netdev - Re: [PATCH] tools/runqslower: use _

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Date:   Tue, 6 Jul 2021 11:26:03 -0700
From:   Yonghong Song <yhs@...com>
To:     SanjayKumar J <vjsanjay@...il.com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <andrii@...nel.org>, <kafai@...com>,
        <songliubraving@...com>, <john.fastabend@...il.com>,
        <kpsingh@...nel.org>
CC:     <netdev@...r.kernel.org>, <bpf@...r.kernel.org>
Subject: Re: [PATCH] tools/runqslower: use __state instead of state

On 7/6/21 10:44 AM, SanjayKumar J wrote:
> 	task->state is renamed to task->__state in task_struct

Could you add a reference to
   2f064a59a11f ("sched: Change task_struct::state")
which added this change?

I think this should go to bpf tree as the change is in linus tree now.
Could you annotate the tag as "[PATCH bpf]" ("[PATCH bpf v2]")?

Please align comments to the left without margins.

> 
> 	Signed-off-by: SanjayKumar J <vjsanjay@...il.com>

This Singed-off-by is not needed.

You can add my Ack in the next revision:
Acked-by: Yonghong Song <yhs@...com>

> 
> Signed-off-by: SanjayKumar J <vjsanjay@...il.com>
> ---
>   tools/bpf/runqslower/runqslower.bpf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/bpf/runqslower/runqslower.bpf.c b/tools/bpf/runqslower/runqslower.bpf.c
> index 645530ca7e98..ab9353f2fd46 100644
> --- a/tools/bpf/runqslower/runqslower.bpf.c
> +++ b/tools/bpf/runqslower/runqslower.bpf.c
> @@ -74,7 +74,7 @@ int handle__sched_switch(u64 *ctx)
>   	u32 pid;
>   
>   	/* ivcsw: treat like an enqueue event and store timestamp */
> -	if (prev->state == TASK_RUNNING)
> +	if (prev->__state == TASK_RUNNING)

Currently, runqslower.bpf.c uses vmlinux.h.
I am thinking to use bpf_core_field_exists(), but we need to
single out task_struct structure from vmlinux.h
with both state and __state fields, we could make it work
by *changes* like

#define task_struct task_struct_orig
#include "vmlinux.h"
#undef task_struct

struct task_struct {
    ... state;
    ... __state;
...
};

Considering tools/bpf/runqslower is tied with a particular
kernel source, and vmlinux.h mostly derived from that
kernel source, I feel the above change is not necessary.

>   		trace_enqueue(prev);
>   
>   	pid = next->pid;
>