RHEL7: 长时间运行的 shrink_dentry_list 导致 CPU、软锁定或 rcu_sched 自我检测卡住，当审计启用了，并有许多进程在同一目录中执行基于路径的系统调用时

Issue

长时间运行的 shrink_dentry_list 看到 BUG: soft lockup 或 rcu_sched self-detected stall 消息

[909563.904619] NMI watchdog: BUG: soft lockup - CPU#8 stuck for 22s! [hpsensor:98289]
[909563.904625] Modules linked in: btrfs zlib_deflate raid6_pq xor msdos bnx2i cnic uio fuse rpcrdma ib_isert iscsi_target_mod ib_iser libiscsi ib_srpt target_core_mod ib_srp scsi_transport_srp rdma_ucm ib_ucm ib_uverbs ib_umad rdma_cm iw_cm ib_ipoib ib_cm mlx4_ib ib_core mlx4_en mlx4_core devlink binfmt_misc rpcsec_gss_krb5 nfsv4 dns_resolver nfs fscache scsi_transport_iscsi nf_conntrack_ftp ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 bonding ipt_REJECT nf_reject_ipv4 xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw iptable_filter
[909563.904704]  ext4 mbcache jbd2 vfat fat intel_powerclamp coretemp kvm_intel kvm irqbypass crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd pcspkr osst iTCO_wdt iTCO_vendor_support ses enclosure scsi_transport_sas st ch sg sb_edac hpilo hpwdt edac_core ioatdma lpc_ich dca shpchp ipmi_devintf ipmi_si ipmi_msghandler nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs dm_service_time sd_mod crc_t10dif crct10dif_generic dm_multipath crct10dif_pclmul crct10dif_common crc32c_intel mgag200 qla2xxx i2c_algo_bit bnx2x drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm scsi_transport_fc scsi_tgt mdio ptp i2c_core pps_core libcrc32c dm_mirror dm_region_hash dm_log dm_mod
[909563.904781] CPU: 8 PID: 98289 Comm: hpsensor Tainted: G        W    L ------------   3.10.0-552.el7.wd2.x86_64 #1
[909563.904783] Hardware name: HP Superdome2 16s x86, BIOS Bundle: 008.004.084 SFW: 043.025.000 08/16/2016
[909563.904785] task: ffff88a9aa21bec0 ti: ffff88a1e7aec000 task.ti: ffff88a1e7aec000
[909563.904787] RIP: 0010:[<ffffffff8168ce7e>]  [<ffffffff8168ce7e>] _raw_spin_lock+0xe/0x50
[909563.904796] RSP: 0018:ffff88a1e7aef940  EFLAGS: 00000202
[909563.904798] RAX: 00000000232a232a RBX: ffff88daa8e8c540 RCX: 0000000000008f0a
[909563.904799] RDX: ffff88e592b72920 RSI: 00000000000094e2 RDI: ffff88daa8e8c598
[909563.904800] RBP: ffff88a1e7aef990 R08: ffff88de47500980 R09: 0000000000010360
[909563.904802] R10: ffff88daa8e8c540 R11: ffffea03fdd84f80 R12: ffff88a5eeba6e40
[909563.904803] R13: ffff88a1e7aef938 R14: 00000000b01bb6a5 R15: ffff88a1e7aef938
[909563.904805] FS:  00007f8573efe700(0000) GS:ffff881fffc00000(0000) knlGS:0000000000000000
[909563.904806] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[909563.904807] CR2: 0000000000b4c6c0 CR3: 00000009ae203000 CR4: 00000000001407e0
[909563.904809] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[909563.904810] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[909563.904811] Stack:
[909563.904812]  ffffffff81213c1f ffff88daa8e8c540 ffff88e592b72920 ffff88daa8e8c5c0
[909563.904815]  00000000b01bb6a5 ffff890053b8c800 ffff88c05399bf18 0000000000000000
[909563.904817]  ffff890053b8c8d0 ffff88c05399bf40 ffff88a1e7aef9f0 ffffffff812144ee
[909563.904820] Call Trace:
[909563.904825]  [<ffffffff81213c1f>] ? shrink_dentry_list+0x4f/0x480
[909563.904828]  [<ffffffff812144ee>] prune_dcache_sb+0x13e/0x180
