Peter Zijlstra 3c8ed88974 kref: Remove the memory barriers ... Commit 1b0b3b9980 ("kref: fix CPU ordering with respect to krefs") wrongly adds memory barriers to kref. It states: some atomic operations are only atomic, not ordered. Thus a CPU is allowed to reorder memory references to an object to before the reference is obtained. This fixes it. While true, it fails to show why this is a problem. I say it is not a problem because if there is a race with kref_put() such that we could end up referencing a free'd object without this memory barrier, we would still have that race with the memory barrier. The kref_put() in question could complete (and free the object) before the atomic_inc() and we'd still be up shit creek. The kref_init() case is even worse, if your object is published at this time you're so wrong the memory barrier won't make a difference what so ever. If its not published, the act of publishing should include the needed barriers/locks to make sure all writes prior to the act of publishing are complete such that others will only observe a complete object. Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Oliver Neukum <oneukum@suse.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>		2011-12-13 09:11:19 -08:00
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acpi	Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux	2011-11-07 10:13:52 -08:00
asm-generic	Merge Qualcom Hexagon architecture	2011-11-01 07:48:13 -07:00
crypto	crypto: Add a report function pointer to crypto_type	2011-10-21 14:24:03 +02:00
drm	Merge branch 'drm-fixes' of git://people.freedesktop.org/~airlied/linux	2011-11-07 10:01:56 -08:00
keys	…
linux	kref: Remove the memory barriers	2011-12-13 09:11:19 -08:00
math-emu	…
media	Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux	2011-11-06 19:44:47 -08:00
misc	[media] altera-stapl: it is time to move out from staging	2011-09-23 15:00:57 -03:00
mtd	mtd: kill old field for `struct mtd_info_user'	2011-09-11 15:57:44 +03:00
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2011-11-07 10:55:33 -08:00
pcmcia	…
rdma	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband	2011-11-01 10:51:38 -07:00
rxrpc	…
scsi	Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6	2011-10-28 16:44:18 -07:00
sound	Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux	2011-11-06 19:44:47 -08:00
target	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending	2011-11-06 19:00:42 -08:00
trace	Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux	2011-11-06 19:44:47 -08:00
video	Merge branch 'for-florian' of git://gitorious.org/linux-omap-dss2/linux into fbdev-next	2011-10-15 00:19:52 +00:00
xen	Merge branch 'upstream/xen-settime' of git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen	2011-11-06 20:15:05 -08:00
Kbuild	…