From: Andi Kleen <andi@firstfloor.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Christoph Hellwig <hch@infradead.org>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
Andi Kleen <ak@linux.intel.com>,
xfs-masters@oss.sgi.com
Subject: Re: [PATCH 05/13] XFS: Fix lock ASSERT on UP
Date: Fri, 30 Mar 2012 16:04:57 +0200 [thread overview]
Message-ID: <20120330140457.GH17822@one.firstfloor.org> (raw)
In-Reply-To: <20120330041348.GF18323@dastard>
On Fri, Mar 30, 2012 at 03:13:48PM +1100, Dave Chinner wrote:
> On Fri, Mar 30, 2012 at 01:52:01AM +0200, Andi Kleen wrote:
> > On Thu, Mar 29, 2012 at 07:21:14PM -0400, Christoph Hellwig wrote:
> > > On Tue, Mar 27, 2012 at 05:47:09PM -0700, Andi Kleen wrote:
> > > > From: Andi Kleen <ak@linux.intel.com>
> > > >
> > > > ASSERT(!spin_is_locked()) doesn't work on UP builds. Replace with a standard
> > > > lockdep_assert_held()
> > >
> > > The "standard" is assert_spin_locked() - which not only is much cheaper
> > > but also has the advantage of working in non-lockdep builds.
> >
> > But then you have it unconditional, not just on debug builds.
>
> And the problem with that is what? There is so little overhead to the
> check it doesn't matter that it is enabled in production kernels...
It's really interesting how much you guys argue for your buggy construct
which you clearly never tested on a UP build...
Not sure if that is a hot path, but on highly contended locks every cache line
fetch is quite expensive on larger systems.
also I doubt the thing really catches bugs, and if it did you would be
probably better off with a sparse notation or so.
Anyways I will turn it into the normal assert.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2012-03-30 14:05 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-28 0:47 spin-is-locked is evil patchkit v2 Andi Kleen
2012-03-28 0:47 ` [PATCH 01/13] block: use lockdep_assert_held for queue locking Andi Kleen
2012-03-30 10:33 ` Jens Axboe
2012-03-28 0:47 ` [PATCH 02/13] sgi-xp: Use lockdep_assert_held Andi Kleen
2012-03-28 0:47 ` [PATCH 03/13] ada152x: Remove broken usage of spin_is_locked Andi Kleen
2012-03-28 0:47 ` [PATCH 04/13] staging/zmem: Use lockdep_assert_held instead " Andi Kleen
2012-03-28 0:47 ` [PATCH 05/13] XFS: Fix lock ASSERT on UP Andi Kleen
2012-03-29 23:21 ` Christoph Hellwig
2012-03-29 23:52 ` Andi Kleen
2012-03-30 4:13 ` Dave Chinner
2012-03-30 14:04 ` Andi Kleen [this message]
2012-03-30 14:10 ` Christoph Hellwig
2012-04-19 21:31 ` Andrew Morton
2012-03-28 0:47 ` [PATCH 06/13] huge-memory: Use lockdep_assert_held Andi Kleen
2012-03-28 0:47 ` [PATCH 07/13] futex: Use lockdep_assert_held() for lock checking Andi Kleen
2012-03-28 0:47 ` [PATCH 08/13] irda: remove spin_is_locked Andi Kleen
2012-03-28 1:32 ` David Miller
2012-03-28 0:47 ` [PATCH 09/13] usb: gadget: f_fs: Remove lock is held before freeing checks Andi Kleen
2012-04-10 10:42 ` Felipe Balbi
2012-03-28 0:47 ` [PATCH 10/13] smsc911x: Use lockdep_assert_held instead of home grown buggy construct Andi Kleen
2012-03-28 1:32 ` David Miller
2012-03-28 0:47 ` [PATCH 11/13] Add a discussion on why spin_is_locked() is bad to spinlocks.txt Andi Kleen
2012-03-28 8:48 ` Wolfram Sang
2012-03-28 9:07 ` Andi Kleen
2012-03-28 0:47 ` [PATCH 12/13] Add a kerneldoc comment to spin_is_locked() that discourages its usage Andi Kleen
2012-03-28 8:49 ` Wolfram Sang
2012-03-28 0:47 ` [PATCH 13/13] checkpatch: Check for spin_is_locked Andi Kleen
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