rcu_sched stall OR kernel panic on PowerEdge R640
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Kernel command line: loglevel=7 initrd=init.xz root=/dev/ram0 rw ramdisk_size=127000 web=http://10.8.128.2/fog/ consoleblank=0 rootfstype=ext4 console=tty0 console=ttyS1,115200 nosmp mac=e4:43:4b:7d:a9:ba ftp=10.8.128.2 storage=10.8.128.2:/opt/fog/images/dev/ storageip=1p Misrouted IRQ fixup and polling support enabled This may significantly impact system performance Dentry cache hash table entries: 8388608 (order: 14, 67108864 bytes) Inode-cache hash table entries: 4194304 (order: 13, 33554432 bytes) Memory: 97288196K/99055148K available (16392K kernel code, 992K rwdata, 4548K rodata, 1056K init, 2416K bss, 1766952K reserved, 0K cma-reserved) SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1 Kernel/User page tables isolation: enabled rcu: Hierarchical RCU implementation. rcu: RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=1. rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1 NR_IRQS: 4352, nr_irqs: 32, preallocated irqs: 16 Console: colour VGA+ 80x25 console [tty0] enabled console [ttyS1] enabled ACPI: Core revision 20180810 ACPI: setting ELCR to 0200 (from 0820) clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635855245 ns APIC: SMP mode deactivated APIC: Switch to symmetric I/O mode setup in no SMP routine BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 PGD 0 P4D 0 Oops: 0002 [#1] SMP PTI CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.64 #1 Hardware name: Dell Inc. PowerEdge R640/08HT8T, BIOS 2.2.11 06/13/2019 RIP: 0010:0xffffffff8102d1e6 Code: c2 48 8b 14 d5 00 53 62 82 4a 8b 1c 22 48 85 db 74 d7 3b 2b 75 d3 eb 14 48 8b 1d 25 60 d8 01 48 c7 05 1a 60 d8 01 00 00 00 00 <89> 2b 65 48 89 1d 98 7c fe 7e 65 8b 05 39 1f fe 7e 89 c0 f0 48 0f RSP: 0000:ffffffff82803e98 EFLAGS: 00010202 RAX: 0000000000000008 RBX: 0000000000000000 RCX: 0000000000000040 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff828f36f0 RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff81408bd7 R10: 0000000000000000 R11: 000000000000005c R12: 0000000000014e88 R13: ffffffff82d460a0 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8897e1000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000002812001 CR4: 00000000000606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: 0xffffffff81028ad4 0xffffffff82cc1652 0xffffffff82cb691a 0xffffffff82cafd33 0xffffffff810000d4 Modules linked in: CR2: 0000000000000000 ---[ end trace f19259880c7c4bbb ]--- RIP: 0010:0xffffffff8102d1e6 Code: c2 48 8b 14 d5 00 53 62 82 4a 8b 1c 22 48 85 db 74 d7 3b 2b 75 d3 eb 14 48 8b 1d 25 60 d8 01 48 c7 05 1a 60 d8 01 00 00 00 00 <89> 2b 65 48 89 1d 98 7c fe 7e 65 8b 05 39 1f fe 7e 89 c0 f0 48 0f RSP: 0000:ffffffff82803e98 EFLAGS: 00010202 RAX: 0000000000000008 RBX: 0000000000000000 RCX: 0000000000000040 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff828f36f0 RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff81408bd7 R10: 0000000000000000 R11: 000000000000005c R12: 0000000000014e88 R13: ffffffff82d460a0 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8897e1000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000002812001 CR4: 00000000000606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Kernel panic - not syncing: Attempted to kill the idle task! ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---
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We may have to enable kernel config option
CONFIG_INTEL_IDLE
to improve support for certain Intel CPUs.We may also want to to bump up
CONFIG_NR_CPUS
from the default of 8 to 512 (common value on modern kernels) at least on the x64 config, though this one shouldn’t cause a crash.That said, I am doubtful that would resolve this issue.
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@Quazz said in rcu_sched stall OR kernel panic on PowerEdge R640:
We may also want to to bump up CONFIG_NR_CPUS from the default of 8 to 512
I’ve seen this setting in the kernel. I considered requesting the value set to 0 so it uses all available processors, but then I had to think this is for imaging and not a general purposes so having 28 cores available for imaging does really help because at most 4 threads (guess) would be used during imaging since most of the process is single threaded.
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@george1421 Yes, I think that’s why it was left at 8 in the config, though perhaps some CPUs don’t handle a majority of their cores being ignored very well?
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@Quazz That is surely something we can test.
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@george1421 are you working on building a kernel with @Quazz’s suggestions or should I? I don’t have experience building a kernel from scratch but I can probably figure it out.
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@djgalloway Sorry I got side tracked this AM. I almost had it built. Give me a few and I’ll send you a link to the kernel via IM chat.
