Re: [PATCH net v2 2/2] tuntap: correctly add the missing xdp flush
On 2018年02月22日 15:54, Sergei Shtylyov wrote:
Hello!
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
Silence.
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(),
Call.
a side effect is that this removes any possibility of batching which
could be addressed in the future.
Reported-by: Christoffer Dall
Fixes: 762c330d670e ("tuntap: add missing xdp flush")
Signed-off-by: Jason Wang
[...]
MBR, Sergei
My bad, let me post v3.
Thanks
Re: [PATCH net v2 2/2] tuntap: correctly add the missing xdp flush
Hello!
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
Silence.
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(),
Call.
a side effect is that this removes any possibility of batching which
could be addressed in the future.
Reported-by: Christoffer Dall
Fixes: 762c330d670e ("tuntap: add missing xdp flush")
Signed-off-by: Jason Wang
[...]
MBR, Sergei
[PATCH net v2 2/2] tuntap: correctly add the missing xdp flush
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
called under process context with preemption enabled. Simply disable
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
Fixes: 762c330d670e ("tuntap: add missing xdp flush")
Signed-off-by: Jason Wang
---
drivers/net/tun.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2823a4a..a363ea2 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1662,6 +1662,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct
*tun,
get_page(alloc_frag->page);
alloc_frag->offset += buflen;
err = xdp_do_redirect(tun->dev, , xdp_prog);
+ xdp_do_flush_map();
if (err)
goto err_redirect;
rcu_read_unlock();
--
2.7.4
