Comment # 5 on bug 907595 from David Sterba

All the processes are in Z state so they're not blocking. It's up to zypper to
recognize this state and finish. It's in the S (sleeping) state and according
to the log waiting for data:

zypper          S ffff88017fc53a40     0 14996  14995 0x00000080
 ffff8801657e3d78 0000000000000082 ffff8801654b2610 0000000000013a40
 ffff8801657e3fd8 0000000000013a40 ffff880179878450 ffff8801654b2610
 0000000000000246 ffff88003fc45640 0000000000000000 0000000000001000
Call Trace:
 [<ffffffff811d458f>] pipe_wait+0x5f/0xa0
 [<ffffffff811d4c1b>] pipe_read+0x18b/0x2f0
 [<ffffffff811cbf01>] new_sync_read+0x71/0xa0
 [<ffffffff811cc6b3>] vfs_read+0x93/0x170
 [<ffffffff811cd1a2>] SyS_read+0x42/0xb0
 [<ffffffff8165ef2d>] system_call_fastpath+0x16/0x1b
 [<00007f601a75c57d>] 0x7f601a75c57d

IOW looks like a zypper bug.