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    SubjectRe: [PATCH 0/15] sysfs lazification final
    Greg KH <> writes:

    > On Mon, Nov 30, 2009 at 01:33:37PM -0800, Greg KH wrote:
    >> On Sat, Nov 07, 2009 at 11:25:03PM -0800, Eric W. Biederman wrote:
    >> >
    >> > The sysfs code updates the vfs caches immediately when the sysfs data
    >> > structures change causing a lot of unnecessary complications. The
    >> > following patchset untangles that beast. Allowing for simpler
    >> > more straight forward code, the removal of a hack from the vfs
    >> > to support sysfs, and human comprehensible locking on sysfs.
    >> >
    >> > Most of these patches have already been reviewed and acked from the
    >> > last time I had time to work on sysfs.
    >> >
    >> > This acks have been folded in and the two small bugs found in the
    >> > previous review have been fixed in the trailing patches (they are
    >> > minor enough nits that even a bisect that happens to land in the
    >> > middle should not see sysfs problems).
    >> I've applied all of these to my tree now, and sorry, but something is
    >> broken pretty badly.
    >> When doing a simple 'ls /sys/class/input/' the process locks up. This
    >> means that X can't find any input devices, which makes for a bit of a
    >> problem when wanting to use your mouse or keyboard :(
    >> Attached is the state of my processes when this happens, if that helps
    >> out any.
    >> So I'm going to drop all of these from my tree again, as they are not
    >> ready for merging at this point :(
    > In looking at the stuck processes, it seems your last patch was the
    > problem. Removing that caused things to work again, so I've only
    > dropped that one.
    > Next time, please test your patches before submitting them :(

    Weird I thought I had tested this.

    That last patch to add locking that is only needed for vfs coherency
    has certainly seen less testing than the others.

    I also remember verify that nfs does the same thing, when in fact
    nfs takes inode->i_lock not inode->i_mutex in the same situation.

    generic_permission takes no locks so this is really about serializing
    writes to the inode. The vfs only takes inode->i_mutex, when calling

    So it appears I have stepped into a murky corner of the vfs.

    I will take a look and do a bit more testing. At the moment it looks
    like a solution to serializing writes to the stat attributes on the inode is
    going to be simply holding sysfs_mutex over inode_setattr in
    sysfs_setattr. Assuming a solution is needed at all.


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