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

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Message-ID: <Pine.LNX.4.44L0.1210311139300.1954-100000@iolanthe.rowland.org>
Date:	Wed, 31 Oct 2012 11:41:07 -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, Alan Stern wrote:

> 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?

Sorry, I misread your message.  You are setting the device's flag, not 
the thread's flag.

This still doesn't help in this case where CONFIG_PM_RUNTIME is 
disabled.  I think it will be simpler to set the noio flag during every 
device reset.

Alan Stern

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