernel, user, max_depth,
>                                    false, false);
>
>         if (unlikely(!trace))
> @@ -420,7 +420,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
>         else if (kernel && task)
>                 trace = get_callchain_entry_for_task(task, max_depth);
>         else
> -               trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
> +               trace = get_perf_callchain(regs, kernel, user, max_depth,
>                                            false, false);
>         if (unlikely(!trace))
>                 goto err_fault;
> diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
> index 1273be84392c..1e135195250c 100644
> --- a/kernel/events/callchain.c
> +++ b/kernel/events/callchain.c
> @@ -177,7 +177,7 @@ put_callchain_entry(int rctx)
>  }
>
>  struct perf_callchain_entry *
> -get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
> +get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
>                    u32 max_stack, bool crosstask, bool add_mark)
>  {
>         struct perf_callchain_entry *entry;
> @@ -188,11 +188,11 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
>         if (!entry)
>                 return NULL;
>
> -       ctx.entry     = entry;
> -       ctx.max_stack = max_stack;
> -       ctx.nr        = entry->nr = init_nr;
> -       ctx.contexts       = 0;
> -       ctx.contexts_maxed = false;
> +       ctx.entry               = entry;
> +       ctx.max_stack           = max_stack;
> +       ctx.nr                  = entry->nr = 0;
> +       ctx.contexts            = 0;
> +       ctx.contexts_maxed      = false;
>
>         if (kernel && !user_mode(regs)) {
>                 if (add_mark)
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 683dc086ef10..b0d62df7df4e 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7600,7 +7600,7 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
>         if (!kernel && !user)
>                 return &__empty_callchain;
>
> -       callchain = get_perf_callchain(regs, 0, kernel, user,
> +       callchain = get_perf_callchain(regs, kernel, user,
>                                        max_stack, crosstask, true);
>         return callchain ?: &__empty_callchain;
>  }
> --
> 2.41.0
>
diff mbox series

Patch

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index afb028c54f33..f4b05954076c 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1533,7 +1533,7 @@  DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
 extern void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
 extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs);
 extern struct perf_callchain_entry *
-get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
+get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
 		   u32 max_stack, bool crosstask, bool add_mark);
 extern int get_callchain_buffers(int max_stack);
 extern void put_callchain_buffers(void);
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index d6b277482085..b0b0fbff7c18 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -294,7 +294,7 @@  BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 	if (max_depth > sysctl_perf_event_max_stack)
 		max_depth = sysctl_perf_event_max_stack;
 
-	trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
+	trace = get_perf_callchain(regs, kernel, user, max_depth,
 				   false, false);
 
 	if (unlikely(!trace))
@@ -420,7 +420,7 @@  static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 	else if (kernel && task)
 		trace = get_callchain_entry_for_task(task, max_depth);
 	else
-		trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
+		trace = get_perf_callchain(regs, kernel, user, max_depth,
 					   false, false);
 	if (unlikely(!trace))
 		goto err_fault;
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 1273be84392c..1e135195250c 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -177,7 +177,7 @@  put_callchain_entry(int rctx)
 }
 
 struct perf_callchain_entry *
-get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
+get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
 		   u32 max_stack, bool crosstask, bool add_mark)
 {
 	struct perf_callchain_entry *entry;
@@ -188,11 +188,11 @@  get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
 	if (!entry)
 		return NULL;
 
-	ctx.entry     = entry;
-	ctx.max_stack = max_stack;
-	ctx.nr	      = entry->nr = init_nr;
-	ctx.contexts       = 0;
-	ctx.contexts_maxed = false;
+	ctx.entry		= entry;
+	ctx.max_stack		= max_stack;
+	ctx.nr			= entry->nr = 0;
+	ctx.contexts		= 0;
+	ctx.contexts_maxed	= false;
 
 	if (kernel && !user_mode(regs)) {
 		if (add_mark)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 683dc086ef10..b0d62df7df4e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7600,7 +7600,7 @@  perf_callchain(struct perf_event *event, struct pt_regs *regs)
 	if (!kernel && !user)
 		return &__empty_callchain;
 
-	callchain = get_perf_callchain(regs, 0, kernel, user,
+	callchain = get_perf_callchain(regs, kernel, user,
 				       max_stack, crosstask, true);
 	return callchain ?: &__empty_callchain;
 }