linux-kernel - Re: [PATCH v3 2/6] PM / Runtime: introduce pm_runtime_set[get]_memalloc

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Message-ID: <Pine.LNX.4.44L0.1210311117310.1954-100000@iolanthe.rowland.org>
Date:	Wed, 31 Oct 2012 11:20:02 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ming Lei <ming.lei@...onical.com>
cc:	Oliver Neukum <oneukum@...e.de>, <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Jens Axboe <axboe@...nel.dk>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	<netdev@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-pm@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH v3 2/6] PM / Runtime: introduce pm_runtime_set[get]_memalloc_noio()

On Wed, 31 Oct 2012, Ming Lei wrote:

> The below idea may help the problem which 'memalloc_noio' flag isn't set during
> usb_reset_device().
> 
> - for usb mass storage device, call pm_runtime_set_memalloc_noio(true)
>   inside usb_stor_probe2() and uas_probe(), and call
>   pm_runtime_set_memalloc_noio(false) inside uas_disconnect()
>   and usb_stor_disconnect().

Why would you want to do that?  The probe and disconnect routines
usually -- but not always -- run in the khubd thread.  Surely you don't
want to prevent khubd from using GFP_KERNEL?

And what if probe runs in khubd but disconnect runs in a different 
thread?

Alan Stern

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