Comment 21 for bug 2048945

Noticed the same here when upgrading from 6.1.0-13-amd64 to 6.5.0-0.deb12.1-amd64 (both Debian kernels) earlier this month:

============================================================================
$ sar -f /var/log/sysstat/sa20231108
                CPU %user %nice %system %iowait %steal %idle
[...]
18:30:03 all 1.03 0.00 0.45 0.04 0.00 98.47
18:40:01 all 1.07 0.00 0.52 0.05 0.00 98.36
18:50:01 all 1.07 0.00 0.53 0.04 0.00 98.37
19:00:01 all 1.35 0.00 0.69 0.08 0.00 97.88
19:10:04 all 1.09 0.00 0.52 0.07 0.00 98.31
19:20:02 all 1.14 0.00 0.51 0.05 0.00 98.30
19:30:04 all 1.62 0.00 0.65 0.08 0.00 97.65
Average: all 1.06 0.00 0.50 0.06 0.00 98.38

19:32:27 LINUX RESTART (2 CPU)

19:40:03 CPU %user %nice %system %iowait %steal %idle
19:50:00 all 2.27 0.00 3.23 57.40 0.00 37.11
20:00:02 all 1.29 0.00 2.70 59.27 0.00 36.75
20:10:03 all 1.48 0.00 2.93 58.38 0.00 37.21
20:20:03 all 1.40 0.00 2.94 58.93 0.00 36.73
20:30:02 all 1.39 0.00 2.87 59.99 0.00 35.74
20:40:03 all 1.48 0.00 3.44 59.83 0.00 35.26
20:50:00 all 1.29 0.00 2.88 60.84 0.00 34.98
21:00:03 all 1.31 0.00 2.63 59.81 0.00 36.25
21:10:03 all 1.33 0.00 2.72 59.85 0.00 36.09
21:20:01 all 1.31 0.00 2.82 59.28 0.00 36.59
21:30:01 all 1.39 0.00 2.92 60.51 0.00 35.18
21:40:01 all 1.34 0.00 3.04 60.04 0.00 35.57
21:50:03 all 1.29 0.00 2.51 59.79 0.00 36.41
22:00:03 all 1.36 0.00 3.23 59.81 0.00 35.59
22:10:03 all 1.37 0.00 2.56 59.13 0.00 36.93
22:20:03 all 1.36 0.00 2.88 58.46 0.00 37.29
22:30:03 all 1.31 0.00 2.65 59.07 0.00 36.97
22:40:00 all 1.32 0.00 2.72 59.61 0.00 36.35
22:50:01 all 1.32 0.00 2.72 59.35 0.00 36.61
23:00:03 all 1.29 0.00 2.68 59.30 0.00 36.72
23:10:03 all 1.35 0.00 2.62 60.11 0.00 35.91
23:20:02 all 1.29 0.00 2.91 59.55 0.00 36.25
23:30:03 all 1.32 0.00 2.72 58.37 0.00 37.59
23:40:01 all 1.34 0.00 2.97 57.74 0.00 37.95
23:50:00 all 1.33 0.00 2.54 59.90 0.00 36.24
Average: all 1.38 0.00 2.83 59.37 0.00 36.41

$ last -n 3 reboot
reboot system boot 6.5.0-0.deb12.1- Wed Nov 8 19:32 still running
reboot system boot 6.1.0-13-amd64 Mon Oct 9 23:14 - 19:32 (29+21:17)
reboot system boot 6.1.0-13-amd64 Mon Oct 9 22:39 - 23:14 (00:35)
============================================================================

And top only shows a single [scsi_eh_2] thread using ~50% of CPU time, sometimes there's an events thread too.

    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    336 root 20 0 0.0m 0.0m 0.0m D 50.0 0.0 53,37 [scsi_eh_2]
3794126 root 20 0 0.0m 0.0m 0.0m I 25.7 0.0 0:06.27 [kworker/0:0-events]

This is a Debian/amd64 VM running on a VMware ESX host. There's a virtual CDROM drive, but nothing is attached here and I'm not using it, all:

============================================================================
$ lsblk -d --scsi
NAME HCTL TYPE VENDOR MODEL REV SERIAL TRAN
sda 0:0:0:0 disk VMware Virtual disk 2.0
sr0 2:0:0:0 rom NECVMWar VMware Virtual IDE CDROM Drive 1.00 10000000000000000001 ata

$ dmesg -t | grep -i scsi
Block layer SCSI generic (bsg) driver version 0.4 loaded (major 247)
SCSI subsystem initialized
VMware PVSCSI driver - version 1.0.7.0-k
vmw_pvscsi: using 64bit dma
vmw_pvscsi: max_id: 65
vmw_pvscsi: setting ring_pages to 32
vmw_pvscsi: enabling reqCallThreshold
vmw_pvscsi: driver-based request coalescing enabled
vmw_pvscsi: using MSI-X
scsi host0: VMware PVSCSI storage adapter rev 2, req/cmp/msg rings: 32/32/1 pages, cmd_per_lun=254
vmw_pvscsi 0000:03:00.0: VMware PVSCSI rev 2 host #0
scsi 0:0:0:0: Direct-Access VMware Virtual disk 2.0 PQ: 0 ANSI: 6
sd 0:0:0:0: [sda] Attached SCSI disk
sd 0:0:0:0: Attached scsi generic sg0 type 0
scsi host1: ata_piix
scsi host2: ata_piix
scsi 2:0:0:0: CD-ROM NECVMWar VMware IDE CDR10 1.00 PQ: 0 ANSI: 5
scsi 2:0:0:0: Attached scsi generic sg1 type 5
sr 2:0:0:0: [sr0] scsi3-mmc drive: 1x/1x writer dvd-ram cd/rw xa/form2 cdda tray
sr 2:0:0:0: Attached scsi CD-ROM sr0
============================================================================

Will that "scsi: Do no try to probe for CDL on old drives" patch land in mainline or is this still under discussion?