Date:   Tue, 28 Feb 2023 14:51:32 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Eric Dumazet <edumazet@google.com>
Cc:     syzbot <syzbot+9c0268252b8ef967c62e@syzkaller.appspotmail.com>,
        borisp@nvidia.com, bpf@vger.kernel.org, davem@davemloft.net,
        john.fastabend@gmail.com, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, pabeni@redhat.com,
        syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [net?] INFO: task hung in tls_sw_sendpage (3)
Message-ID: <20230228145132.6d09453f@kernel.org>
In-Reply-To: <CANn89i+ooMT_G9aL8keZ-WOcAKqpC44OLQNGvfUtjA6PW-yxcA@mail.gmail.com>
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        <CANn89iJ_kLaF0tVVUfzKQwVkQ0VtCca1dL8eF+RrXCVDTK6h2Q@mail.gmail.com>
        <20230227155352.3399bb10@kernel.org>
        <CANn89i+ooMT_G9aL8keZ-WOcAKqpC44OLQNGvfUtjA6PW-yxcA@mail.gmail.com>
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On Tue, 28 Feb 2023 12:23:46 +0100 Eric Dumazet wrote:
> This report mentions sendpage, but sendmsg() would have the same issue.
> 
> A thread might be blocked in sk_stream_wait_memory() with the mutex
> held, for an arbitrary amount of time,
> say if the remote peer stays in RWIN 0 for hours.
> 
> This prevents tx_work from making progress, and
> tls_sw_cancel_work_tx() would be stuck forever.
> 
> The consensus is that the kernel shouts a warning if a thread has been
> waiting on a mutex
> more than 120 seconds (check_hung_uninterruptible_tasks())

Thanks for explaining, let's see if I can hack a fix together..