[LU-19926] ldlm should release stats after all procfs/debugfs entries

• Type: Bug
• Resolution: Unresolved
• Priority: Medium
• Severity: 3
• Assignee: WC Triage
• Reporter: Alex Zhuravlev

Description

otherwise we easily hit panic when umount races with lctl get_param:

[  411.263628] systemd[1]: mnt-lustre.mount: Deactivated successfully.
[  411.281494] LustreError: 186546:0:(lprocfs_status.c:1689:lprocfs_stats_collector()) ASSERTION( stats ) failed: 
[  411.292190] LustreError: 186546:0:(lprocfs_status.c:1689:lprocfs_stats_collector()) LBUG
[  411.292493] CPU: 4 PID: 186546 Comm: lctl Tainted: G        W  O      -------  ---  5.14.0 #24
[  411.292541] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014
[  411.292588] Call Trace:
[  411.294196]  <TASK>
[  411.294275]  dump_stack_lvl+0x57/0x7d
[  411.294331]  lbug_with_loc.cold+0x5/0x43 [libcfs]
[  411.294396]  lprocfs_stats_collector+0x120/0x130 [obdclass]
[  411.294513]  lock_count_show+0x14/0x30 [ptlrpc]
[  411.294671]  sysfs_kf_seq_show+0x92/0xd0
[  411.294708]  seq_read_iter+0x100/0x460
[  411.294745]  vfs_read+0x229/0x3b0
[  411.294782]  ksys_read+0x50/0xc0
[  411.294819]  do_syscall_64+0x38/0xe0
[  411.294856]  entry_SYSCALL_64_after_hwframe+0x4b/0x53