linux-kernel - Re: [PATCH 02/12] locking/rtmutex: Move max_lock

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Message-ID: <202505091156.8B42E42@keescook>
Date: Fri, 9 May 2025 11:56:38 -0700
From: Kees Cook <kees@...nel.org>
To: Joel Granados <joel.granados@...nel.org>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Daniel Gomez <da.gomez@...sung.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>, Waiman Long <longman@...hat.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
	Helge Deller <deller@....de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>, linux-modules@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	rcu@...r.kernel.org, linux-mm@...ck.org,
	linux-parisc@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH 02/12] locking/rtmutex: Move max_lock_depth into rtmutex.c

On Fri, May 09, 2025 at 02:54:06PM +0200, Joel Granados wrote:
> Move the max_lock_depth sysctl table element and variable into
> rtmutex.c. Make the variable static as it no longer needs to be
> exported. Removed the rtmutex.h include from sysctl.c.
> 
> This is part of a greater effort to move ctl tables into their
> respective subsystems which will reduce the merge conflicts in
> kernel/sysctl.c.
> 
> Signed-off-by: Joel Granados <joel.granados@...nel.org>

Yup, all looks good, including the variable relocation.

Reviewed-by: Kees Cook <kees@...nel.org>

> ---
>  include/linux/rtmutex.h      |  2 --
>  kernel/locking/rtmutex.c     | 23 +++++++++++++++++++++++
>  kernel/locking/rtmutex_api.c |  5 -----
>  kernel/sysctl.c              | 12 ------------
>  4 files changed, 23 insertions(+), 19 deletions(-)
> 
> diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
> index 7d049883a08ace049384d70b4c97e3f4fb0e46f8..dc9a51cda97cdb6ac8e12be5209071744101b703 100644
> --- a/include/linux/rtmutex.h
> +++ b/include/linux/rtmutex.h
> @@ -18,8 +18,6 @@
>  #include <linux/rbtree_types.h>
>  #include <linux/spinlock_types_raw.h>
>  
> -extern int max_lock_depth; /* for sysctl */
> -
>  struct rt_mutex_base {
>  	raw_spinlock_t		wait_lock;
>  	struct rb_root_cached   waiters;
> diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
> index c80902eacd797c669dedcf10966a8cff38524b50..705a0e0fd72ab8da051e4227a5b89cb3d1539524 100644
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -29,6 +29,29 @@
>  #include "rtmutex_common.h"
>  #include "lock_events.h"
>  
> +/*
> + * Max number of times we'll walk the boosting chain:
> + */
> +static int max_lock_depth = 1024;
> +
> +static const struct ctl_table rtmutex_sysctl_table[] = {
> +	{
> +		.procname	= "max_lock_depth",
> +		.data		= &max_lock_depth,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_dointvec,
> +	},
> +};
> +
> +static int __init init_rtmutex_sysctl(void)
> +{
> +	register_sysctl_init("kernel", rtmutex_sysctl_table);
> +	return 0;
> +}
> +
> +subsys_initcall(init_rtmutex_sysctl);
> +
>  #ifndef WW_RT
>  # define build_ww_mutex()	(false)
>  # define ww_container_of(rtm)	NULL
> diff --git a/kernel/locking/rtmutex_api.c b/kernel/locking/rtmutex_api.c
> index 191e4720e546627aed0d7ec715673b1b8753b130..2b5da8af206da6ee72df1234a4db94f5c4f6f882 100644
> --- a/kernel/locking/rtmutex_api.c
> +++ b/kernel/locking/rtmutex_api.c
> @@ -8,11 +8,6 @@
>  #define RT_MUTEX_BUILD_MUTEX
>  #include "rtmutex.c"
>  
> -/*
> - * Max number of times we'll walk the boosting chain:
> - */
> -int max_lock_depth = 1024;
> -
>  /*
>   * Debug aware fast / slowpath lock,trylock,unlock
>   *
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 473133d9651eac4ef44b8b63a44b77189818ac08..a22f35013da0d838ef421fc5d192f00d1e70fb0f 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -59,9 +59,6 @@
>  #include <asm/nmi.h>
>  #include <asm/io.h>
>  #endif
> -#ifdef CONFIG_RT_MUTEXES
> -#include <linux/rtmutex.h>
> -#endif
>  
>  /* shared constants to be used in various sysctls */
>  const int sysctl_vals[] = { 0, 1, 2, 3, 4, 100, 200, 1000, 3000, INT_MAX, 65535, -1 };
> @@ -1709,15 +1706,6 @@ static const struct ctl_table kern_table[] = {
>  		.proc_handler	= proc_dointvec,
>  	},
>  #endif
> -#ifdef CONFIG_RT_MUTEXES
> -	{
> -		.procname	= "max_lock_depth",
> -		.data		= &max_lock_depth,
> -		.maxlen		= sizeof(int),
> -		.mode		= 0644,
> -		.proc_handler	= proc_dointvec,
> -	},
> -#endif
>  #ifdef CONFIG_TREE_RCU
>  	{
>  		.procname	= "panic_on_rcu_stall",
> 
> -- 
> 2.47.2
> 
> 

-- 
Kees Cook