netdev - Re: [syzbot] [net?] INFO: task hung in tls_sw

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Date:   Tue, 28 Feb 2023 14:51:32 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     syzbot <syzbot+9c0268252b8ef967c62e@...kaller.appspotmail.com>,
        borisp@...dia.com, bpf@...r.kernel.org, davem@...emloft.net,
        john.fastabend@...il.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] INFO: task hung in tls_sw_sendpage (3)

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..