Re: [PATCH] sched/debug: remove obsolete init_schedstats()

From: Kees Cook <keescook@chromium.org>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Guenter Roeck <groeck@google.com>
Subject: Re: [PATCH] sched/debug: remove obsolete init_schedstats()
Date: Wed, 2 Jun 2021 10:46:12 -0700	[thread overview]
Message-ID: <202106021045.7C51D37@keescook> (raw)
In-Reply-To: <20210602112108.1709635-1-eric.dumazet@gmail.com>

On Wed, Jun 02, 2021 at 04:21:08AM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> Revert "sched/debug: Fix 'schedstats=enable' cmdline option"
> 
> This reverts commit 4698f88c06b893f2acc0b443004a53bf490fde7c.
> 
> After commit 6041186a3258 ("init: initialize jump labels before command
> line option parsing") we can rely on jump label infra being ready for use
> when setup_schedstats() is called.

Ah yeah, good catch.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Guenter Roeck <groeck@google.com>
> Cc: Kees Cook <keescook@chromium.org>
> ---
>  kernel/sched/core.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 5226cc26a095f427dafa864ff37d39d529e2ba85..105fa6c73e7d9ded05683ee43a11e3b4461932d5 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3648,7 +3648,6 @@ int sysctl_numa_balancing(struct ctl_table *table, int write,
>  #ifdef CONFIG_SCHEDSTATS
>  
>  DEFINE_STATIC_KEY_FALSE(sched_schedstats);
> -static bool __initdata __sched_schedstats = false;
>  
>  static void set_schedstats(bool enabled)
>  {
> @@ -3672,16 +3671,11 @@ static int __init setup_schedstats(char *str)
>  	if (!str)
>  		goto out;
>  
> -	/*
> -	 * This code is called before jump labels have been set up, so we can't
> -	 * change the static branch directly just yet.  Instead set a temporary
> -	 * variable so init_schedstats() can do it later.
> -	 */
>  	if (!strcmp(str, "enable")) {
> -		__sched_schedstats = true;
> +		set_schedstats(true);
>  		ret = 1;
>  	} else if (!strcmp(str, "disable")) {
> -		__sched_schedstats = false;
> +		set_schedstats(false);
>  		ret = 1;
>  	}
>  out:
> @@ -3692,11 +3686,6 @@ static int __init setup_schedstats(char *str)
>  }
>  __setup("schedstats=", setup_schedstats);
>  
> -static void __init init_schedstats(void)
> -{
> -	set_schedstats(__sched_schedstats);
> -}
> -
>  #ifdef CONFIG_PROC_SYSCTL
>  int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
>  		size_t *lenp, loff_t *ppos)
> @@ -3718,8 +3707,6 @@ int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
>  	return err;
>  }
>  #endif /* CONFIG_PROC_SYSCTL */
> -#else  /* !CONFIG_SCHEDSTATS */
> -static inline void init_schedstats(void) {}
>  #endif /* CONFIG_SCHEDSTATS */
>  
>  /*
> @@ -8258,8 +8245,6 @@ void __init sched_init(void)
>  #endif
>  	init_sched_fair_class();
>  
> -	init_schedstats();
> -
>  	psi_init();
>  
>  	init_uclamp();
> -- 
> 2.32.0.rc0.204.g9fa02ecfa5-goog
> 

-- 
Kees Cook