2018-01-26 15:53:09

by Jia-Ju Bai

Subject: [PATCH] bluetooth: btmrvl_main: Replace GFP_ATOMIC with GFP_KERNEL in btmrvl_send_sync_cmd

After checking all possible call chains to btmrvl_send_sync_cmd(),
my tool finds that this function is never called in atomic context,
namely never in an interrupt handler or holding a spinlock.
And it calls wait_event_interruptible_timeout() after bt_skb_alloc(),
so it indicates that btmrvl_send_sync_cmd()
can call function which can sleep.
Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/bluetooth/btmrvl_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btmrvl_main.c b/drivers/bluetooth/btmrvl_main.c
index b280d46..f6c694a 100644
--- a/drivers/bluetooth/btmrvl_main.c
+++ b/drivers/bluetooth/btmrvl_main.c
@@ -183,7 +183,7 @@ static int btmrvl_send_sync_cmd(struct btmrvl_private *priv, u16 opcode,
return -EFAULT;
}

- skb = bt_skb_alloc(HCI_COMMAND_HDR_SIZE + len, GFP_ATOMIC);
+ skb = bt_skb_alloc(HCI_COMMAND_HDR_SIZE + len, GFP_KERNEL);
if (!skb) {
BT_ERR("No free skb");
return -ENOMEM;
--
1.7.9.5

2018-02-07 08:58:00

by Marcel Holtmann

Subject: Re: [PATCH] bluetooth: btmrvl_main: Replace GFP_ATOMIC with GFP_KERNEL in btmrvl_send_sync_cmd

Hi Jia-Ju,

> After checking all possible call chains to btmrvl_send_sync_cmd(),
> my tool finds that this function is never called in atomic context,
> namely never in an interrupt handler or holding a spinlock.
> And it calls wait_event_interruptible_timeout() after bt_skb_alloc(),
> so it indicates that btmrvl_send_sync_cmd()
> can call function which can sleep.
> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL.
>
> This is found by a static analysis tool named DCNS written by myself.
>
> Signed-off-by: Jia-Ju Bai <[email protected]>
> ---
> drivers/bluetooth/btmrvl_main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel