linux-kernel - Re: [PATCH] net: usb: hso: Replace GFP_ATOMIC with GFP_KERNEL in hso_create

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Message-ID: <20180410145928.GC10795@localhost>
Date:   Tue, 10 Apr 2018 16:59:28 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     davem@...emloft.net, andreas@...nade.info, johan@...nel.org,
        johannes.berg@...el.com, stephen@...workplumber.org,
        Linyu.Yuan@...atel-sbell.com.cn, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: usb: hso: Replace GFP_ATOMIC with GFP_KERNEL in
 hso_create_device

On Tue, Apr 10, 2018 at 10:35:24PM +0800, Jia-Ju Bai wrote:
> hso_create_device() is never called in atomic context.
> 
> The call chains ending up at hso_create_device() are:
> [1] hso_create_device() <- hso_create_bulk_serial_device() <- hso_probe()
> [2] hso_create_device() <- hso_create_mux_serial_device() <- hso_probe()
> [3] hso_create_device() <- hso_create_net_device() <- hso_probe()
> hso_probe() is set as ".probe" in struct usb_driver, 
> so it is not called in atomic context.
> 
> Despite never getting called from atomic context,
> hso_create_device() calls kzalloc() with GFP_ATOMIC,
> which does not sleep for allocation.
> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
> which can sleep and improve the possibility of sucessful allocation.
> 
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>

Thanks for the patch. This looks good to me.

Reviewed-by: Johan Hovold <johan@...nel.org>

Johan