We are running into a problem where slurmctld is segfaulting a few times a day. We had this problem with SLURM 23.11.8 and now with 23.11.10 as well, though the problem only appears on one of the several SLURM clusters we have, and all of them use one of those versions of SLURM. I was wondering if anyone has encountered a similar issue and has any thoughts on how to prevent this.

        Obviously we use "SchedulerType=sched/backfill" but strangely when I switched to sched/builtin for a while there were still slurmctld segfaults. We also set "SchedulerParameters=enable_user_top,bf_max_job_test=2000". I have tried turning those off but it did not help. I have also tried tweaking several other settings to no avail. Most of the cluster runs Rocky Linux 8.10 (including the slurmctld system) though we still have some Scientific Linux 7.9 compute nodes (we compile SLURM separately for those).

        Here is the crash-time error from journalctl:

Oct 02 06:31:20 our.host.name kernel: sched_agent[2048355]: segfault at 8 ip 00007fec755d7ea8 sp 00007fec6bffe7e8 error 4 in libslurmfull.so[7fec7555a000+1f4000]
Oct 02 06:31:20 our.host.name kernel: Code: 48 39 c1 7e 19 48 c1 f8 06 ba 01 00 00 00 48 d3 e2 48 f7 da 48 0b 54 c6 10 48 21 54 c7 10 c3 b8 00 00 00 00 eb da 48 8b 4f 08 <48> 39 4e 08 48 0f 4e 4e 08 49 89 c9 48 83 f9 3f 76 4e ba 40 00 00
Oct 02 06:31:20 our.host.name systemd[1]: Started Process Core Dump (PID 2169426/UID 0).
Oct 02 06:31:20 our.host.name systemd-coredump[2169427]: Process 2048344 (slurmctld) of user 991 dumped core.

This is followed by a list of each of the dozen or so related threads. The one which is dumping core is first and looks like this:

Stack trace of thread 2048355:
#0  0x00007fec755d7ea8 bit_and_not (libslurmfull.so)
#1  0x000000000044531f _job_alloc (slurmctld)
#2  0x000000000044576b _job_alloc_whole_node_internal (slurmctld)
#3  0x0000000000446e6d gres_ctld_job_alloc_whole_node (slurmctld)
#4  0x00007fec722e29b8 job_res_add_job (select_cons_tres.so)
#5  0x00007fec722f7c32 select_p_select_nodeinfo_set (select_cons_tres.so)
#6  0x00007fec756e7dc7 select_g_select_nodeinfo_set (libslurmfull.so)
#7  0x0000000000496eb3 select_nodes (slurmctld)
#8  0x0000000000480826 _schedule (slurmctld)
#9  0x00007fec753421ca start_thread (libpthread.so.0)
#10 0x00007fec745f78d3 __clone (libc.so.6)

       I have run slurmctld with "debug5" level logging and it appears that the error occurs right after backfill considers a large number of jobs. Slurmctld could be failing at the end of backfill or when doing something which happens just after backfill runs. Usually this is the last message before the crash:

[2024-09-25T18:39:42.076] slurmscriptd: debug:  _slurmscriptd_mainloop: finished

       If anyone has any thoughts or advice on this that would be appreciated. Thank you.

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Marcus Lauer
Systems Administrator
CETS Group, Research Support