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Message-ID: <ZdXB-7E7kTyFGhDU@alley>
Date: Wed, 21 Feb 2024 10:55:38 +0100
From: Petr Mladek <pmladek@...e.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH printk v2 07/26] printk: Check
printk_deferred_enter()/_exit() usage
On Sun 2024-02-18 20:03:07, John Ogness wrote:
> From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
>
> Add validation that printk_deferred_enter()/_exit() are called in
> non-migration contexts.
>
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -159,13 +159,16 @@ __printf(1, 2) __cold int _printk_deferred(const char *fmt, ...);
>
> extern void __printk_safe_enter(void);
> extern void __printk_safe_exit(void);
It seems that these two does not longer need to stay in
the global linux/printk.h. The declaration can be
moved to kernel/printk/internal.h (with 'extern' removed).
> +extern void __printk_deferred_enter(void);
> +extern void __printk_deferred_exit(void);
> +
> /*
> * The printk_deferred_enter/exit macros are available only as a hack for
> * some code paths that need to defer all printk console printing. Interrupts
> * must be disabled for the deferred duration.
> */
> -#define printk_deferred_enter __printk_safe_enter
> -#define printk_deferred_exit __printk_safe_exit
> +#define printk_deferred_enter() __printk_deferred_enter()
> +#define printk_deferred_exit() __printk_deferred_exit()
>
> /*
> * Please don't use printk_ratelimit(), because it shares ratelimiting state
> diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
> index 6d10927a07d8..8d9408d653de 100644
> --- a/kernel/printk/printk_safe.c
> +++ b/kernel/printk/printk_safe.c
> @@ -26,6 +26,18 @@ void __printk_safe_exit(void)
> this_cpu_dec(printk_context);
> }
>
> +void __printk_deferred_enter(void)
> +{
> + cant_migrate();
> + this_cpu_inc(printk_context);
I would prefer to call __printk_safe_enter() here to make
it clear that they update printk_context the same way
and have the same effect.
Let's make compiler to do the inlining.
> +}
> +
> +void __printk_deferred_exit(void)
> +{
> + cant_migrate();
> + this_cpu_dec(printk_context);
ditto
> +}
> +
> asmlinkage int vprintk(const char *fmt, va_list args)
> {
> #ifdef CONFIG_KGDB_KDB
With the two changes:
Reviewed-by: Petr Mladek <pmladek@...e.com>
Best Regards,
Petr
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