Well, this should have been introduced by recent landing of "LU-8066 obdclass : Add infrastructure for procfs to sysfs migration" master's patch, commit 4594c6656d3224eb4f8eff100a2320df53c05a8f.
Do you mean this problem is 100% reproducible on a single-node setup ?
If yes, I can try to reproduce, but if not a crash-dump from an occurrence on your side would be helpful.
Hi Bruno,
This is 100% reproducable. So, would you please reproduce it? Uploading crash dump costs too much time for me. And I think a reproduce environment is helpful for testing the patch later. 
Sure, I told you 
Humm sorry but, trying to mount/umount Client on a single-node setup does not reproduce for me...
And this even after running some activity/file-creations in between, so can you better describe/detail the exact way/config you are using to reproduce 100% on your side ?
To be complete I am using the current master version which has only the following list of patch on top of yours :
6c63418 LU-9500 lnd: Don't Page Align remote_addr with FastReg c084c62 LU-9749 llite: Reduce overhead for ll_do_fast_read 834e942 LU-7129 tests: fsx with directio 25e1cea LU-9772 utils: Enable new ZFS MMP on mkfs 9761b5c LU-9769 lnet: Fix lost lock c4ff984 LU-9019 target: migrate to 64 bit time 829a24f LU-8849 ofd: Client hanges on ladvise with large start values b2c8846 LU-6210 utils: Use C99 struct initializer for long_opt_start .......................
For this to be triggered the osp module must be loaded before the osc module. To see why look at the part of osc_setup() that calls lprocfs_obd_setup().
diff --git a/lustre/tests/test-framework.sh b/lustre/tests/test-framework.sh
index e94f941..6e38ca1 100755
--- a/lustre/tests/test-framework.sh
+++ b/lustre/tests/test-framework.sh
@@ -621,7 +621,6 @@ load_modules_local() {
load_module fid/fid
load_module lmv/lmv
load_module mdc/mdc
- load_module osc/osc
load_module lov/lov
load_module mgc/mgc
load_module obdecho/obdecho
@@ -656,6 +655,7 @@ load_modules_local() {
load_module osp/osp
fi
+ load_module osc/osc
load_module llite/lustre
[ -d /r ] && OGDB=${OGDB:-"/r/tmp"}
OGDB=${OGDB:-$TMP}
Then do llmount.sh && umount /mnt/lustre.
2.10 is not affected but 2.11 is.
This was introduced by https://review.whamcloud.com/26020 LU-8066 obdclass : Add infrastructure for procfs to sysfs migration.
James
Do you have input on this one?
Peter
I will take a look. I have a idea of what is going on.
John knows how to fix this
John L. Hammond (john.hammond@intel.com) uploaded a new patch: https://review.whamcloud.com/28668
Subject: LU-9791 osc: always do OBD lprocfs setup
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: df2a40fb38232fd7f420747ca69ff9845bd05a48
James Simmons (uja.ornl@yahoo.com) uploaded a new patch: https://review.whamcloud.com/28747
Subject: LU-9791 obd: always call lprocfs_obd_setup
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: e0009f79b0038136fa6c01a850145b4ab13912a6
Oleg Drokin (oleg.drokin@intel.com) merged in patch https://review.whamcloud.com/28747/
Subject: LU-9791 obd: always call lprocfs_obd_setup
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 9da376b7b3526c1c5bf4c5b26fc6ed692e13f9b7
Landed for 2.11
Does this affect b2_10?
No. The sysfs stuff only has landed for 2.11.
Thanks James