On Tue, Apr 27, 2010 at 05:40:53PM +0300, Benny Halevy wrote: > Bruce, Oddly enough I didn't receive the patch you're commenting on into > my inbox. It already happened before on this list and I've no idea what > could have went wrong. (I also have a gmail account subscribed on this list > and I can't find it there, even in the spam folder :-/) Huh. I see it in various archives, so I'll assume the problem's on your end. > comments below... > > On Apr. 24, 2010, 0:24 +0300, "J. Bruce Fields" <bfields@xxxxxxxxxxxxxx> wrote: > > Benny--I coded up a simple (possibly incorrect) implementation of this, > > and then remembered that this was more or less what your > > state-lock-reduction-prep patch series did. Do you have a more recent > > version of those patches? > > Yup. though untested with latest bits. > I'll resend it as a reply to this message. I think what we actually want is a mechanism with semantics like yours, but with multiple RENEW values so we can track how many users there are and have only the last one do the renew. One possibility: - add a cl_users field, with: cl_user>0 meaning: somebody's using this client right now, don't expire it. (Your RENEW state.) cl_user<0 meaning: this client is already being expired, don't try to use it (or any sessionid or other state associated with it). (Your EXPIRED state.) cl_user==0: fair game to either use or (if expiry time has passed) to expire. (Your NORMAL state.) - add a cl_renewme boolean, meaning: last user of this client (user to decrement to 0) should renew the client (reset the expiry time and move it to the back of the lru). So: - in laundromat: - atomically check whether cl_users is 0, and, if so, decrement to -1. (If positive, skip expiring this client.) - on looking up a sessionid (or, eventually, any state object associated with a client), call get_client(), which: - atomically checks whether cl_users is >=0, and, if so, increments it. If <0, fail to find the object and return an appropriate error (STALE?). - on renew: - BUG_ON(cl_user<=0) - set cl_renewme - on dropping reference to a sessionid (or, eventually, any state object associated with a client), call put_client(), which: - atomically decrements cl_users, checks whether it hits zero, and (if so, and if cl_renewme set), renews the client. One possible implementation: make cl_users atomic, add a per-client spinlock, make the put_client() do an atomic_dec_and_lock(), etc. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
