netdev - [RFC PATCH net 2/2] amd-xgbe: Avoid sleeping in napi

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Date:   Tue, 15 Oct 2019 14:49:11 +0100
From:   James Morse <james.morse@....com>
To:     netdev@...r.kernel.org
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        "Dave S . Miller" <davem@...emloft.net>
Subject: [RFC PATCH net 2/2] amd-xgbe: Avoid sleeping in napi_disable() while holding a spinlock

xgbe_powerdown() takes an irqsave spinlock, then calls napi_disable()
via xgbe_napi_disable(). napi_disable() might call msleep().
DEBUG_ATOMIC_SLEEP isn't happy about this:
| BUG: sleeping function called from invalid context at ../net/core/dev.c:6332
| in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 2831, name: bash
| CPU: 3 PID: 2831 Comm: bash Tainted: G        W         5.4.0-rc3-00001-g9dbe793f263b #114
| Hardware name: AMD Seattle (Rev.B0) Development Board (Overdrive) (DT)
| Call trace:
|  dump_backtrace+0x0/0x160
|  show_stack+0x24/0x30
|  dump_stack+0xb0/0xf8
|  ___might_sleep+0x124/0x148
|  __might_sleep+0x54/0x90
|  napi_disable+0x48/0x140
|  xgbe_napi_disable+0x64/0xc0
|  xgbe_powerdown+0xb0/0x120
|  xgbe_platform_suspend+0x34/0x80
|  pm_generic_freeze+0x3c/0x58
|  acpi_subsys_freeze+0x2c/0x38
|  dpm_run_callback+0x3c/0x1e8
|  __device_suspend+0x130/0x468
|  dpm_suspend+0x114/0x388
|  hibernation_snapshot+0xe8/0x378
|  hibernate+0x18c/0x2f8

Move xgbe_napi_disable() outside the spin_lock()d region of
xgbe_powerdown(). This matches its use in xgbe_stop() ... but this
might only be safe because of the earlier call to xgbe_free_irqs().

Signed-off-by: James Morse <james.morse@....com>

---
RFC as I'm not familiar with this driver. I'm happy to test a better fix!
---
 drivers/net/ethernet/amd/xgbe/xgbe-drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
index bfba7effcf9f..a6e6c21e921f 100644
--- a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
@@ -1278,10 +1278,10 @@ int xgbe_powerdown(struct net_device *netdev, unsigned int caller)
 	hw_if->powerdown_tx(pdata);
 	hw_if->powerdown_rx(pdata);
 
-	xgbe_napi_disable(pdata, 0);
-
 	spin_unlock_irqrestore(&pdata->lock, flags);
 
+	xgbe_napi_disable(pdata, 0);
+
 	DBGPR("<--xgbe_powerdown\n");
 
 	return 0;
-- 
2.20.1