From: Christoph Hellwig <hch@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Dave Chinner <david@fromorbit.com>,
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 10:10:59 -0400 [thread overview]
Message-ID: <20120330141058.GA19986@infradead.org> (raw)
In-Reply-To: <20120330140457.GH17822@one.firstfloor.org>
On Fri, Mar 30, 2012 at 04:04:57PM +0200, Andi Kleen wrote:
> It's really interesting how much you guys argue for your buggy construct
> which you clearly never tested on a UP build...
spin_is_locked always return 0 on UP builds, and given that XFS only
has !spin_is_locked asserts things will work just fine on UP builds
(not the !CONFIG_SMP and !CONFIG_XFS_DEBUG would be a common
combination).
In fact if you check the archives the one use of assert_spin_locked was
added exactly because some still tripped over the spin_is_locked
behaviour on UP relatively soon.
> Not sure if that is a hot path, but on highly contended locks every cache line
> fetch is quite expensive on larger systems.
It's not an overly contended lock.
> also I doubt the thing really catches bugs, and if it did you would be
> probably better off with a sparse notation or so.
This one probably doesn't - the first occurance is just after a blocking
allocation, and the second one just before taking the lock. So they
probably could as well just be removed.
The point that still stands is that lockdep_assert_held isn't actually
a useful replacement.
next prev parent reply other threads:[~2012-03-30 14:11 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
2012-03-30 14:10 ` Christoph Hellwig [this message]
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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