linux-kernel - Re: [PATCH] usb: gadget: function: Replace GFP_KERNEL with GFP

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Message-ID: <xa1tegpk4iib.fsf@mina86.com>
Date:	Fri, 20 Feb 2015 18:09:32 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Tapasweni Pathak <tapaswenipathak@...il.com>, balbi@...com,
	gregkh@...uxfoundation.org, r.baldyga@...sung.com,
	andrzej.p@...sung.com, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	tapaswenipathak@...il.com, julia.lawall@...6.fr
Subject: Re: [PATCH] usb: gadget: function: Replace GFP_KERNEL with GFP_ATOMIC

On Fri, Feb 20 2015, Tapasweni Pathak wrote:
> To avoid deadlock, do not call blocking functions with spinlocks held.
>
> Replace GFP_KERNEL with GFP_ATOMIC, as the latter will fail if the heap
> doesn't have enough free pages but will not sleep and hence deadlock can
> be avoided.
>
> Found by Coccinelle.
>
> Signed-off-by: Tapasweni Pathak <tapaswenipathak@...il.com>
> ---
> Is there any other way this can be fixed as it is better to avoid GFP_ATOMIC?

I think there is.  A patchset will follow this reply.

>  drivers/usb/gadget/function/f_fs.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index af98b09..8a25d30 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -823,7 +823,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
>  		}
>
>  		if (io_data->aio) {
> -			req = usb_ep_alloc_request(ep->ep, GFP_KERNEL);
> +			req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC);
>  			if (unlikely(!req))
>  				goto error_lock;
>

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@...gle.com>--<xmpp:mina86@...ber.org>--ooO--(_)--Ooo--
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