[PATCH] d44: the poll handler b44_poll must not enable IRQ unconditionally

[PATCH] d44: the poll handler b44_poll must not enable IRQ unconditionally

[DDD]

net/core/netpoll.c::netpoll_send_skb() calls the poll handler when
it is available. As netconsole can be used from almost any context,
IRQ must not be enabled blindly in the NAPI handler of the driver
which supports netpoll.

Call trace:
netpoll_send_skb()
{
local_irq_save(flags)
  -> netpoll_poll()
    -> poll_napi()
      -> poll_one_napi()
        -> napi->poll()
            -> b44_poll()
local_irq_restore(flags)
}

Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
---
 drivers/net/b44.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/net/b44.c b/drivers/net/b44.c
index 0189dcd..e046943 100644
--- a/drivers/net/b44.c
+++ b/drivers/net/b44.c
@@ -847,23 +847,22 @@ static int b44_poll(struct napi_struct *napi, int budget)
 {
 	struct b44 *bp = container_of(napi, struct b44, napi);
 	int work_done;
+	unsigned long flags;
 
-	spin_lock_irq(&bp->lock);
+	spin_lock_irqsave(&bp->lock, flags);
 
 	if (bp->istat & (ISTAT_TX | ISTAT_TO)) {
 		/* spin_lock(&bp->tx_lock); */
 		b44_tx(bp);
 		/* spin_unlock(&bp->tx_lock); */
 	}
-	spin_unlock_irq(&bp->lock);
+	spin_unlock_irqrestore(&bp->lock, flags);
 
 	work_done = 0;
 	if (bp->istat & ISTAT_RX)
 		work_done += b44_rx(bp, budget);
 
 	if (bp->istat & ISTAT_ERRORS) {
-		unsigned long flags;
-
 		spin_lock_irqsave(&bp->lock, flags);
 		b44_halt(bp);
 		b44_init_rings(bp);
-- 
1.6.0.4

Re: [PATCH] d44: the poll handler b44_poll must not enable IRQ unconditionally

[Matt Mackall]

On Thu, Sep 17, 2009 at 10:10:47AM +0800, DDD wrote:
> net/core/netpoll.c::netpoll_send_skb() calls the poll handler when
> it is available. As netconsole can be used from almost any context,
> IRQ must not be enabled blindly in the NAPI handler of the driver
> which supports netpoll.
> 
> Call trace:
> netpoll_send_skb()
> {
> local_irq_save(flags)
>   -> netpoll_poll()
>     -> poll_napi()
>       -> poll_one_napi()
>         -> napi->poll()
>             -> b44_poll()
> local_irq_restore(flags)
> }
> 
> Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>

Acked-by: Matt Mackall <mpm@selenic.com>

> ---
>  drivers/net/b44.c |    7 +++----
>  1 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/b44.c b/drivers/net/b44.c
> index 0189dcd..e046943 100644
> --- a/drivers/net/b44.c
> +++ b/drivers/net/b44.c
> @@ -847,23 +847,22 @@ static int b44_poll(struct napi_struct *napi, int budget)
>  {
>  	struct b44 *bp = container_of(napi, struct b44, napi);
>  	int work_done;
> +	unsigned long flags;
>  
> -	spin_lock_irq(&bp->lock);
> +	spin_lock_irqsave(&bp->lock, flags);
>  
>  	if (bp->istat & (ISTAT_TX | ISTAT_TO)) {
>  		/* spin_lock(&bp->tx_lock); */
>  		b44_tx(bp);
>  		/* spin_unlock(&bp->tx_lock); */
>  	}
> -	spin_unlock_irq(&bp->lock);
> +	spin_unlock_irqrestore(&bp->lock, flags);
>  
>  	work_done = 0;
>  	if (bp->istat & ISTAT_RX)
>  		work_done += b44_rx(bp, budget);
>  
>  	if (bp->istat & ISTAT_ERRORS) {
> -		unsigned long flags;
> -
>  		spin_lock_irqsave(&bp->lock, flags);
>  		b44_halt(bp);
>  		b44_init_rings(bp);
> -- 
> 1.6.0.4
> 

-- 
Mathematics is the supreme nostalgia of our time.