Re: [PATCH 1/1] net: nps_enet: Disable interrupts before napi reschedule

From: Alexey Brodkin
Date: Thu May 26 2016 - 13:53:38 EST

Hi Elad,

On Thu, 2016-05-26 at 15:00 +-0300, Elad Kanfi wrote:
+AD4- From: Elad Kanfi
+AD4- Since NAPI works by shutting down event interrupts when theres
+AD4- work and turning them on when theres none, the net driver must
+AD4- make sure that interrupts are disabled when it reschedules polling.
+AD4- By calling napi+AF8-reschedule, the driver switches to polling mode,
+AD4- therefor there should be no interrupt interference.
+AD4- Any received packets will be handled in nps+AF8-enet+AF8-poll by polling the HW
+AD4- indication of received packet until all packets are handled.
+AD4- Signed-off-by: Elad Kanfi
+AD4- Acked-by: Noam Camus
+AD4- ---
+AD4- +AKA-drivers/net/ethernet/ezchip/nps+AF8-enet.c +AHwAoACgAKAAoA-4 +-+-+--
+AD4- +AKA-1 files changed, 3 insertions(+-), 1 deletions(-)
+AD4- diff --git a/drivers/net/ethernet/ezchip/nps+AF8-enet.c b/drivers/net/ethernet/ezchip/nps+AF8-enet.c
+AD4- index 085f912..06f0317 100644
+AD4- --- a/drivers/net/ethernet/ezchip/nps+AF8-enet.c
+AD4- +-+-+- b/drivers/net/ethernet/ezchip/nps+AF8-enet.c
+AD4- +AEAAQA- -205,8 +-205,10 +AEAAQA- static int nps+AF8-enet+AF8-poll(struct napi+AF8-struct +ACo-napi, int budget)
+AD4- +AKA- +AKAAKg- re-adding ourselves to the poll list.
+AD4- +AKA- +AKAAKg-/
+AD4- +AKA-
+AD4- - if (priv-+AD4-tx+AF8-skb +ACYAJg- +ACE-tx+AF8-ctrl+AF8-ct)
+AD4- +- if (priv-+AD4-tx+AF8-skb +ACYAJg- +ACE-tx+AF8-ctrl+AF8-ct) +AHs-
+AD4- +- nps+AF8-enet+AF8-reg+AF8-set(priv, NPS+AF8-ENET+AF8-REG+AF8-BUF+AF8-INT+AF8-ENABLE, 0)+ADs-
+AD4- +AKA- napi+AF8-reschedule(napi)+ADs-
+AD4- +- +AH0-
+AD4- +AKA- +AH0-
+AD4- +AKA-
+AD4- +AKA- return work+AF8-done+ADs-

We just bumped into the same problem (data exchange hangs on the very first +ACI-ping+ACI-)
with released Linux v4.6 and linux-next on our nSIM OSCI virtual platform.

I believe it was commit+AKA-05c00d82f4d1 (+ACI-net: nps+AF8-enet: bug fix - handle lost tx interrupts+ACI-)
that introduced the problem. At least reverting it I got networking working.

And indeed that patch fixes mentioned issue.
In other words...

Tested-by: Alexey Brodkin

P.S. Given my observation is correct please add following to your commit
message if you ever do a respin:
Fixes: 05c00d82f4d1 (+ACI-net: nps+AF8-enet: bug fix - handle lost tx interrupts+ACI-)

Cc: +ACM- 4.6.x