Re: [PATCH net] ixgbe: check return value of napi_complete_done()

On 09/20/2018 12:01 PM, Song Liu wrote:

The NIC driver should only enable interrupts when napi_complete_done()
returns true. This patch adds the check for ixgbe.

Cc: stable@vger.kernel.org # 4.10+
Cc: Jeff Kirsher <redacted>
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Song Liu <redacted>
---

Well, unfortunately we do not know why this is needed,
this is why I have not yet sent this patch formally.

netpoll has correct synchronization :

poll_napi() places into napi->poll_owner current cpu number before calling poll_one_napi()

netpoll_poll_lock() does also use napi->poll_owner

When netpoll calls ixgbe poll() method, it passed a budget of 0,
meaning napi_complete_done() is not called.

As long as we can not explain the problem properly in the changelog,
we should investigate, otherwise we will probably see coming dozens of patches
trying to fix a 'potential hazard'.

Thanks.