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lantiq: fix sleep with spinlock held in xrx200 network driver

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In the xrx200_close() function we call napi_disable(), that could
sleep, with priv->hw->chan[i].lock held. This could lead to deadlock
and causes the kernel to complain.

Look at the code I couldn't convince myself about why we
need to protect that specific code part with the lock. IMHO there
seems no reason to protect the refcount variables, because AFAIK
ndo_close() and ndo_open() callbacks are already called with a
semaphore held. Neither I could figure out why napi_disable() have to
be called with that lock held. The only remaining code part for
which I could guess the lock is useful for is ltq_dma_close()
function call.

This patch reduces the lock to the said function call, avoiding the
sleep-with-spinlock-held situation

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
[fold into 0025-NET-MIPS-lantiq-adds-xrx200-net.patch, backport to
kernel 4.4]
Signed-off-by: Mathias Kresin <dev@kresin.me>
This commit is contained in:
Andrea Merello 2017-07-08 10:11:11 +02:00 committed by Mathias Kresin
parent 34c01e68b5
commit b81c04382b
2 changed files with 8 additions and 6 deletions
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7
target/linux/lantiq/patches-4.4/0025-NET-MIPS-lantiq-adds-xrx200-net.patch
View file

@ -209,7 +209,7 @@ Subject: [PATCH 25/36] NET: MIPS: lantiq: adds xrx200-net
+};
--- /dev/null
+++ b/drivers/net/ethernet/lantiq_xrx200.c
@@ -0,0 +1,1852 @@
@@ -0,0 +1,1853 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
@ -1110,14 +1110,15 @@ Subject: [PATCH 25/36] NET: MIPS: lantiq: adds xrx200-net
+ for (i = 0; i < XRX200_MAX_DMA; i++) {
+ if (!priv->hw->chan[i].dma.irq)
+ continue;
+ spin_lock_bh(&priv->hw->chan[i].lock);
+
+ priv->hw->chan[i].refcount--;
+ if (!priv->hw->chan[i].refcount) {
+ if (XRX200_DMA_IS_RX(i))
+ napi_disable(&priv->hw->chan[i].napi);
+ spin_lock_bh(&priv->hw->chan[i].lock);
+ ltq_dma_close(&priv->hw->chan[XRX200_DMA_RX].dma);
+ spin_unlock_bh(&priv->hw->chan[i].lock);
+ }
+ spin_unlock_bh(&priv->hw->chan[i].lock);
+ }
+
+ return 0;

7
target/linux/lantiq/patches-4.9/0025-NET-MIPS-lantiq-adds-xrx200-net.patch
View file

@ -209,7 +209,7 @@ Subject: [PATCH 25/36] NET: MIPS: lantiq: adds xrx200-net
+};
--- /dev/null
+++ b/drivers/net/ethernet/lantiq_xrx200.c
@@ -0,0 +1,1851 @@
@@ -0,0 +1,1852 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
@ -1110,14 +1110,15 @@ Subject: [PATCH 25/36] NET: MIPS: lantiq: adds xrx200-net
+ for (i = 0; i < XRX200_MAX_DMA; i++) {
+ if (!priv->hw->chan[i].dma.irq)
+ continue;
+ spin_lock_bh(&priv->hw->chan[i].lock);
+
+ priv->hw->chan[i].refcount--;
+ if (!priv->hw->chan[i].refcount) {
+ if (XRX200_DMA_IS_RX(i))
+ napi_disable(&priv->hw->chan[i].napi);
+ spin_lock_bh(&priv->hw->chan[i].lock);
+ ltq_dma_close(&priv->hw->chan[XRX200_DMA_RX].dma);
+ spin_unlock_bh(&priv->hw->chan[i].lock);
+ }
+ spin_unlock_bh(&priv->hw->chan[i].lock);
+ }
+
+ return 0;