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From: Markus Armbruster <armbru@redhat.com>
References: <20181029125733.14597-1-marcandre.lureau@redhat.com>
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Date: Mon, 03 Dec 2018 10:29:39 +0100
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	(=?utf-8?Q?=22Marc-Andr=C3=A9?= Lureau"'s message of "Mon, 3 Dec 2018
	12:04:00 +0400")
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Subject: Re: [Qemu-devel] [PATCH v2 2/6] monitor: accept chardev input from
 iothread
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To: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau <marcandre.lureau@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, QEMU <qemu-devel@nongnu.org>, Peter Xu <peterx@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Marc-Andr=C3=A9 Lureau <marcandre.lureau@gmail.com> writes:

> Hi
>
> On Mon, Dec 3, 2018 at 11:26 AM Markus Armbruster <armbru@redhat.com> wro=
te:
>>
>> Marc-Andr=C3=A9 Lureau <marcandre.lureau@redhat.com> writes:
>>
>> > Chardev backends may not handle safely IO events from concurrent
>> > threads.
>>
>> What exactly could go wrong?  Or is this a well-known fact that doesn't
>> need further elaboration?
>
> chardev are not thread-safe. Only the write path is, since commit
> 9005b2a7589540a3733b3abdcfbccfe7746cd1a1.

Add this to your commit message?  Your call.

>> "safely handle I/O events"
>>
>> >          Better to wake up the chardev from the monitor IO thread if
>> > it's being used as the chardev context.
>> >
>> > Unify code paths by using a BH in all cases.
>> >
>> > Drop the now redundant aio_notify() call.
>> >
>> > Signed-off-by: Marc-Andr=C3=A9 Lureau <marcandre.lureau@redhat.com>
[...]