On Thu, Dec 09, 2004 at 04:52:42PM -0500, Daniel Phillips wrote: > On Tuesday 07 December 2004 04:38, Patrick Caulfield wrote: > > On Mon, Dec 06, 2004 at 04:13:50PM -0800, Daniel McNeil wrote: > > > On Mon, 2004-12-06 at 11:45, Ken Preslan wrote: > > > > On Fri, Dec 03, 2004 at 03:08:00PM -0800, Daniel McNeil wrote: > > > > > > Looking at the stack trace above and dissabling dlm.ko, > > > it looks like dlm_lock+0x319 is the call to dlm_lock_stage1(). > > > looking at dlm_lock_stage1(), it looks like it is sleeping on > > > down_write(&rsb->res_lock) > > > > > > So now I have to find who is holding the res_lock. > > > > That's consistent with the hang you reported before - in fact it's > > almost certainly the same thing. My guess is thet there is a dealock > > on res_lock somewhere . In which case I suspect it's going to be > > easier to find that one by reading code rather than running tests. > > res_lock should never be held for any extended period of time, but in > > your last set of tracebacks there was nothing obviously holding it - > > so I suspect something is sleeping with it. > > Hi Patrick, > > Last week I had a bug in the cluster snapshot failover code that exposed > a bug in dlm or libdlm I think. My code inadvertently acquired a lock > twice, first in PW mode, then later in CR mode (because I wasn't > checking to see if it already had the PW lock). This caused > dlm_unlock_wait to wait forever. Are these locks supposed to be > recursive or not? In any event, waiting forever has got to be a bug. > > It might have something to do with a lkid tangle, since I never provided > separate lkids for the unlock. > > This should be easily reproducible. Thanks, I'll have a look at that. It's certainly a bug in your code that's causing it but, as you say, a hang in the library is still a bug in the library. If you call dlm_lock() with the same parameters twice then you will get two seperate locks - in that case the CR will wait for the PW to get out of the way. What is really confusing the issue is that both locks are sharing a lock status block - so it's possible that one lock is being marked INPROGRESS immediately after the first has completed, in that case the library will have a lot of difficulty in digging you out of your own hole I'm afraid as it can't disentangle the status of your two locks. Anyway, I'll see if I can see what's happening. -- patrick
