Hello, Joseph. Sorry about late reply.
On Wed, Feb 28, 2018 at 02:52:10PM +0800, Joseph Qi wrote: > In current code, I'm afraid pd_offline_fn() as well as the rest > destruction have to be called together under the same blkcg->lock and > q->queue_lock. > For example, if we split the pd_offline_fn() and radix_tree_delete() > into 2 phases, it may introduce a race between blkcg_deactivate_policy() > when exit queue and blkcg_css_free(), which will result in > pd_offline_fn() to be called twice. So, yeah, the sync scheme aroung blkg is pretty brittle and we'd need some restructuring to separate out blkg offlining and release, but it looks like that'd be the right thing to do, no? Thanks. -- tejun
