Two regressions cause Linux to hang on boot when a Comtrol PCI card is present. If I revert the following two commits, I can boot again and the card operates without issue: 1302fcf0d03e (refs/bisect/bad) PCI: Configure *all* devices, not just hot-added ones 1c3c5eab1715 sched/core: Enable might_sleep() and smp_processor_id() checks early ; lspci -vs 82:00.0 82:00.0 Multiport serial controller: Comtrol Corporation Device 0061 Subsystem: Comtrol Corporation Device 0061 Flags: 66MHz, medium devsel, IRQ 35, NUMA node 1 Memory at c8004000 (32-bit, non-prefetchable) [size=4K] Memory at c8000000 (32-bit, non-prefetchable) [size=16K] Capabilities: [40] Hot-plug capable Capabilities: [48] Power Management version 2 Kernel driver in use: rp2 Kernel modules: rp2 Is it possible that the problem is that the card claims to support Hot-plug, but does not? I would love to help fix this issue, please let me know what other information would be helpful to provide. ; awk -f scripts/ver_linux If some fields are empty or look unusual you may have an old version. Compare to the current minimal requirements in Documentation/Changes. Linux tty01 5.0.1-amd64 #1 SMP Wed Mar 13 15:43:44 UTC 2019 x86_64 GNU/Linux GNU C 6.3.0 GNU Make 4.1 Binutils 2.28 Util-linux 2.29.2 Mount 2.29.2 Linux C Library 2.24 Dynamic linker (ldd) 2.24 Procps 3.3.12 Sh-utils 8.26 Udev 232 Modules Loaded 8021q acpi_power_meter aesni_intel aes_x86_64 ahci autofs4 bonding button coretemp crc16 crc32c_generic crc32c_intel crc32_pclmul crct10dif_pclmul cryptd crypto_simd dca dcdbas dm_mod drm drm_kms_helper ehci_hcd ehci_pci evdev ext4 fscrypto garp ghash_clmulni_intel glue_helper i2c_algo_bit igb intel_cstate intel_powerclamp intel_rapl intel_rapl_perf intel_uncore ioatdma ipmi_devintf ipmi_msghandler ipmi_si iptable_filter ip_tables irqbypass iTCO_vendor_support iTCO_wdt ixgbe jbd2 kvm kvm_intel libahci libata libcrc32c libphy llc lpc_ich mbcache mdio megaraid_sas mei mei_me mgag200 mrp mxm_wmi nf_conntrack nf_defrag_ipv4 nf_defrag_ipv6 pcc_cpufreq pcspkr rp2 sb_edac scsi_mod sd_mod sg snd snd_pcm snd_timer soundcore stp ttm usbcore wmi x86_pkg_temp_thermal xfrm_algo x_tables xt_conntrack xt_tcpudp