On Wed, May 19 2010 at 10:39am -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > > On Wed, May 19, 2010 at 1:57 AM, Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx> wrote: > > > Hi Mike, > > > > > > dm_table_setup_md_queue() may allocate memory with blocking mode. > > > Blocking allocation inside exclusive _hash_lock can cause deadlock; > > > e.g. when it has to wait for other dm devices to resume to free some > > > memory. <snip> > We discussed this and I understand the scope of the problem now. > > Just reiterating what you covered when you first pointed this issue out: > > It could be that a table load gets blocked (waiting on a memory > allocation). The table load can take as long as it needs. But we can't > have it block holding the exclusive _hash_lock while blocking. Having > _hash_lock prevents further DM ioctls. The table load's allocation may > be blocking waiting for writeback to a DM device that will be resumed by > another thread. > > Thanks again for pointing this out; I'll work to arrive at an > alternative locking scheme. Likely introduce a lock local to the > multiple_device (effectively the 'queue_lock' I had before). But s/multiple_device/mapped_device/ Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
