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Subject: Re: [Bluez PATCH v1] input: disconnect intr channel before ctrl
 channel
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <CABBYNZ+=wMNuvjJ5VK2zpd6euqeEZ8JXbd67RmPgxDfdCgce9w@mail.gmail.com>
Date:   Wed, 18 Mar 2020 06:24:59 +0100
Cc:     Archie Pusaka <apusaka@google.com>,
        linux-bluetooth <linux-bluetooth@vger.kernel.org>
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References: <20200316123914.Bluez.v1.1.I2c83372de789a015c1ee506690bb795ee0b0b0d9@changeid>
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To:     Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Sender: linux-bluetooth-owner@vger.kernel.org
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Hi Luiz,

>> Luckily you asked, because I found out that actually the patch didn't
>> wait for the disconnection response for any case. It does delay the
>> disconnection of the ctrl channel slightly though, but that doesn't
>> guarantee a proper order of disconnection. Therefore, as of now, this
>> patch is not fixing anything.
>> 
>> Digging more into this matter, I found out by removing this condition
>> (sk->sk_shutdown == SHUTDOWN_MASK) in [1], it makes intr_watch_cb()
>> called after truly receiving the interrupt disconnection response.
>> However, I haven't checked whether removal of such condition will
>> break other things.
>> Do you have any suggestions?
> 
> I see, we shutdown the socket immediately since the socket API itself
> don't seem to have a concept of disconnect syscall not sure if other
> values could be passed to shutdown second parameter to indicate we
> want to actually wait it to be disconnected.

in a blocking synchronous system call world we have SO_LINGER for that. In the world of asynchronous IO handling (what we do), we need to check what is the right way of handling this.

Regards

Marcel