netdev - Re: [PATCH v3 4/6] net/core: apply pm_runtime_set_memalloc

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Message-ID: <Pine.LNX.4.44L0.1210291142000.22882-100000@netrider.rowland.org>
Date:	Mon, 29 Oct 2012 11:44:03 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ming Lei <ming.lei@...onical.com>
cc:	linux-kernel@...r.kernel.org, Oliver Neukum <oneukum@...e.de>,
	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>,
	Eric Dumazet <eric.dumazet@...il.com>,
	David Decotigny <david.decotigny@...gle.com>,
	Tom Herbert <therbert@...gle.com>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH v3 4/6] net/core: apply pm_runtime_set_memalloc_noio on
 network devices

On Mon, 29 Oct 2012, Ming Lei wrote:

> Deadlock might be caused by allocating memory with GFP_KERNEL in
> runtime_resume callback of network devices in iSCSI situation, so
> mark network devices and its ancestor as 'memalloc_noio_resume'
> with the introduced pm_runtime_set_memalloc_noio().

> @@ -1411,6 +1414,8 @@ int netdev_register_kobject(struct net_device *net)
>  	*groups++ = &netstat_group;
>  #endif /* CONFIG_SYSFS */
>  
> +	pm_runtime_set_memalloc_noio(dev, true);
> +
>  	error = device_add(dev);
>  	if (error)
>  		return error;

This is an example of what I described earlier.  The 
pm_runtime_set_memalloc_noio() call should come after device_add(), not 
before.

(Not to mention that this version of the code doesn't correctly handle
the case where device_add() fails.)

Alan Stern

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