On Tue, 6 Mar 2012, Steven Rostedt wrote:
> Note, yesterday while running some stress tests I hit a live lock here:
> ...
> When it fails to grab either the inode->i_lock or the parent->d_lock it
> returns back to dput() and dput() will retry. We get into another one of
> these cases where we can spin blocking the holder of the locks.
Nasty.
> I experimented with adding a grab lock of the inode->i_lock or
> parent->d_lock if they existed (required initializing parent to NULL),
> which seemed to help a lot, but then eventually it locked up. As I'm not
> sure its safe to grab them straight here even after we release the
> dentry->d_lock. I'll have to enable full lockdep to see if this breaks
> the ordering.
>
> I haven't looked too deeply into this code yet, but I'm assuming that
> dput() can be called where we can't just take the inode or parent lock?
If you read the top of fs/dcache.c then you find an explanation of the
lock ordering. This code takes the locks in reverse order. That's why
it uses trylock.
Thanks,
tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
