Re: [PATCH 1/2] bug: Provide WARN_ON.*DEFERRED() macros for console deferred output

[K Prateek Nayak]

Hello Sebastian,

On 6/23/2026 7:56 PM, Sebastian Andrzej Siewior wrote:
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -196,7 +196,7 @@ void __warn_printf(const char *fmt, struct pt_regs *regs)
>  
>  static enum bug_trap_type __report_bug(struct bug_entry *bug, unsigned long bugaddr, struct pt_regs *regs)
>  {
> -	bool warning, once, done, no_cut, has_args;
> +	bool warning, once, done, no_cut, has_args, deferred;
>  	const char *file, *fmt;
>  	unsigned line;
>  
> @@ -219,6 +219,7 @@ static enum bug_trap_type __report_bug(struct bug_entry *bug, unsigned long buga
>  	done     = bug->flags & BUGFLAG_DONE;
>  	no_cut   = bug->flags & BUGFLAG_NO_CUT_HERE;
>  	has_args = bug->flags & BUGFLAG_ARGS;
> +	deferred = bug->flags & BUGFLAG_DEFERRED;
>  
>  	if (warning && once) {
>  		if (done)
> @@ -229,7 +230,10 @@ static enum bug_trap_type __report_bug(struct bug_entry *bug, unsigned long buga
>  		 */
>  		bug->flags |= BUGFLAG_DONE;
>  	}
> -
> +	if (deferred) {
> +		preempt_disable_notrace();
> +		printk_deferred_enter();
> +	}
>  	/*
>  	 * BUG() and WARN_ON() families don't print a custom debug message
>  	 * before triggering the exception handler, so we must add the
> @@ -245,6 +249,10 @@ static enum bug_trap_type __report_bug(struct bug_entry *bug, unsigned long buga
>  		/* this is a WARN_ON rather than BUG/BUG_ON */
>  		__warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs,
>  		       NULL);
> +		if (deferred) {
> +			printk_deferred_exit();
> +			preempt_enable_notrace();
> +		}
>  		return BUG_TRAP_TYPE_WARN;

nit.

Instead of replicating these bits, can we replace that return with a
"goto out" ...

>  	}
>  
> @@ -254,6 +262,10 @@ static enum bug_trap_type __report_bug(struct bug_entry *bug, unsigned long buga
>  		pr_crit("kernel BUG at %pB [verbose debug info unavailable]\n",
>  			(void *)bugaddr);
>  

out:

> +	if (deferred) {
> +		printk_deferred_exit();
> +		preempt_enable_notrace();
> +	}
>  	return BUG_TRAP_TYPE_BUG;

... and replace this return with a:

    return (warning) ? BUG_TRAP_TYPE_WARN : BUG_TRAP_TYPE_BUG;

Looks a tab bit cleaner to my eyes. Thoughts?

>  }
>  

-- 
Thanks and Regards,
Prateek