Messages in this thread | | | From | Sargun Dhillon <> | Date | Wed, 26 Dec 2018 14:31:30 -0500 | Subject | CPUs blocking in update_blocked_averages -- 4.19.12 |
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We're seeing an issue introduced in 4.18, and that still persists in 4.19.12 (we upgraded from 4.9), where update_blocked_averages is blocking. We're running a workload where a majority of our workloads are confined by cgroups. This exhibits itself due to a softlockup on a CPU which is waiting on a lock that's held by update_blocked_averages. I don't have access to any bare metal hardware at the moment, and these are all systems running under KVM. This kernel has CONFIG_FAIR_GROUP_SCHED on.
The Softlocked CPU: crash> bt PID: 29314 TASK: ffff99b5f0671f00 CPU: 0 COMMAND: "ag" #0 [ffff99b67b203d58] machine_kexec at ffffffff91a602f3 #1 [ffff99b67b203db0] __crash_kexec at ffffffff91b49011 #2 [ffff99b67b203e70] panic at ffffffff91a896d1 #3 [ffff99b67b203ef8] watchdog_timer_fn at ffffffff91b816af #4 [ffff99b67b203f28] __hrtimer_run_queues at ffffffff91b26359 #5 [ffff99b67b203f88] hrtimer_interrupt at ffffffff91b26de2 #6 [ffff99b67b203fd8] smp_apic_timer_interrupt at ffffffff92402b06 #7 [ffff99b67b203ff0] apic_timer_interrupt at ffffffff92401a9f --- <IRQ stack> --- #8 [ffffa49fa1acbc08] apic_timer_interrupt at ffffffff92401a9f [exception RIP: smp_call_function_many+543] RIP: ffffffff91b3e84f RSP: ffffa49fa1acbcb0 RFLAGS: 00000202 RAX: 0000000000000010 RBX: ffff99b67b224fc0 RCX: ffff99b67b6286a0 RDX: 0000000000000001 RSI: 0000000000000200 RDI: ffff99b67b224fc8 RBP: ffff99b67b224fc8 R8: 0000000000000001 R9: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000025080 R13: ffffa49fa1acbd00 R14: 0000000000000001 R15: 0000000000000200 ORIG_RAX: ffffffffffffff13 CS: 0010 SS: 0018 #9 [ffffa49fa1acbcf8] flush_tlb_mm_range at ffffffff91a7853c #10 [ffffa49fa1acbd90] free_pgtables at ffffffff91c4ac3b #11 [ffffa49fa1acbdc8] unmap_region at ffffffff91c54439 #12 [ffffa49fa1acbe90] do_munmap at ffffffff91c56355 #13 [ffffa49fa1acbee0] vm_munmap at ffffffff91c56587 #14 [ffffa49fa1acbf20] __x64_sys_munmap at ffffffff91c565e2 #15 [ffffa49fa1acbf38] do_syscall_64 at ffffffff91a04590 #16 [ffffa49fa1acbf50] entry_SYSCALL_64_after_hwframe at ffffffff9240008d RIP: 00007f43e94de747 RSP: 00007f43e91d7e28 RFLAGS: 00000213 RAX: ffffffffffffffda RBX: 00000000011a6f30 RCX: 00007f43e94de747 RDX: 0000000000000001 RSI: 0000000000000ade RDI: 00007f43ea47d000 RBP: 0000000000000005 R8: 00007f43e00008c0 R9: 00007f43e91d7d00 R10: 00000000011a53b0 R11: 0000000000000213 R12: 00007f43ea47d000 R13: 0000000000000ade R14: 00007f43e91d89c0 R15: 0000000000000060 ORIG_RAX: 000000000000000b CS: 0033 SS: 002b
This is waiting on CPU 16: crash> bt PID: 29299 TASK: ffff99b5dffd1f00 CPU: 16 COMMAND: "ag" #0 [fffffe00002c8e38] crash_nmi_callback at ffffffff91a54202 #1 [fffffe00002c8e50] nmi_handle at ffffffff91a32ee2 #2 [fffffe00002c8ea0] default_do_nmi at ffffffff91a333ea #3 [fffffe00002c8ec0] do_nmi at ffffffff91a33553 #4 [fffffe00002c8ef0] end_repeat_nmi at ffffffff924014e8 [exception RIP: native_queued_spin_lock_slowpath+33] RIP: ffffffff91af2dc1 RSP: ffffa49fa1a93948 RFLAGS: 00000002 RAX: 0000000000000001 RBX: ffff99b67b763f40 RCX: 000000004f19a57a RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffff99b67b763f40 RBP: 0000000000000082 R8: 0000000000000001 R9: 0000000000000000 R10: ffffa49fa1a938f8 R11: ffffffff91aca4a7 R12: 0000000000000015 R13: ffff99b67b764940 R14: ffffa49fa1a93a60 R15: 0000000000000015 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0000 --- <NMI exception stack> --- #5 [ffffa49fa1a93948] native_queued_spin_lock_slowpath at ffffffff91af2dc1 #6 [ffffa49fa1a93948] do_raw_spin_lock at ffffffff91af48dd #7 [ffffa49fa1a93958] _raw_spin_lock_irqsave at ffffffff923c1154 #8 [ffffa49fa1a93978] update_blocked_averages at ffffffff91aca4a7 #9 [ffffa49fa1a93a10] update_nohz_stats at ffffffff91acaa3d #10 [ffffa49fa1a93a20] find_busiest_group at ffffffff91ad2137 #11 [ffffa49fa1a93bb8] load_balance at ffffffff91ad2be0 #12 [ffffa49fa1a93cf0] pick_next_task_fair at ffffffff91ad41e6 #13 [ffffa49fa1a93da0] mark_held_locks at ffffffff91aeebe4 #14 [ffffa49fa1a93de8] schedule at ffffffff923b9ec2 #15 [ffffa49fa1a93df8] rwsem_down_read_failed at ffffffff923be859 #16 [ffffa49fa1a93e80] call_rwsem_down_read_failed at ffffffff923ae944 #17 [ffffa49fa1a93ec8] down_read at ffffffff923bdf0b #18 [ffffa49fa1a93ee0] __do_page_fault at ffffffff91a71083 #19 [ffffa49fa1a93f50] async_page_fault at ffffffff924010ee RIP: 00007f43e945f786 RSP: 00007ffde2b50070 RFLAGS: 00010206 RAX: 0000000000015f41 RBX: 00007f43e97a1b20 RCX: 0000000000000111 RDX: 00000000011affb0 RSI: 00000000011b00c0 RDI: 0000000000000000 RBP: 0000000000000111 R8: 00007f43e97a1bd8 R9: 0000000000000000 R10: 00007f43e97a1b78 R11: 00007f43e97a1b78 R12: 00007f43e97a1b78 R13: 00007f43e97a1b78 R14: 0000000000002710 R15: 00007f43e97a1c78 ORIG_RAX: ffffffffffffffff CS: 0033 SS: 002b
Which is waiting on a lock held by CPU owned by CPU 9: crash> struct raw_spinlock_t ffff99b67b763f40 struct raw_spinlock_t { raw_lock = { { val = { counter = 1 }, { locked = 1 '\001', pending = 0 '\000' }, { locked_pending = 1, tail = 0 } } }, magic = 3735899821, owner_cpu = 9, owner = 0xffff99b66e7a8000, dep_map = { key = 0xffffffff9331d120, class_cache = {0xffffffff93a13da0, 0x0}, name = 0xffffffff92a7d9ad "&rq->lock" } }
Which is hanging out in update_blocked_averages: crash> bt PID: 0 TASK: ffff99b66e7a8000 CPU: 9 COMMAND: "swapper/9" #0 [fffffe0000194e38] crash_nmi_callback at ffffffff91a54202 #1 [fffffe0000194e50] nmi_handle at ffffffff91a32ee2 #2 [fffffe0000194ea0] default_do_nmi at ffffffff91a33362 #3 [fffffe0000194ec0] do_nmi at ffffffff91a33553 #4 [fffffe0000194ef0] end_repeat_nmi at ffffffff924014e8 [exception RIP: lock_is_held_type+70] RIP: ffffffff91aecec6 RSP: ffff99b67b443e20 RFLAGS: 00000046 RAX: 0000000000000001 RBX: ffff99b66e7a8000 RCX: 00000000000000a8 RDX: 0000000000000001 RSI: 00000000ffffffff RDI: 0000000000000046 RBP: 0000000000000046 R8: 0000000000000004 R9: 0000000000000000 R10: ffff99b67b443e38 R11: ffffffff91aca4a7 R12: ffff99b67b763f40 R13: ffff99b67b764940 R14: 0000000000000000 R15: ffff99b6193d9200 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 --- <NMI exception stack> --- #5 [ffff99b67b443e20] lock_is_held_type at ffffffff91aecec6 #6 [ffff99b67b443e30] update_blocked_averages at ffffffff91aca841 #7 [ffff99b67b443ec8] update_nohz_stats at ffffffff91acaa3d #8 [ffff99b67b443ed8] _nohz_idle_balance at ffffffff91ad39f7 #9 [ffff99b67b443f70] __softirqentry_text_start at ffffffff926000d1 #10 [ffff99b67b443fd0] irq_exit at ffffffff91a911f5 #11 [ffff99b67b443fd8] smp_apic_timer_interrupt at ffffffff92402b2c #12 [ffff99b67b443ff0] apic_timer_interrupt at ffffffff92401a9f --- <IRQ stack> --- #13 [ffffa49f98993df8] apic_timer_interrupt at ffffffff92401a9f [exception RIP: mwait_idle+108] RIP: ffffffff923c02fc RSP: ffffa49f98993ea8 RFLAGS: 00000246 RAX: 0000000000000000 RBX: 0000000000000009 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffff99b66e7a8000 RBP: 0000000000000009 R8: 0000000000000001 R9: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff99b66e7a8000 R13: 0000000000000000 R14: 0000000000000000 R15: ffff99b66e7a8000 ORIG_RAX: ffffffffffffff13 CS: 0010 SS: 0018 #14 [ffffa49f98993ec0] do_idle at ffffffff91ac6ba3 #15 [ffffa49f98993f10] cpu_startup_entry at ffffffff91ac6f4f #16 [ffffa49f98993f30] start_secondary at ffffffff91a55759 #17 [ffffa49f98993f50] secondary_startup_64 at ffffffff91a000d4
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Lockdep tells me nothing, which makes me think, somehow is the code in for_each_leaf_cfs_rq_safe looping forever?
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