netdev - Re: [PATCH net] Revert "xsk: Do not sleep in poll() when need

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Message-ID: <e935822c-b2f6-8c62-8af7-4ce6e32ed4c3@iogearbox.net>
Date:   Tue, 4 Jan 2022 12:03:46 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org
Cc:     Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        bpf@...r.kernel.org
Subject: Re: [PATCH net] Revert "xsk: Do not sleep in poll() when need_wakeup
 set"

Hi Xuan,

On 1/4/22 10:57 AM, Xuan Zhuo wrote:
> This reverts commit bd0687c18e635b63233dc87f38058cd728802ab4.
> 
> When working with epoll, if the application encounters tx full, the
> application will enter epoll_wait and wait for tx to be awakened when
> there is room.
> 
> In the current situation, when tx is full pool->cached_need_wakeup may
> not be 0 (regardless of whether the driver supports wakeup, or whether
> the user uses XDP_USE_NEED_WAKEUP). The result is that if the user
> enters epoll_wait, because soock_poll_wait is not called, causing the
> user process to not be awakened.
> 
> Fixes: bd0687c18e63 ("xsk: Do not sleep in poll() when need_wakeup set")
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>

This is already reverted in net tree:

   https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=0706a78f31c4217ca144f630063ec9561a21548d

Thanks,
Daniel