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Date: Mon, 29 Aug 2011 23:11:03 +0800
Message-ID: <CAF1ivSYu=0Xh3aXJGbuBUZjT_azLTO6Tq1gzhNRBWsHXCUMjiw@mail.gmail.com>
Subject: Re: blkdev_issue_discard() hangs forever if the underlying storage
 device is removed
From: Lin Ming <lxy@ss.pku.edu.cn>
To: Lukas Czerner <lczerner@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>, Jens Axboe <jaxboe@fusionio.com>,
        Mike Snitzer <snitzer@redhat.com>, LKML <linux-kernel@vger.kernel.org>
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On Mon, Aug 29, 2011 at 10:42 PM, Lukas Czerner <lczerner@redhat.com> wrote:
> On Mon, 29 Aug 2011, Lin Ming wrote:
>
>> On Mon, Aug 29, 2011 at 7:56 PM, Lukas Czerner <lczerner@redhat.com> wrote:
>> >
>> > Regarding the atomic operations I do not think that implicit memory
>> > barriers are needed here as atomic_dec_and_test() implies memory
>>
>> Which implicit memory barrier you are talking about?
>
> smp_mb() at both side of the operation as documented here in
> Documentation/memory-barriers.txt

Thanks for the info.

But I don't follow you ... why that implicit memory barriers are NOT needed?