On 2018年02月22日 15:54, Sergei Shtylyov wrote:

On 2/22/2018 9:24 AM, Jason Wang wrote:

Commit 762c330d670e ("tuntap: add missing xdp flush") tries to fix the
devmap stall caused by missed xdp flush by counting the pending xdp
redirected packets and flush when it exceeds NAPI_POLL_WEIGHT or
MSG_MORE is clear. This may lead BUG() since xdp_do_flush() was

   Lead to BUG().

called under process context with preemption enabled. Simply disable

   s/under/in the/?

preemption may silent the warning but be not enough since process may


move between different CPUS during a batch which cause xdp_do_flush()
misses some CPU where the process run previously. Consider the several
fallouts, that commit was reverted. To fix the issue correctly, we can
simply calling xdp_do_flush() immediately after xdp_do_redirect(),


a side effect is that this removes any possibility of batching which
could be addressed in the future.

Reported-by: Christoffer Dall <christoffer.d...@linaro.org>
Fixes: 762c330d670e ("tuntap: add missing xdp flush")
Signed-off-by: Jason Wang <jasow...@redhat.com>

MBR, Sergei

My bad, let me post v3.


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