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Here’s the latest output using the debug kernel:
console [ttyS1] enabled bootconsole [earlyvga0] disabled ACPI: Core revision 20180810 clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635855245 ns APIC: Switch to symmetric I/O mode setup x2apic: IRQ remapping doesn't support X2APIC mode x2apic disabled Switched APIC routing to flat. ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1 clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1fb633008a4, max_idle_ns: 440795292230 ns Calibrating delay loop (skipped), value calculated using timer frequency.. 4400.00 BogoMIPS (lpj=2200000) pid_max: default: 32768 minimum: 301 Mount-cache hash table entries: 131072 (order: 8, 1048576 bytes) Mountpoint-cache hash table entries: 131072 (order: 8, 1048576 bytes) ENERGY_PERF_BIAS: Set to 'normal', was 'performance' ENERGY_PERF_BIAS: View and update with x86_energy_perf_policy(8) process: using mwait in idle threads Last level iTLB entries: 4KB 64, 2MB 8, 4MB 8 Last level dTLB entries: 4KB 64, 2MB 0, 4MB 0, 1GB 4 Spectre V1 : Mitigation: usercopy/swapgs barriers and __user pointer sanitization Spectre V2 : Mitigation: Full generic retpoline Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch Spectre V2 : Enabling Restricted Speculation for firmware calls Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction Barrier Spectre V2 : User space: Mitigation: STIBP via seccomp and prctl Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled via prctl and seccomp MDS: Mitigation: Clear CPU buffers Freeing SMP alternatives memory: 52K smpboot: CPU0: Intel(R) Xeon(R) Silver 4114 CPU @ 2.20GHz (family: 0x6, model: 0x55, stepping: 0x4) Performance Events: PEBS fmt3+, Skylake events, 32-deep LBR, full-width counters, Intel PMU driver. ... version: 4 ... bit width: 48 ... generic registers: 4 ... value mask: 0000ffffffffffff ... max period: 00007fffffffffff ... fixed-purpose events: 3 ... event mask: 000000070000000f rcu: Hierarchical SRCU implementation. smp: Bringing up secondary CPUs ... x86: Booting SMP configuration: .... node #0, CPUs: #1 #2 #3 #4 #5 #6 #7 smp: Brought up 1 node, 8 CPUs smpboot: Max logical packages: 10 smpboot: Total of 8 processors activated (35220.85 BogoMIPS) devtmpfs: initialized clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275000 ns futex hash table entries: 2048 (order: 5, 131072 bytes) xor: automatically using best checksumming function avx pinctrl core: initialized pinctrl subsystem rcu: INFO: rcu_sched self-detected stall on CPU rcu: 0-....: (20999 ticks this GP) idle=04a/1/0x4000000000000002 softirq=10/10 fqs=5241 rcu: (t=21000 jiffies g=-1175 q=19) NMI backtrace for cpu 0 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.65 #12 Hardware name: Dell Inc. PowerEdge R640/08HT8T, BIOS 2.2.11 06/13/2019 Call Trace: <IRQ> 0xffffffff81d6ecad 0xffffffff81d7222f ? 0xffffffff8102b073 0xffffffff81d7228a 0xffffffff8107ce90 0xffffffff8107c41d 0xffffffff810806b4 0xffffffff8108a34e 0xffffffff81e017d5 0xffffffff81e013af </IRQ> RIP: 0010:0xffffffff8108fa1d Code: 36 48 89 de 89 c7 e8 ca ef cd 00 3b 05 c0 13 86 01 73 24 48 63 f0 49 8b 16 48 03 14 f5 30 83 61 82 8b 72 18 40 80 e6 01 74 04 <f3> 90 eb f3 eb d1 0f 0b e9 72 fe ff ff 48 83 c4 10 5b 5d 41 5c 41 RSP: 0000:ffffc9000007fae0 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000001 RBX: ffff8897e101fac8 RCX: 0000000000000001 RDX: ffff8897e10621c0 RSI: 0000000000000001 RDI: ffff8897e101fac8 RBP: 000000000001fa80 R08: 0000000000000000 R09: 00000000016daed4 R10: ffffc9000007fb58 R11: 000fffffffe00000 R12: 0000000000000001 R13: 0000000000000008 R14: ffff8897e101fac0 R15: 0000000000000000 ? 0xffffffff81039a
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Just for grins I had the OP boot a 486 kernel I built for another poster for a specific dedicated machine to image with FOG. That kernel gave a bit more details than the full system kernel .
Checking if this processor honours the WP bit even in supervisor mode...Ok. SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=8, Nodes=1 rcu: Hierarchical RCU implementation. NR_IRQS: 2304, nr_irqs: 1848, preallocated irqs: 16 Console: colour VGA+ 80x25 console [tty0] enabled console [ttyS1] enabled ACPI: Core revision 20180810 clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635855245 ns APIC: Switch to symmetric I/O mode setup Enabling APIC mode: Flat. Using 9 I/O APICs ------------[ cut here ]------------ Kernel BUG at 0xc1028128 [verbose debug info unavailable] invalid opcode: 0000 [#1] SMP CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.65 #2 Hardware name: Dell Inc. PowerEdge R640/08HT8T, BIOS 2.2.11 06/13/2019 EIP: 0xc1028128
It looks like the kernel is crashing at enabling apic mode or with the apic IO. The clock source hpet also is memorable for some reason.
