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    rcu_sched stall OR kernel panic on PowerEdge R640

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    • Q
      Quazz Moderator
      last edited by

      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.

      george1421G 1 Reply Last reply Reply Quote 0
      • george1421G
        george1421 Moderator @Quazz
        last edited by

        @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.

        Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

        Q 1 Reply Last reply Reply Quote 0
        • Q
          Quazz Moderator @george1421
          last edited by

          @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?

          george1421G 1 Reply Last reply Reply Quote 1
          • george1421G
            george1421 Moderator @Quazz
            last edited by

            @Quazz That is surely something we can test.

            Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

            1 Reply Last reply Reply Quote 0
            • D
              djgalloway
              last edited by

              @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.

              george1421G 1 Reply Last reply Reply Quote 0
              • george1421G
                george1421 Moderator @djgalloway
                last edited by

                @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.

                Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

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                • D
                  djgalloway
                  last edited by

                  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
                  
                  george1421G 1 Reply Last reply Reply Quote 0
                  • george1421G
                    george1421 Moderator @djgalloway
                    last edited by george1421

                    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

                    Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

                    JunkhackerJ 1 Reply Last reply Reply Quote 0
                    • JunkhackerJ
                      Junkhacker Developer @george1421
                      last edited by

                      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.

                      signature:
                      Junkhacker
                      We are here to help you. If you are unresponsive to our questions, don't expect us to be responsive to yours.

                      george1421G 1 Reply Last reply Reply Quote 0
                      • george1421G
                        george1421 Moderator @Junkhacker
                        last edited by george1421

                        @Junkhacker @Sebastian-Roth

                        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.

                        Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

                        george1421G 1 Reply Last reply Reply Quote 1
                        • george1421G
                          george1421 Moderator @george1421
                          last edited by Sebastian Roth

                          @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 Nodes

                          We 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.

                          Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

                          1 Reply Last reply Reply Quote 4
                          • S
                            Sebastian Roth Moderator
                            last edited by

                            @george1421 @Quazz @djgalloway Great work!!! Thanks to you all. I will add this in the next days!

                            Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

                            Please support FOG if you like it: https://wiki.fogproject.org/wiki/index.php/Support_FOG

                            1 Reply Last reply Reply Quote 1
                            • S
                              Sebastian Roth Moderator
                              last edited by

                              @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 adding CONFIG_MAXSMP (Enable Maximum number of SMP Processors and NUMA Nodes). Found this topic: https://www.xenomai.org/pipermail/xenomai/2018-July/039297.html

                              Though 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?

                              Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

                              Please support FOG if you like it: https://wiki.fogproject.org/wiki/index.php/Support_FOG

                              george1421G Q 2 Replies Last reply Reply Quote 0
                              • george1421G
                                george1421 Moderator @Sebastian Roth
                                last edited by

                                @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.

                                Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

                                1 Reply Last reply Reply Quote 0
                                • S
                                  Sebastian Roth Moderator
                                  last edited by

                                  @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.

                                  Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

                                  Please support FOG if you like it: https://wiki.fogproject.org/wiki/index.php/Support_FOG

                                  1 Reply Last reply Reply Quote 2
                                  • Q
                                    Quazz Moderator @Sebastian Roth
                                    last edited by

                                    @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.

                                    1 Reply Last reply Reply Quote 0
                                    • S
                                      Sebastian Roth Moderator
                                      last edited by

                                      @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?

                                      Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

                                      Please support FOG if you like it: https://wiki.fogproject.org/wiki/index.php/Support_FOG

                                      Q 1 Reply Last reply Reply Quote 0
                                      • Q
                                        Quazz Moderator @Sebastian Roth
                                        last edited by Quazz

                                        @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 enables CPUMASK_OFFSTACK
                                        , which it requires to function correctly I believe (or any high CONFIG_NR_CPUS would at least)

                                        1 Reply Last reply Reply Quote 0
                                        • S
                                          Sebastian Roth Moderator
                                          last edited by

                                          @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?

                                          Web GUI issue? Please check apache error (debian/ubuntu: /var/log/apache2/error.log, centos/fedora/rhel: /var/log/httpd/error_log) and php-fpm log (/var/log/php*-fpm.log)

                                          Please support FOG if you like it: https://wiki.fogproject.org/wiki/index.php/Support_FOG

                                          george1421G 1 Reply Last reply Reply Quote 0
                                          • george1421G
                                            george1421 Moderator @Sebastian Roth
                                            last edited by

                                            @Sebastian-Roth said in rcu_sched stall OR kernel panic on PowerEdge R640:

                                            Did you get to test this kernel on your fleet of Dell hardware to see if it might cause any other harm?

                                            TBH, no I did not test it. I haven’t found any other system that the max-cpu value fixed either. We had one dual core with the rcu_sched stall, but that was fixed with the current kernel and changing the acpi clock source that Quazz posted. I think the max-cpu will only impact CPUs with more than 8 cores.

                                            Please help us build the FOG community with everyone involved. It's not just about coding - way more we need people to test things, update documentation and most importantly work on uniting the community of people enjoying and working on FOG!

                                            1 Reply Last reply Reply Quote 0
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