On Wed, 2019-04-24 at 11:07 +0200, Martin Wilck wrote: > Since commit d7188fcd "multipathd: start daemon after udev trigger", > multipathd startup is delayed during boot until after "udev settle" > terminates. But "multipath -u" is run by udev workers for storage > devices, > and attempts to connect to the multipathd socket. This causes a start > job > for multipathd to be scheduled by systemd, but that job won't be > started > until "udev settle" finishes. This is not a problem on systems with > 129 or > less storage units, because the connect() call of "multipath -u" will > succeed anyway. But on larger systems, the listen backlog of the > systemd > socket can be exceeded, which causes connect() calls for the socket > to > block until multipathd starts up and begins calling accept(). This > creates > a deadlock situation, because "multipath -u" (called by udev workers) > blocks, and thus "udev settle" doesn't finish, delaying multipathd > startup. This situation then persists until either the workers or > "udev > settle" time out. In the former case, path devices might be > misclassified > as non-multipath devices by "multipath -u". > > Fix this by using a non-blocking socket fd for connect() and > interpret the > errno appropriately. > > This patch reverts most of the changes from commit 8cdf6661 > "multipath: > check on multipathd without starting it". Instead, "multipath -u" > does > access the socket and start multipath again (which is what we want > IMO), > but it is now able to detect and handle the "full backlog" situation. > > Signed-off-by: Martin Wilck <mwilck@xxxxxxxx> > > V2: > > Use same error reporting convention in __mpath_connect() as in > mpath_connect() (Hannes Reinecke). We can't easily change the latter, > because it's part of the "public" libmpathcmd API. FTR, our customer reported that this patch fixed his problem. @Ben, I'd be grateful if you could try it (or have the user try it) in your problem case as well. -- Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
