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From:   Philipp Reisner <philipp.reisner@linbit.com>
To:     David Laight <David.Laight@aculab.com>
Cc:     Jens Axboe <axboe@kernel.dk>,
        'Christoph =?ISO-8859-1?Q?B=F6hmwalder=27?= 
        <christoph.boehmwalder@linbit.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH] drbd: do not ignore signals in threads
Date:   Mon, 12 Aug 2019 15:28:40 +0200
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References: <20190729083248.30362-1-christoph.boehmwalder@linbit.com> <1761552.9xIroHqhk7@fat-tyre> <1fcbb94c5f264c17af3394807438ad50@AcuMS.aculab.com>
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Hi David,

[...]
> While our code is 'out of tree' (you really don't want it - and since
> it still uses force_sig() is fine) I suspect that the 'drdb' code
> (with Christoph's allow_signal() patch) now loops in kernel if a user
> sends it a signal.

I am not asking for that out of tree code. But you are welcome to learn
from the drbd code that is in the upstream kernel.
It does not loop if a root sends a signal, it receives it and ignores it.

> If the driver (eg drdb) is using (say) SIGINT to break a thread out of
> (say) a blocking kernel_accept() call then it can detect the unexpected
> signal (maybe double-checking with signal_pending()) but I don't think
> it can clear down the pending signal so that kernel_accept() blocks
> again.

You do that with flush_signals(current)

What we have do is, somewhere in the main loop:

  if (signal_pending(current)) {
			flush_signals(current);
			if (!terminate_condition()) {
				warn(connection, "Ignoring an unexpected signal\n");
				continue;
			}
			break;
		}
  }

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