LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Michael Büsch" <m@bues.ch>
To: Jia-Ju Bai <baijiaju1990@gmail.com>
Cc: Larry.Finger@lwfinger.net, kvalo@codeaurora.org,
	netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
	b43-dev@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: wireless: b43legacy: Replace GFP_ATOMIC with GFP_KERNEL in dma_tx_fragment
Date: Tue, 10 Apr 2018 18:57:56 +0200	[thread overview]
Message-ID: <20180410185756.35d4f601@wiggum> (raw)
In-Reply-To: <1523368459-32128-1-git-send-email-baijiaju1990@gmail.com>

[-- Attachment #1: Type: text/plain, Size: 2015 bytes --]

On Tue, 10 Apr 2018 21:54:19 +0800
Jia-Ju Bai <baijiaju1990@gmail.com> wrote:

> dma_tx_fragment() is never called in atomic context.
> 
> dma_tx_fragment() is only called by b43legacy_dma_tx(), which is 
> only called by b43legacy_tx_work().
> b43legacy_tx_work() is only set a parameter of INIT_WORK() in 
> b43legacy_wireless_init().
> 
> Despite never getting called from atomic context,
> dma_tx_fragment() calls alloc_skb() 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@gmail.com>
> ---
>  drivers/net/wireless/broadcom/b43legacy/dma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/broadcom/b43legacy/dma.c b/drivers/net/wireless/broadcom/b43legacy/dma.c
> index cfa617d..2f0c64c 100644
> --- a/drivers/net/wireless/broadcom/b43legacy/dma.c
> +++ b/drivers/net/wireless/broadcom/b43legacy/dma.c
> @@ -1064,7 +1064,7 @@ static int dma_tx_fragment(struct b43legacy_dmaring *ring,
>  	meta->dmaaddr = map_descbuffer(ring, skb->data, skb->len, 1);
>  	/* create a bounce buffer in zone_dma on mapping failure. */
>  	if (b43legacy_dma_mapping_error(ring, meta->dmaaddr, skb->len, 1)) {
> -		bounce_skb = alloc_skb(skb->len, GFP_ATOMIC | GFP_DMA);
> +		bounce_skb = alloc_skb(skb->len, GFP_KERNEL | GFP_DMA);
>  		if (!bounce_skb) {
>  			ring->current_slot = old_top_slot;
>  			ring->used_slots = old_used_slots;


Ack.
I think the GFP_ATOMIC came from the days where we did DMA operations
under spinlock instead of mutex.

The same thing can be done in b43.

Also 
setup_rx_descbuffer(ring, desc, meta, GFP_ATOMIC)
could be GFP_KERNEL in dma_rx().
This function is called from IRQ thread context.

-- 
Michael

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

  reply	other threads:[~2018-04-10 16:59 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-10 13:54 Jia-Ju Bai
2018-04-10 16:57 ` Michael Büsch [this message]
2018-04-30 10:27 ` Kalle Valo

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180410185756.35d4f601@wiggum \
    --to=m@bues.ch \
    --cc=Larry.Finger@lwfinger.net \
    --cc=b43-dev@lists.infradead.org \
    --cc=baijiaju1990@gmail.com \
    --cc=kvalo@codeaurora.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-wireless@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --subject='Re: [PATCH] net: wireless: b43legacy: Replace GFP_ATOMIC with GFP_KERNEL in dma_tx_fragment' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).