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Date: Wed, 8 Nov 2023 17:52:15 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: "Nelson, Shannon" <shannon.nelson@amd.com>
Cc: Toke =?UTF-8?B?SMO4aWxhbmQtSsO4cmdlbnNlbg==?= <toke@redhat.com>, Jesper
 Dangaard Brouer <hawk@kernel.org>, David Ahern <dsahern@gmail.com>,
 netdev@vger.kernel.org, bpf@vger.kernel.org, Daniel Borkmann
 <daniel@iogearbox.net>, Alexei Starovoitov <ast@kernel.org>, Andrii
 Nakryiko <andrii@kernel.org>
Subject: Re: BPF/XDP: kernel panic when removing an interface that is an
 xdp_redirect target
Message-ID: <20231108175215.351d22bf@kernel.org>
In-Reply-To: <fa95d5d0-35c0-497e-aea8-a35f9f6304f4@amd.com>
References: <e3085c47-7452-4302-8401-1bda052a3714@amd.com>
	<87h6lxy3zq.fsf@toke.dk>
	<fa95d5d0-35c0-497e-aea8-a35f9f6304f4@amd.com>
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On Wed, 8 Nov 2023 13:30:21 -0800 Nelson, Shannon wrote:
> > Another source of a bug like this could be that your driver does not in
> > fact call xdp_do_flush() before exiting its NAPI cycle, so that there
> > will be packets from the previous cycle in the bq queue, in which case
> > the assumption mentioned in the linked document obviously breaks down.
> > But that would also be a driver bug :)  
> 
> We do call the xdp_do_flush() at the end of the NAPI cycle, just before 
> calling napi_complete_done().

Just to be sure - flush has to happen on every cycle, not only
before calling napi_complete_done().