linux-kernel - Re: [PATCH 1/4] printk: Re-add irqsave/restore in printk

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Message-ID: <20140504145847.GA7433@quack.suse.cz>
Date:	Sun, 4 May 2014 16:58:47 +0200
From:	Jan Kara <jack@...e.cz>
To:	John Stultz <john.stultz@...aro.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Bohac <jbohac@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 1/4] printk: Re-add irqsave/restore in printk_sched

On Fri 02-05-14 15:09:15, John Stultz wrote:
> A commit in akpm's tree (printk: remove separate printk_sched
> buffers...), removed the printk_sched irqsave/restore lines
> since it was safe for current users. Since we may be expanding
> usage of printk_sched(), re-add the irqsave/restore logic
> to make the functionality more generally safe.
  So I'm just wondering: Do you have anything particular for which you need
interrupts disabled? Won't e.g. disabling preemption be enough?

								Honza

> Cc: Jan Kara <jack@...e.cz>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Jiri Bohac <jbohac@...e.cz>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  kernel/printk/printk.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 82d19e6..bf62f2b 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2586,15 +2586,18 @@ void wake_up_klogd(void)
>  
>  int printk_sched(const char *fmt, ...)
>  {
> +	unsigned long flags;
>  	va_list args;
>  	int r;
>  
> +	local_irq_save(flags);
>  	va_start(args, fmt);
>  	r = vprintk_emit(0, SCHED_MESSAGE_LOGLEVEL, NULL, 0, fmt, args);
>  	va_end(args);
>  
>  	__this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
>  	irq_work_queue(&__get_cpu_var(wake_up_klogd_work));
> +	local_irq_restore(flags);
>  
>  	return r;
>  }
> -- 
> 1.9.1
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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