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Subject: Re: svn commit: r339582 - head/sys/dev/sound/midi
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
References: <201810220858.w9M8wSBZ039042@repo.freebsd.org>
 <20181022095131.GN5335@kib.kiev.ua>
From: Hans Petter Selasky <hps@selasky.org>
Message-ID: <cc0210c5-99c7-1153-0b32-4cfdc576970a@selasky.org>
Date: Mon, 22 Oct 2018 12:09:54 +0200
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On 10/22/18 11:51 AM, Konstantin Belousov wrote:
> On Mon, Oct 22, 2018 at 08:58:28AM +0000, Hans Petter Selasky wrote:
>> Author: hselasky
>> Date: Mon Oct 22 08:58:27 2018
>> New Revision: 339582
>> URL: https://svnweb.freebsd.org/changeset/base/339582
>>
>> Log:
>>    Drop sequencer mutex around uiomove() and make sure we don't move more bytes
>>    than is available, else a panic might happen.
> And why it is safe to drop the mutex ?
> If it is safe to drop, why do you need the mutex at all ?
> 

The seq mutex protects the queue state, which is entirely computed prior 
or after uiomove().

--HPS