So the kernel is crashing at the same point. For reference the 486 compatible kernel is also “Linux version 4.19.65”
acpi=ht
acpi=oldboot
acpi_osi=Linux
noapic
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i was googling the problem a bit and i was curious, will it boot if you remove the raid card?
just trying to understand the source of the panic. -
I was able to get the OP going by doing this and that.
We are not sure if it was this or that that got the kernel to boot. What I did was unlocked the max CPUs (that was capped at in the kernel and I also enabled almost all of the ACPI modules in the kernel. We also tried the
acpi_osi=Linux
kernel parameter.We ruled out the
acpi_osi=Linux
kernel parameter fixing the issue so it must be something I enabled in the kernel. Tomorrow AM I’m going to reset the kernel environment and only unlock the max CPUs. The OP is going to test that new kernel to see if it was unlocking the max cpu or it was the acpi modules I enabled.Either way I’ll report where we ended up and which kernel change fixed the issue. I have also seen other recent CPU stalls like this that was fixed by setting
acpi=off
so we may need to move what ever fixed the issue into the main kernel build because new hardware/cpus may require it. -
@developers Here’s the final update on this issue.
I reset my kernel build environment and then created 2 new kernel builds. The first was to remove the imposed CPU limit on the linux kernel this kernel was called bzImageMaxCPU. I reset the kernel build environment and then went through the ACPI settings turning on what I turned on in the debug kernel. This kernel was called bzImageACPI.
The OP tested both and the bzImageMaxCPU was the only kernel that booted on those Dell servers. So in the end @Quazz was right about the CPU not liking some of its cores disabled.
So I would recommend that we add the following settings to the official kernel build
CONFIG_INTEL_IDLE
and
Processor type and features —>
Enable Maximum number of SMP Processors and NUMA NodesWe have seen a recent uptick in reports of rcu_sched stalls with kernel panics Maybe we are running into this issue more often as the core counts go up on these processors.
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@george1421 @Quazz @djgalloway Great work!!! Thanks to you all. I will add this in the next days!
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@george1421 @Quazz I found a bit of time to look into this. Adding
CONFIG_INTEL_IDLE
should be just fine I think. But I am not exactly sure about addingCONFIG_MAXSMP
(Enable Maximum number of SMP Processors and NUMA Nodes). Found this topic: https://www.xenomai.org/pipermail/xenomai/2018-July/039297.htmlThough I am not convinced this will actually cause trouble it’s still a bit risky. @Testers @Moderators. Would you be able to run a test kernel on several different client machines so we get a feeling of this being troublesome or not?
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@Sebastian-Roth I can test it here, but I don’t have a system that is causing this rcu_sched issue. But I can surely test it against our current fleet of Dell systems to see if it does any harm.
We can also hold this “test” kernel in reserve in case this issue comes up again if you don’t want to release it as general availability. What I would not like to see is having a special kernel for this, and a different special kernel for that.
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@george1421 said in rcu_sched stall OR kernel panic on PowerEdge R640:
We can also hold this “test” kernel in reserve in case this issue comes up again if you don’t want to release it as general availability.
Don’t get me wrong on this. I am more than happy to make this the default kernel for everyone. It comes at low cost. But I’d like to see this tested on several different machines (PC as well as notebooks and even servers if possible) before we make it the new default kernel.
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@Sebastian-Roth As far as I understand it, Xenomai implements a patch to the kernel that does all kinds of stuff, potentially it’s not compatible with their patches, but as far as I know
CONFIG_MAXSMP
is in fact enabled by default on Kernel 4.4+ or so on all major distributions without issues.That said, I don’t mind testing it.
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@Quazz said in rcu_sched stall OR kernel panic on PowerEdge R640:
as far as I know CONFIG_MAXSMP is in fact enabled by default on Kernel 4.4+ or so on all major distributions without issues
That’s valuable information! Any reference for this?
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@Sebastian-Roth Hmm, I may have been misremembering, though their
CONFIG_NR_CPUS
is going to be much higher than 8 at the very least. (at least 512 afaik)The only difference I can find is that
CONFIG_MAXSMP
enablesCPUMASK_OFFSTACK
, which it requires to function correctly I believe (or any highCONFIG_NR_CPUS
would at least) -
@Quazz @george1421 Ok, back from travels… what shall we do with this pending topic. I do understand that adding
CONFIG_MAXSMP
does fix the rcu_sched stall issue on PowerEdge R640. But do we know if this fixes rcu_sched stalls on other platforms as well? Would we get at least two more people to test this before we add it to the official kernel?@george1421 Did you get to test this kernel on your fleet of Dell hardware to see if it might cause any other harm?