[PATCH] net: wireless: b43legacy: Replace GFP_ATOMIC with GFP_KERNEL in dma_tx_fragment

[PATCH] net: wireless: b43legacy: Replace GFP_ATOMIC with GFP_KERNEL in dma_tx_fragment

[Jia-Ju Bai]

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;
-- 
1.9.1

Re: [PATCH] net: wireless: b43legacy: Replace GFP_ATOMIC with GFP_KERNEL in dma_tx_fragment

[Michael Büsch]

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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

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Re: net: wireless: b43legacy: Replace GFP_ATOMIC with GFP_KERNEL in dma_tx_fragment

[Kalle Valo]

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>

Patch applied to wireless-drivers-next.git, thanks.

6e1d8d1470b2 net: wireless: b43legacy: Replace GFP_ATOMIC with GFP_KERNEL in dma_tx_fragment

-- 
https://patchwork.kernel.org/patch/10333217/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches