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From:   Jesse Hathaway <jesse@mbuki-mvuki.org>
Date:   Wed, 13 Mar 2019 11:50:07 -0500
Message-ID: <CANSNSoWiKd98Dt1N2sSjP9Af8zk1NPV-=3P4VLtFs_cSQG4RUg@mail.gmail.com>
Subject: Regression causes a hang on boot with a Comtrol PCI card
To:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        linux-kernel@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
        linux-pci@vger.kernel.org
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Sender: linux-kernel-owner@vger.kernel.org
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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