>Synopsis: If network drops while running top over SSH, runaway process
>Category: minor, poor handling of failure mode
>Environment:
System : OpenBSD 6.7
Details : OpenBSD 6.7 (GENERIC) #5: Wed Oct 28 00:25:20 MDT 2020
t...@syspatch-67-amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC
Architecture: OpenBSD.amd64
Machine : amd64
>Description:
If I SSH into any of various amd64 OpenBSD servers, virtual or
physical,
if m running a monitoring process like top, or multitail -f, on a remote
machine
over SSH and the network drops or client machine disconnects, the server
process
consumes nearly 100% of CPU and does not stop itself. I can log back in and
kill the process, but until I do I have a CPU being consumed. This affects
performance, possibly costing money on a virtual server. This behavior is
years old.
>How-To-Repeat:
ssh to a server, run top, and verify that top isnt all that
abusive.
Pull out the ethernet cable or disconnect your wifi on the client machine.
Kill your SSH session or terminal locally.
Reconnect your network and log back in to your server.
Run top again to check for the old abusive process.
>Fix:
Im guessing its ncurses somehow thats making this problem possible.
I have no solution, but the workaround is to log back in and kill any
runaway processes after an ungraceful network disconnect
dmesg:
OpenBSD 6.7 (GENERIC) #5: Wed Oct 28 00:25:20 MDT 2020
t...@syspatch-67-amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC
real mem = 520085504 (495MB)
avail mem = 491847680 (469MB)
mpath0 at root
scsibus0 at mpath0: 256 targets
mainbus0 at root
bios0 at mainbus0: SMBIOS rev. 2.4 @ 0xf13c0 (10 entries)
bios0: vendor Bochs version "Bochs" date 01/01/2011
bios0: Bochs Bochs
acpi0 at bios0: ACPI 1.0
acpi0: sleep states S3 S4 S5
acpi0: tables DSDT FACP SSDT APIC HPET
acpi0: wakeup devices
acpitimer0 at acpi0: 3579545 Hz, 24 bits
acpimadt0 at acpi0 addr 0xfee0: PC-AT compat
cpu0 at mainbus0: apid 0 (boot processor)
cpu0: QEMU Virtual CPU version 1.0, 2693.86 MHz, 06-02-03
cpu0:
FPU,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,MMX,FXSR,SSE,SSE2,SSE3,VMX,CX16,POPCNT,HV,NXE,LONG,LAHF,MELTDOWN
cpu0: 64KB 64b/line 2-way I-cache, 64KB 64b/line 2-way D-cache, 512KB 64b/line
16-way L2 cache
cpu0: ITLB 255 4KB entries direct-mapped, 255 4MB entries direct-mapped
cpu0: DTLB 255 4KB entries direct-mapped, 255 4MB entries direct-mapped
cpu0: smt 0, core 0, package 0
mtrr: Pentium Pro MTRR support, 8 var ranges, 88 fixed ranges
cpu0: apic clock running at 999MHz
ioapic0 at mainbus0: apid 0 pa 0xfec0, version 11, 24 pins
acpihpet0 at acpi0: 1 Hz
acpiprt0 at acpi0: bus 0 (PCI0)
acpicpu0 at acpi0: C1(@1 halt!)
"ACPI0006" at acpi0 not configured
acpipci0 at acpi0 PCI0: _OSC failed
acpicmos0 at acpi0
"ACPI0007" at acpi0 not configured
pvbus0 at mainbus0: KVM
pvclock0 at pvbus0
pci0 at mainbus0 bus 0
pchb0 at pci0 dev 0 function 0 "Intel 82441FX" rev 0x02
pcib0 at pci0 dev 1 function 0 "Intel 82371SB ISA" rev 0x00
pciide0 at pci0 dev 1 function 1 "Intel 82371SB IDE" rev 0x00: DMA, channel 0
wired to compatibility, channel 1 wired to compatibility
wd0 at pciide0 channel 0 drive 0:
wd0: 16-sector PIO, LBA48, 20480MB, 41943040 sectors
atapiscsi0 at pciide0 channel 0 drive 1
scsibus1 at atapiscsi0: 2 targets
cd0 at scsibus1 targ 0 lun 0: removable
wd0(pciide0:0:0): using PIO mode 4, DMA mode 2
cd0(pciide0:0:1): using PIO mode 4, DMA mode 2
pciide0: channel 1 disabled (no drives)
uhci0 at pci0 dev 1 function 2 "Intel 82371SB USB" rev 0x01: apic 0 int 11
piixpm0 at pci0 dev 1 function 3 "Intel 82371AB Power" rev 0x03: apic 0 int 9
iic0 at piixpm0
vga1 at pci0 dev 2 function 0 "Cirrus Logic CL-GD5446" rev 0x00
wsdisplay0 at vga1 mux 1: console (80x25, vt100 emulation)
wsdisplay0: screen 1-5 added (80x25, vt100 emulation)
em0 at pci0 dev 3 function 0 "Intel 82540EM" rev 0x03: apic 0 int 11, address
52:54:00:27:27:51
virtio0 at pci0 dev 4 function 0 "Qumranet Virtio Memory Balloon" rev 0x00
viomb0 at virtio0
virtio0: apic 0 int 11
isa0 at pcib0
isadma0 at isa0
fdc0 at isa0 port 0x3f0/6 irq 6 drq 2
com0 at isa0 port 0x3f8/8 irq 4: ns16550a, 16 byte fifo
pckbc0 at isa0 port 0x60/5 irq 1 irq 12
pckbd0 at pckbc0 (kbd slot)
wskbd0 at pckbd0: console keyboard, using wsdisplay0
pms0 at pckbc0 (aux slot)
wsmouse0 at pms0 mux 0
pcppi0 at isa0 port 0x61
spkr0 at pcppi0
usb0 at uhci0: USB revision 1.0
uhub0 at usb0 configuration 1 interface 0 "Intel UHCI root hub" rev 1.00/1.00
addr 1
vmm0 at mainbus0: VMX/EPT (using slow L1TF mitigation)
vscsi0 at root
scsibus2 at vscsi0: 256 targets
softraid0 at root
scsibus3 at softraid0: 256 targets
root on wd0a (d5f96b00d42d0034.a) swap on wd0b dump on wd0b
fd0 at fdc0 drive 1: density unknown
usbdevs:
Controller /dev/usb0:
addr 01: 8086: Intel, UHCI root hub
full speed, self
