Eric Lee / linux-smarc-t335x-v3.2

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Commit 264524d5e5195f6e0f099bee20253a22b651e272

Authored by Heiko Carstens
Committed by David S. Miller
1 parent 6407d74c51
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

net: cpu offline cause napi stall 

Frank Blaschka reported :
<quote>
  During heavy network load we turn off/on cpus.
  Sometimes this causes a stall on the network device.
  Digging into the dump I found out following:

  napi is scheduled but does not run. From the I/O buffers
  and the napi state I see napi/rx_softirq processing has stopped
  because the budget was reached. napi stays in the
  softnet_data poll_list and the rx_softirq was raised again.

  I assume at this time the cpu offline comes in,
  the rx softirq is raised/moved to another cpu but napi stays in the
  poll_list of the softnet_data of the now offline cpu.

  Reviewing dev_cpu_callback (net/core/dev.c) I did not find the
  poll_list is transfered to the new cpu.
</quote>

This patch is a straightforward implementation of Frank suggestion :

Transfert poll_list and trigger NET_RX_SOFTIRQ on new cpu.

Reported-by: Frank Blaschka <blaschka@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Showing 1 changed file with 5 additions and 0 deletions Side-by-side Diff

... ... @@ -6178,6 +6178,11 @@
6178 6178 oldsd->output_queue = NULL;
6179 6179 oldsd->output_queue_tailp = &oldsd->output_queue;
6180 6180 }
  6181 + /* Append NAPI poll list from offline CPU. */
  6182 + if (!list_empty(&oldsd->poll_list)) {
  6183 + list_splice_init(&oldsd->poll_list, &sd->poll_list);
  6184 + raise_softirq_irqoff(NET_RX_SOFTIRQ);
  6185 + }
6181 6186  
6182 6187 raise_softirq_irqoff(NET_TX_SOFTIRQ);
6183 6188 local_irq_enable();