linux-kernel - Re: [PATCH] usb: gadget: udc: lpc32xx: allocate descriptor with GFP

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Message-ID: <82974f50ad02342abd59b800a802f7adecabc0b9.camel@perches.com>
Date:   Fri, 10 May 2019 08:59:51 -0700
From:   Joe Perches <joe@...ches.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Felipe Balbi <balbi@...nel.org>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Sylvain Lemieux <slemieux.tyco@...il.com>,
        James Grant <james.grant@....com>, linux-usb@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: udc: lpc32xx: allocate descriptor with
 GFP_ATOMIC

On Fri, 2019-05-10 at 14:42 +0200, Alexandre Belloni wrote:
> Gadget drivers may queue request in interrupt context. This would lead to
> a descriptor allocation in that context. In that case we would hit
> BUG_ON(in_interrupt()) in __get_vm_area_node.
[]
> diff --git a/drivers/usb/gadget/udc/lpc32xx_udc.c b/drivers/usb/gadget/udc/lpc32xx_udc.c
[]
> @@ -938,7 +938,7 @@ static struct lpc32xx_usbd_dd_gad *udc_dd_alloc(struct lpc32xx_udc *udc)
>  	struct lpc32xx_usbd_dd_gad	*dd;
>  
>  	dd = (struct lpc32xx_usbd_dd_gad *) dma_pool_alloc(
> -			udc->dd_cache, (GFP_KERNEL | GFP_DMA), &dma);
> +			udc->dd_cache, (GFP_ATOMIC | GFP_DMA), &dma);

trivia:

This could fit nicely on a single line without the
unnecessary cast and the unnecessary parentheses
around the GFP_ types.