[LU-2597] Soft lockup messages on Sequoia in ptlrpc_check_set under ll_fsync

• Type: Bug
• Resolution: Fixed
• Priority: Blocker
• Affects Version/s: Lustre 2.4.0
• Labels: MB sequoia topsequoia
• Severity: 3
• Assignee: nasf (Inactive)
• Reporter: Prakash Surya (Inactive)

Description

This looks similar to LU-2263, but looking at the stacks and function address listings I'm not certain they are the same just yet.

When running a large IOR using our 2.3.58-3chaos tag, we saw many CPU Soft Lockup messages on the console of many clients. All of the stacks I have been able to uncover look like this:

NIP [c000000000439724] ._spin_lock+0x2c/0x44                                       
LR [8000000003a8e81c] .ptlrpc_check_set+0x43cc/0x5120 [ptlrpc]                     
Call Trace:                                                                        
[c0000003ec7bf600] [8000000003a8e75c] .ptlrpc_check_set+0x430c/0x5120 [ptlrpc] (unreliable)
[c0000003ec7bf7b0] [8000000003a8fa5c] .ptlrpc_set_wait+0x4ec/0xcb0 [ptlrpc]        
[c0000003ec7bf920] [8000000003a90974] .ptlrpc_queue_wait+0xd4/0x380 [ptlrpc]       
[c0000003ec7bf9e0] [80000000059c3564] .mdc_sync+0x104/0x340 [mdc]                  
[c0000003ec7bfa90] [800000000709bf08] .lmv_sync+0x2c8/0x820 [lmv]                  
[c0000003ec7bfb80] [80000000068232dc] .ll_fsync+0x23c/0xc50 [lustre]               
[c0000003ec7bfc80] [c000000000100420] .vfs_fsync_range+0xb0/0x104                  
[c0000003ec7bfd30] [c000000000100518] .do_fsync+0x3c/0x6c                          
[c0000003ec7bfdc0] [c000000000100588] .SyS_fsync+0x18/0x28                         
[c0000003ec7bfe30] [c000000000000580] syscall_exit+0x0/0x2c

Searching through all of the console logs for that day, I found three unique address within ptlrpc_check_set listed:

$ grep -E "LR.*ptlrpc_check_set" R* | grep 2013-01-08 | \
  sed 's/.*\(ptlrpc_check_set+[a-z0-9]\+\).*/\1/' | \
  sort | uniq
ptlrpc_check_set+0x43cc
ptlrpc_check_set+0x50c
ptlrpc_check_set+0xeec

Listing these addresses is a bit confusing to me, they aren't near any spin_lock calls as I expected. Rather, they seem to correlate to debug print statements.

ptlrpc_check_set+0x43cc

(gdb) l *ptlrpc_check_set+0x43cc
0x4e81c is in ptlrpc_check_set (/builddir/build/BUILD/lustre-2.3.58/lustre/ptlrpc/client.c:1113).

1109 static int ptlrpc_check_status(struct ptlrpc_request *req)                      
1110 {                                                                               
1111         int err;                                                                
1112         ENTRY;                                                                  
1113                                                                                 
1114         err = lustre_msg_get_status(req->rq_repmsg);                            
1115         if (lustre_msg_get_type(req->rq_repmsg) == PTL_RPC_MSG_ERR) {           
1116                 struct obd_import *imp = req->rq_import;                        
1117                 __u32 opc = lustre_msg_get_opc(req->rq_reqmsg);

ptlrpc_check_set+0x50c

(gdb) l *ptlrpc_check_set+0x50c
0x4a95c is in ptlrpc_check_set (/builddir/build/BUILD/lustre-2.3.58/lustre/ptlrpc/client.c:1774).

1771                 ptlrpc_rqphase_move(req, RQ_PHASE_COMPLETE);                    
1772                                                                                 
1773                 CDEBUG(req->rq_reqmsg != NULL ? D_RPCTRACE : 0,                 
1774                         "Completed RPC pname:cluuid:pid:xid:nid:"               
1775                         "opc %s:%s:%d:"LPU64":%s:%d\n",                         
1776                         cfs_curproc_comm(), imp->imp_obd->obd_uuid.uuid,        
1777                         lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,

Any ideas?

I'm working on getting CONFIG_DEBUG_SPINLOCK and CONFIG_LOCK_STAT enabled on the IONs. I'm hopeful that will work and will allow me to determine which spin lock the threads are contending on.

Issue Links

• is related to: LU-2263 CPU Soft Lockups due to many threads spinning on import lock on Sequoia IO nodes