From: "H. Peter Anvin" <hpa@zytor.com>
To: Anton Altaparmakov <aia21@cantab.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] 2.5.21 Nonlinear CPU support
Date: Wed, 12 Jun 2002 15:21:43 -0700 [thread overview]
Message-ID: <3D07C977.7090603@zytor.com> (raw)
In-Reply-To: <5.1.0.14.2.20020612155646.048fd520@pop.cus.cam.ac.uk> <5.1.0.14.2.20020611155046.00af3980@pop.cus.cam.ac.uk> <5.1.0.14.2.20020612155646.048fd520@pop.cus.cam.ac.uk> <5.1.0.14.2.20020612192802.045b08c0@pop.cus.cam.ac.uk> <5.1.0.14.2.20020612214327.04590b70@pop.cus.cam.ac.uk>
Anton Altaparmakov wrote:
>>
>> Note that there is no requirement that we're still on cpu "cpu" when
>> we allocate the buffer. Furthermore, if we fail, we just loop right
>> back to the top.
>
>
> What is the point though? Why not just:
>
> if (!unlikely(decompression_buffers)) {
> down_sem();
> allocate_decompression_buffers();
> up_sem();
> }
>
> And be done with it?
>
> I don't see any justification for the increased complexity...
>
Race condition -- you have to drop out of the critical section before
you grab the allocation sempahore, and another CPU can grab the
semaphore in that time.
Thus, the buffers might appear right under your nose.
-hpa
next prev parent reply other threads:[~2002-06-12 22:22 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-11 7:08 [PATCH] 2.5.21 Nonlinear CPU support Rusty Russell
2002-06-11 7:42 ` Andrew Morton
2002-06-11 9:09 ` Rusty Russell
2002-06-11 9:10 ` David S. Miller
2002-06-12 6:58 ` Rusty Russell
2002-06-12 9:26 ` David S. Miller
2002-06-13 5:01 ` Rusty Russell
2002-06-13 5:55 ` David S. Miller
2002-06-11 9:27 ` Andrew Morton
2002-06-11 11:22 ` Anton Altaparmakov
2002-06-12 5:57 ` Rusty Russell
2002-06-12 7:54 ` Anton Altaparmakov
2002-06-12 8:06 ` Rusty Russell
2002-06-12 8:25 ` Anton Altaparmakov
2002-06-12 19:32 ` Linus Torvalds
2002-06-12 13:10 ` Mikael Pettersson
2002-06-13 2:42 ` Rusty Russell
2002-06-12 0:53 ` Rusty Russell
2002-06-12 8:36 ` Helge Hafting
2002-06-11 10:57 ` Anton Altaparmakov
2002-06-11 17:59 ` Robert Love
2002-06-12 4:11 ` Rusty Russell
2002-06-11 19:29 ` Denis Vlasenko
2002-06-11 14:54 ` Anton Altaparmakov
2002-06-12 19:32 ` Denis Vlasenko
2002-06-12 15:08 ` Anton Altaparmakov
2002-06-12 17:36 ` Andreas Dilger
2002-06-12 18:34 ` Anton Altaparmakov
2002-06-12 19:39 ` Andreas Dilger
2002-06-12 20:41 ` Anton Altaparmakov
2002-06-12 21:03 ` Andreas Dilger
2002-06-12 21:15 ` Anton Altaparmakov
2002-06-12 20:03 ` H. Peter Anvin
2002-06-12 20:54 ` Robert Love
2002-06-12 20:57 ` Anton Altaparmakov
2002-06-12 22:21 ` H. Peter Anvin [this message]
2002-06-13 1:33 ` Anton Altaparmakov
2002-06-13 1:38 ` H. Peter Anvin
2002-06-13 1:45 ` Anton Altaparmakov
2002-06-13 2:13 ` H. Peter Anvin
2002-06-13 2:21 ` Anton Altaparmakov
2002-06-13 8:43 ` Helge Hafting
2002-06-11 18:01 ` Robert Love
2002-06-12 7:57 ` Alan Cox
2002-06-12 8:01 ` Rusty Russell
[not found] <Pine.LNX.4.33.0206121226550.1533-100000@penguin.transmeta. com>
2002-06-12 21:29 ` Anton Altaparmakov
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