linux-kernel - Re: [PATCH 2/2] drivers/isdn/hardware/mISDN: Use GFP

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Message-ID: <20100601080535.GA19288@gw.linux-pingi.de>
Date:	Tue, 1 Jun 2010 10:05:35 +0200
From:	Karsten Keil <isdn@...ux-pingi.de>
To:	Julia Lawall <julia@...u.dk>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 2/2] drivers/isdn/hardware/mISDN: Use GFP_ATOMIC when a
 lock is held

Hello Julia,

thanks for that report, the issue is valid, but I think the fix in that case
should be to move the allocation to an other place, to avoid wasting of
GFP_ATOMIC allocation. I will come up with an other fix.

Karsten


On Sun, May 30, 2010 at 03:49:40PM +0200, Julia Lawall wrote:
> From: Julia Lawall <julia@...u.dk>
> 
> The function inittiger is only called from nj_init_card, where a lock is held.
> 
> The semantic patch that makes this change is as follows:
> (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> @gfp exists@
> identifier fn;
> position p;
> @@
> 
> fn(...) {
>  ... when != spin_unlock_irqrestore
>      when any
>  GFP_KERNEL@p
>  ... when any
> }
> 
> @locked@
> identifier gfp.fn;
> @@
> 
> spin_lock_irqsave(...)
> ...  when != spin_unlock_irqrestore
> fn(...)
> 
> @depends on locked@
> position gfp.p;
> @@
> 
> - GFP_KERNEL@p
> + GFP_ATOMIC
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@...u.dk>
> 
> ---
>  drivers/isdn/hardware/mISDN/netjet.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff -u -p a/drivers/isdn/hardware/mISDN/netjet.c b/drivers/isdn/hardware/mISDN/netjet.c
> --- a/drivers/isdn/hardware/mISDN/netjet.c
> +++ b/drivers/isdn/hardware/mISDN/netjet.c
> @@ -320,12 +320,12 @@ inittiger(struct tiger_hw *card)
>  		return -ENOMEM;
>  	}
>  	for (i = 0; i < 2; i++) {
> -		card->bc[i].hsbuf = kmalloc(NJ_DMA_TXSIZE, GFP_KERNEL);
> +		card->bc[i].hsbuf = kmalloc(NJ_DMA_TXSIZE, GFP_ATOMIC);
>  		if (!card->bc[i].hsbuf) {
>  			pr_info("%s: no B%d send buffer\n", card->name, i + 1);
>  			return -ENOMEM;
>  		}
> -		card->bc[i].hrbuf = kmalloc(NJ_DMA_RXSIZE, GFP_KERNEL);
> +		card->bc[i].hrbuf = kmalloc(NJ_DMA_RXSIZE, GFP_ATOMIC);
>  		if (!card->bc[i].hrbuf) {
>  			pr_info("%s: no B%d recv buffer\n", card->name, i + 1);
>  			return -ENOMEM;
> --
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