|| ||Christoph Lameter <clameter-AT-sgi.com>|
|| ||Al Viro <viro-AT-ZenIV.linux.org.uk>|
|| ||Re: Major regression on hackbench with SLUB (more numbers)|
|| ||Wed, 26 Dec 2007 21:51:42 -0800 (PST)|
|| ||Theodore Tso <tytso-AT-mit.edu>, Andi Kleen <andi-AT-firstfloor.org>,
Willy Tarreau <w-AT-1wt.eu>, Steven Rostedt <rostedt-AT-goodmis.org>,
Linus Torvalds <torvalds-AT-linux-foundation.org>,
Ingo Molnar <mingo-AT-elte.hu>,
Peter Zijlstra <a.p.zijlstra-AT-chello.nl>,
Andrew Morton <akpm-AT-linux-foundation.org>,
Christoph Hellwig <hch-AT-infradead.org>,
"Rafael J. Wysocki" <rjw-AT-sisk.pl>|
On Wed, 26 Dec 2007, Al Viro wrote:
> Erm... Let me spell it out: current lifetime rules are completely broken.
> As it is, create/destroy/create cache sequence will do kobject_put() on
> kfree'd object. Even without people playing with holding sysfs files
> open or doing IO on those.
Urgh. Help! Isnt there some sanity with sysfs?
> a) you have kobject embedded into struct with the lifetime rules of its
> own. When its refcount hits zero you kfree() the sucker, even if you
> still have references to embedded kobject.
So alloate it separately?
> b) your symlinks stick around. Even when cache is long gone you still
> have a sysfs symlink with its embedded kobject as a target. They are
> eventually removed when cache with the same name gets created. _Then_
> you get the target kobject dropped - when the memory it used to be in
> had been freed for hell knows how long and reused by something that would
> not appreciate slub.c code suddenly deciding to decrement some word in
> that memory.
Hmmmm.. That would also be addressed by a having a separately allocated
> c) you leak references to these kobject; kobject_del() only removes it
> from the tree undoing the effect of kobject_add() and you still need
> kobject_put() to deal with the last reference.
Patches would be appreciated.... Had a hard time to get the sysfs support
to work right.
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