Re: circular locking: /proc/sys/vm/drop_caches

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



> On Fri, 23 Feb 2007 07:35:38 +0100 Ingo Molnar <[email protected]> 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 :(

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux