linux-kernel - Re: use of preempt_count instead of in

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Message-Id: <200803212120.59067.mb@bu3sch.de>
Date:	Fri, 21 Mar 2008 21:20:58 +0100
From:	Michael Buesch <mb@...sch.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Greg KH <greg@...ah.com>, heiko.carstens@...ibm.com,
	stern@...land.harvard.edu, hmh@....eng.br, david-b@...bell.net,
	rpurdie@...ys.net, linux-kernel@...r.kernel.org, mingo@...e.hu,
	geert@...ux-m68k.org, netdev@...r.kernel.org,
	schwidefsky@...ibm.com, linux-usb@...r.kernel.org,
	linux-wireless@...r.kernel.org, video4linux-list@...hat.com,
	stefanr@...6.in-berlin.de, lm-sensors@...sensors.org
Subject: Re: use of preempt_count instead of in_atomic() at leds-gpio.c

On Friday 21 March 2008 21:16:48 Michael Buesch wrote:
> On Friday 21 March 2008 20:59:50 Andrew Morton wrote:
> > They could of course be switched to using
> > kmalloc(GFP_ATOMIC)+memcpy()+schedule_task().  That's rather slow, but this
> > is not a performance-sensitive area.  But more seriously, this could lead
> > to messages getting lost from a dying machine.
> 
> Well, IMO drivers that need to sleep to transmit some data (to whatever,
> the screen or something) are not useful for debugging a crashing kernel anyway.
> Or how high is the possibility that it'd survive the actual sleep in the
> memory allocation? I'd say almost zero.
> So that schedule_task() is not that bad.

and

transmit_data_func()
{
	if (!oops_in_progress) {
		schedule_transmission_for_later();
	} else {
		/* We crash anyway, so we don't care about
		 * possible deadlocks from memory alloc sleeps
		 * or whatever. */
		close_eyes_and_transmit_it_now();
	}
}


-- 
Greetings Michael.
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