|From:||Christoph Lameter <clameter-AT-sgi.com>|
|To:||Al Viro <viro-AT-ZenIV.linux.org.uk>|
|Subject:||Re: Major regression on hackbench with SLUB (more numbers)|
|Date:||Wed, 26 Dec 2007 21:51:42 -0800 (PST)|
|Cc:||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>, LKML <linux-kernel-AT-vger.kernel.org>, 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 kobject? > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to firstname.lastname@example.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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