linux-kernel - Re: [PATCH 1/3] picolcd: driver for PicoLCD HID device

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Date:	Thu, 25 Feb 2010 05:11:52 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	"Rick L. Vinyard, Jr." <rvinyard@...nmsu.edu>
Cc:	Bruno PrÃ©mont <bonbons@...ux-vserver.org>,
	"Jiri Kosina" <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, "Nicu Pavel" <npavel@...ner.com>
Subject: Re: [PATCH 1/3] picolcd: driver for PicoLCD HID device

Am Mittwoch, 24. Februar 2010 22:44:53 schrieb Rick L. Vinyard, Jr.:
> The issue, as I understand it is that non-interrupt code may obtain the
> lock and then the interrupt code is executed... hence the deadlock and the
> need to use spin_lock_irqsave() and spin_unlock_irqrestore().

Yes.

> If that is correct, is there any problem with the following approach?

Why not always a workqueue or alternatively spin_lock_irq() when
you are not in interrupt? This approach seems needlessly complicated.

Secondly, when you hold a spinlock, you must use GFP_ATOMIC.
GFP_NOIO is insufficient.

	Regards
		Oliver
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