linux-kernel - Re: [PATCH] net: dccp: Replace GFP_ATOMIC with GFP_KERNEL in dccp

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Message-ID: <8216dee8-5e52-421e-026a-4c75d654be54@gmail.com>
Date:   Mon, 9 Apr 2018 07:42:20 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>, gerrit@....abdn.ac.uk,
        davem@...emloft.net
Cc:     dccp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: dccp: Replace GFP_ATOMIC with GFP_KERNEL in
 dccp_init



On 04/09/2018 07:10 AM, Jia-Ju Bai wrote:
> dccp_init() is never called in atomic context.
> This function is only set as a parameter of module_init().
> 
> Despite never getting called from atomic context,
> dccp_init() calls __get_free_pages() with GFP_ATOMIC,
> which waits busily for allocation.

What do you mean by "waits busily" ?

GFP_ATOMIC does not sleep, does not wait.

> GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
> to avoid busy waiting 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>
> ---