linux-kernel - Re: [PATCH] printk: do not flush the logbuf into console driver in interrupt

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Date:	Thu, 17 May 2012 11:31:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Yanmin
	 "Zhang <yanmin_zhang@...ux.intel.com> (yanmin_zhang@...ux.intel.com)" 
	<yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH] printk: do not flush the logbuf into console driver in
 interrupt

On Thu, 2012-05-17 at 07:46 +0000, Liu, Chuansheng wrote:
> From: liu chuansheng <chuansheng.liu@...el.com>
> Subject: [PATCH] printk: do not flush the logbuf into console driver in interrupt
> 
> When irq handle tried to call printk, and it also has the chance to obtain the console sem,
> then flush the log buf to console driver,but the console driver often give several ms latency
> or more when much data in log buf existed, it will delay the irq handle.
> 
> The solution is when calling the printk in interrupt, just write the chars into log buf,
> and expect other threads to flush it into console driver.
> 
> Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
> 
> diff --git a/kernel/printk.c b/kernel/printk.c index b663c2c..99959e1 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -804,7 +804,8 @@ static int console_trylock_for_printk(unsigned int cpu)
>                  * the buffer. We need to hold the console semaphore
>                  * in order to do this test safely.
>                  */
> -               if (!can_use_console(cpu)) {
> +               if (!can_use_console(cpu) ||
> +                       (in_interrupt() && (!oops_in_progress))) {
>                         console_locked = 0;
>                         wake = 1;
>                         retval = 0;

Uhm no.. I would very much like to get my OOPSes from interrupt context
to make it out to the console.
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