>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 0xfee00000: 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 0xfec00000, version 11, 24 pins acpihpet0 at acpi0: 100000000 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: <QEMU HARDDISK> 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: <QEMU, QEMU DVD-ROM, 1.0> 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: 8086:0000 Intel, UHCI root hub full speed, self powered, config 1, rev 1.00 driver: uhub0