On Tue, Jan 25, 2011 at 08:01:00PM +0000, Steve Little wrote: > I've been trying to make use of deadlock detection in libdlm, but > without any luck so far. I'm hoping someone can tell me what I'm doing > wrong, or how to debug this further. The dlm detects *conversion* deadlocks on a single resource and returns EDEADLK for them. > This should cause a classic deadlock: process 1 is waiting on resource > A, which is locked by process 2. Process 2 is waiting on resource B, > which is locked by process 1. A "classic" multi-resource deadlock is not detected. Google came up with this nice description of the difference: http://books.google.com/books?id=ydKIsgCiFVsC&pg=PA143&lpg=PA143&dq=conversion+deadlock&source=bl&ots=LSJEUQU3HI&sig=eo4UhF9sR474OvQ1Nbeid2iHTOI&hl=en&ei=6kk_TZOeNImycdLyidEB&sa=X&oi=book_result&ct=result&resnum=6&ved=0CDkQ6AEwBTgK#v=onepage&q=conversion%20deadlock&f=false The dlm also does lock timeouts which could be used to approximate deadlock detection/resolution. I wrote a "toy" proof of concept for full deadlock detection once. The code still exists in dlm_controld, I'm not sure if the sufficient flags exist in the API to enable and play with it any more (that's about all it's good for.) > EDEADLOCK The lock operation is causing a deadlock and has been > cancelled. If this was a conversion then the lock is > reverted to its previously granted state. If it was a > new lock then it has not been granted. (NB Only > conversion deadlocks are currently detected)" It does note the limitation. Dave -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
