linux-kernel - Re: [PATCH v3] printk: Have printk() never buffer its data

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Date:	Tue, 26 Jun 2012 09:30:55 -0700
From:	Joe Perches <joe@...ches.com>
To:	Kay Sievers <kay@...y.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Wu Fengguang <fengguang.wu@...el.com>,
	"Paul E. McKenney" <paulmck@...ibm.com>
Subject: Re: [PATCH v3] printk: Have printk() never buffer its data

On Tue, 2012-06-26 at 18:07 +0200, Kay Sievers wrote:
[]

Just a couple trivial notes:

> diff --git a/kernel/printk.c b/kernel/printk.c
[]
> @@ -1795,6 +1831,7 @@ static u32 console_idx;
>   */
>  void console_unlock(void)
>  {
> +	static char text[LOG_LINE_MAX];

Is this static to avoid excessive stack?
Might be useful to note that.

>  	static u64 seen_seq;
>  	unsigned long flags;
>  	bool wake_klogd = false;
> @@ -1807,10 +1844,37 @@ void console_unlock(void)
>  
>  	console_may_schedule = 0;
>  
> +	/* flush buffered message fragment immediately to console */
> +	raw_spin_lock_irqsave(&logbuf_lock, flags);
> +	if (cont_cons_len && (cont_cons < cont_cons_len || !cont_len)) {
> +		size_t textlen = 0;
> +		size_t len;
> +
> +		len = cont_cons_len - cont_cons;
> +		if (!cont_cons)
> +			textlen = print_time(cont_ts_nsec, text);
> +		memcpy(text + textlen, cont_buf + cont_cons, len);

This could overrun the 512 bytes of text yes?


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