Messages in this thread |  | | Date | Fri, 23 Feb 2007 02:07:43 -0800 | From | Andrew Morton <> | Subject | Re: circular locking: /proc/sys/vm/drop_caches |
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> On Fri, 23 Feb 2007 07:35:38 +0100 Ingo Molnar <mingo@elte.hu> wrote: > i just got the lockdep warning below when doing: > > echo 3 > /proc/sys/vm/drop_caches > > is this a known quirk in the drop_caches code?
It is - we're taking inode_lock at just the wrong level there and I don't know how to fix it. The basic problem is that we're doing a list_head walk: if we drop the lock we have to start again.
Well, I do know how to fix it: rip the various inode lists and use a tagged radix tree instead - make writeback's per-superblock inode walk work the same as writeback's per-inode page walk. That will also alow us to drop the lock and then resume the drop_caches thing at the point where we left off.
But it's a large change and has some quite tricky issues which need to be carried over from the existing code and I don't have time to do it.
The only (lame) thing I can say for now is that drop_caches is a debug-only, root-only thing :(
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