netdev - Re: [PATCH] netpoll: Don't call driver methods from interrupt context.

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Message-Id: <20140304.160825.893718566461536483.davem@davemloft.net>
Date:	Tue, 04 Mar 2014 16:08:25 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	ebiederm@...ssion.com
Cc:	netdev@...r.kernel.org, xiyou.wangcong@...il.com, mpm@...enic.com,
	satyam.sharma@...il.com
Subject: Re: [PATCH] netpoll: Don't call driver methods from interrupt
 context.

From: ebiederm@...ssion.com (Eric W. Biederman)
Date: Mon, 03 Mar 2014 12:40:05 -0800

> <IRQ>  [<ffffffff8104934c>] warn_slowpath_common+0x85/0x9d
> [<ffffffff8104937e>] warn_slowpath_null+0x1a/0x1c
> [<ffffffff81429aa7>] skb_release_head_state+0x7b/0xe1
> [<ffffffff814297e1>] __kfree_skb+0x16/0x81
> [<ffffffff814298a0>] consume_skb+0x54/0x69
> [<ffffffffa015925b>] bnx2_tx_int.clone.6+0x1b0/0x33e [bnx2]

Other drivers, such as bnx2x, uses dev_kfree_skb_any(), probably
exactly to deal with this situation.

If in_irq() is true or interrupts are disabled, __dev_kfree_skb_any
will use __dev_kfree_skb_irq, which will queue up the SKB and schedule
a software interrupt to do the actual work.

For example, see this commit, which we probably just need to duplicate
into other poll supporting drivers:

commit 40955532bc9d865999dfc58b7896605d58650655
Author: Vladislav Zolotarov <vladz@...adcom.com>
Date:   Sun May 22 10:06:58 2011 +0000

    bnx2x: call dev_kfree_skb_any instead of dev_kfree_skb
    
    replace function calls when possible call in both irq/non-irq contexts
    
    Signed-off-by: Dmitry Kravkov <dmitry@...adcom.com>
    Signed-off-by: Eilon Greenstein <eilong@...adcom.com>
    Signed-off-by: David S. Miller <davem@...emloft.net>

diff --git a/drivers/net/bnx2x/bnx2x_cmn.c b/drivers/net/bnx2x/bnx2x_cmn.c
index 64d01e7..d5bd35b 100644
--- a/drivers/net/bnx2x/bnx2x_cmn.c
+++ b/drivers/net/bnx2x/bnx2x_cmn.c
@@ -131,7 +131,7 @@ static u16 bnx2x_free_tx_pkt(struct bnx2x *bp, struct bnx2x_fastpath *fp,
 
 	/* release skb */
 	WARN_ON(!skb);
-	dev_kfree_skb(skb);
+	dev_kfree_skb_any(skb);
 	tx_buf->first_bd = 0;
 	tx_buf->skb = NULL;
 
@@ -465,7 +465,7 @@ static void bnx2x_tpa_stop(struct bnx2x *bp, struct bnx2x_fastpath *fp,
 		} else {
 			DP(NETIF_MSG_RX_STATUS, "Failed to allocate new pages"
 			   " - dropping packet!\n");
-			dev_kfree_skb(skb);
+			dev_kfree_skb_any(skb);
 		}
 
 
diff --git a/drivers/net/bnx2x/bnx2x_cmn.h b/drivers/net/bnx2x/bnx2x_cmn.h
index fab161e..1a3545b 100644
--- a/drivers/net/bnx2x/bnx2x_cmn.h
+++ b/drivers/net/bnx2x/bnx2x_cmn.h
@@ -840,7 +840,7 @@ static inline int bnx2x_alloc_rx_skb(struct bnx2x *bp,
 	mapping = dma_map_single(&bp->pdev->dev, skb->data, fp->rx_buf_size,
 				 DMA_FROM_DEVICE);
 	if (unlikely(dma_mapping_error(&bp->pdev->dev, mapping))) {
-		dev_kfree_skb(skb);
+		dev_kfree_skb_any(skb);
 		return -ENOMEM;
 	}
 
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