On Fri, Jul 8, 2016 at 9:03 AM, George Wilson <george.wil...@delphix.com> wrote:
> Andriy, > > I think this is basically a rule, although I don't think it's stated > anywhere. We do rely heavily on this locking strategy since there are many > places that will hold the namespace lock to prevent spa config changes but > yet wait for a txg to sync. > > Is it honored everywhere? Well, I hope so but there probably hasn't been a > detailed analysis done to see if there might be places where we do > something like a spa_open() from some obscure path in the sync thread. I > would hope that our testing would have discovered that quickly and > hopefully developers will sufficiently exercise their code to make sure > they don't violate this. > > Have you seen instances where we deadlock as a result of this? > > Thanks, > George > > Waiting for txg sync while holding spa_namespace_lock can lead to an unecoverable state if the pool I/O gets suspended. I've seen this with a failed import where spa_config_update is blocked: https://www.illumos.org/issues/2607 -Albert > On Fri, Jul 8, 2016 at 9:40 AM, Andriy Gapon <a...@freebsd.org> wrote: > >> >> I see a few places in the code that do the following: >> mutex_enter(&spa_namespace_lock); >> dsl_sync_task(...); >> mutex_exit(&spa_namespace_lock); >> One example is spa_change_guid(). >> >> In my understanding this implies that the sync thread must never acquire >> spa_namespace_lock. Is this a real rule? Do we always honor it? >> >> Thank you! >> -- >> Andriy Gapon >> >> >> http://www.listbox.com >> > > *openzfs-developer* | Archives > <https://www.listbox.com/member/archive/274414/=now> > <https://www.listbox.com/member/archive/rss/274414/28015425-16c03b8c> | > Modify > <https://www.listbox.com/member/?&;> > Your Subscription <http://www.listbox.com> > ------------------------------------------- openzfs-developer Archives: https://www.listbox.com/member/archive/274414/=now RSS Feed: https://www.listbox.com/member/archive/rss/274414/28015062-cce53afa Modify Your Subscription: https://www.listbox.com/member/?member_id=28015062&id_secret=28015062-f966d51c Powered by Listbox: http://www.listbox.com
