(I can't get References: right on this mail due to the original aging out of my mailbox: archive URL, https://www.spinics.net/lists/linux-nfs/msg81430.html). I now have a little lockdep info from this hang (and reports from at least two others that they've seen similar-looking hangs dating back to 4.19, though much harder to reproduce, taking many hours rather than five minutes: in one case they report not using NFS in production any more because of this). Unfortunately the lockdep info isn't much use: Feb 13 14:13:12 silk warning: : [ 888.834464] Showing all locks held in the system: Feb 13 14:13:12 silk warning: : [ 888.834501] 1 lock held by dmesg/1152: Feb 13 14:13:12 silk warning: : [ 888.834508] #0: ffff980c3b7200d0 (&user->lock){+.+.}-{3:3}, at: devkmsg_read+0x49/0x2d1 Feb 13 14:13:12 silk warning: : [ 888.834540] 2 locks held by tee/1322: Feb 13 14:13:12 silk warning: : [ 888.834546] #0: ffff980c0809a430 (sb_writers#12){.+.+}-{0:0}, at: ksys_write+0x6a/0xdc Feb 13 14:13:12 silk warning: : [ 888.834573] #1: ffff980c3ca7b5e8 (&sb->s_type->i_mutex_key#16){++++}-{3:3}, at: nfs_start_io_write+0x1a/0x45 Feb 13 14:13:12 silk warning: : [ 888.834632] 1 lock held by 192.168.16.8-ma/2302: Feb 13 14:13:12 silk warning: : [ 888.834638] #0: ffff980c0fe6b700 (&acct->lock#2){+.+.}-{3:3}, at: acct_process+0x102/0x2bc The first of those is my ongoing dmesg -w. The last is process accounting. The middle one is an ongoing, always-active Xsession-errors tee over the same NFSv4 connection, which says nothing more than that writes to this NFS server from this client have hung, which we already know. There are no signs of locks held by the Steam client which has hung in the middle of installation. So whateverthehell this is, it's not blocked on a lock. The NFS client is hanging all on its own. (I have no idea how clients can block in the middle of writing if a lock is *not* involved somehow, but that is what it looks like from the lockdep output.) Does anyone know how I might start debugging this sod?
