linux-kernel - Re: [RFC][PATCH v6 1/2] printk: Make printk() completely async

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Message-ID: <20160322140427.GS22171@pathway.suse.cz>
Date:	Tue, 22 Mar 2016 15:04:27 +0100
From:	Petr Mladek <pmladek@...e.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.com>, Tejun Heo <tj@...nel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-kernel@...r.kernel.org,
	Byungchul Park <byungchul.park@....com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Jan Kara <jack@...e.cz>
Subject: Re: [RFC][PATCH v6 1/2] printk: Make printk() completely async

On Tue 2016-03-22 14:11:06, Petr Mladek wrote:
> On Tue 2016-03-22 02:25:29, Sergey Senozhatsky wrote:
> > +static void wake_up_klogd_work_func(struct irq_work *irq_work)
> > +{
> > +	int pending = __this_cpu_xchg(printk_pending, 0);
> > +
> > +	if (pending & PRINTK_PENDING_OUTPUT) {
> > +		/* If trylock fails, someone else is doing the printing */
> > +		if (console_trylock())
> > +			console_unlock();
> 
> This is called from IRQ context and thus keeps the original problem
> for printk_deferred(). We should try to
> wake_up_process(printk_kthread) when allowed.
> 
> 	if (pending & PRINTK_PENDING_OUTPUT) {
> 		if (printk_sync || !printk_kthread) {
> 			/* If trylock fails, someone else is printing. */
> 			if (console_trylock())
> 				console_unlock();
> 		} else {
> 			wake_up_process(printk_kthread);
> 		}
> 	}

Ah, this is in the 2nd patch. I am sorry for the noise.

Best Regards,
Petr