[909563.904832]  [<ffffffff811fd7c8>] prune_super+0x138/0x170
[909563.904837]  [<ffffffff81191a33>] shrink_slab+0x163/0x330
[909563.904842]  [<ffffffff811f21d7>] ? vmpressure+0x87/0x90
[909563.904845]  [<ffffffff81194851>] zone_reclaim+0x1d1/0x2f0
[909563.904849]  [<ffffffff81188034>] get_page_from_freelist+0x2c4/0x9f0
[909563.904853]  [<ffffffff811888f7>] __alloc_pages_nodemask+0x197/0xbc0
[909563.904858]  [<ffffffff811cf1da>] alloc_pages_vma+0x9a/0x150
[909563.904862]  [<ffffffff811ae49f>] handle_mm_fault+0xc6f/0xfe0
[909563.904866]  [<ffffffff816910b4>] __do_page_fault+0x154/0x450
[909563.904868]  [<ffffffff816913e5>] do_page_fault+0x35/0x90
[909563.904871]  [<ffffffff8168d5c8>] page_fault+0x28/0x30
[909563.904872] Code: e8 01 74 0a 0f b7 0f 66 39 ca 75 f1 5d c3 0f 1f 80 00 00 00 00 eb dc 66 0f 1f 44 00 00 0f 1f 44 00 00 b8 00 00 02 00 f0 0f c1 07 <89> c2 c1 ea 10 66 39 c2 75 01 c3 55 83 e2 fe 0f b7 f2 48 89 e5
[909568.756771] INFO: rcu_sched self-detected stall on CPU { 8}  (t=60001 jiffies g=86912459 c=86912458 q=25025260)
[909568.756797] Task dump for CPU 8:
[909568.756800] hpsensor        R  running task        0 98289  95549 0x0000008a
[909568.756803]  ffff88a9aa21bec0 00000000b01bb6a5 ffff881fffc03db0 ffffffff810c1158
[909568.756806]  0000000000000008 ffffffff81a24480 ffff881fffc03dc8 ffffffff810c4a99
[909568.756808]  0000000000000009 ffff881fffc03df8 ffffffff81134060 ffff881fffc10240
[909568.756810] Call Trace:
[909568.756812]  <IRQ>  [<ffffffff810c1158>] sched_show_task+0xa8/0x110
[909568.756829]  [<ffffffff810c4a99>] dump_cpu_task+0x39/0x70
[909568.756834]  [<ffffffff81134060>] rcu_dump_cpu_stacks+0x90/0xd0
[909568.756837]  [<ffffffff811377b2>] rcu_check_callbacks+0x442/0x730
[909568.756845]  [<ffffffff810eff40>] ? tick_sched_handle.isra.13+0x60/0x60
[909568.756852]  [<ffffffff81097457>] update_process_times+0x47/0x80
[909568.756854]  [<ffffffff810eff05>] tick_sched_handle.isra.13+0x25/0x60
[909568.756857]  [<ffffffff810eff81>] tick_sched_timer+0x41/0x70
[909568.756861]  [<ffffffff810b2592>] __hrtimer_run_queues+0xd2/0x260
[909568.756864]  [<ffffffff810b2b30>] hrtimer_interrupt+0xb0/0x1e0
[909568.756868]  [<ffffffff81697b5c>] ? call_softirq+0x1c/0x30
[909568.756872]  [<ffffffff81050007>] local_apic_timer_interrupt+0x37/0x60
[909568.756875]  [<ffffffff816987cf>] smp_apic_timer_interrupt+0x3f/0x60
[909568.756877]  [<ffffffff81696d1d>] apic_timer_interrupt+0x6d/0x80
[909568.756879]  <EOI>  [<ffffffff8168cd0b>] ? _raw_spin_trylock+0xb/0x40
[909568.756889]  [<ffffffff81213ca2>] shrink_dentry_list+0xd2/0x480
[909568.756891]  [<ffffffff812144ee>] prune_dcache_sb+0x13e/0x180
[909568.756896]  [<ffffffff811fd7c8>] prune_super+0x138/0x170
[909568.756900]  [<ffffffff81191a33>] shrink_slab+0x163/0x330
[909568.756905]  [<ffffffff811f21d7>] ? vmpressure+0x87/0x90
[909568.756907]  [<ffffffff81194851>] zone_reclaim+0x1d1/0x2f0
[909568.756913]  [<ffffffff81188034>] get_page_from_freelist+0x2c4/0x9f0
[909568.756915]  [<ffffffff811888f7>] __alloc_pages_nodemask+0x197/0xbc0
[909568.756921]  [<ffffffff811cf1da>] alloc_pages_vma+0x9a/0x150
[909568.756926]  [<ffffffff811ae49f>] handle_mm_fault+0xc6f/0xfe0
[909568.756933]  [<ffffffff816910b4>] __do_page_fault+0x154/0x450
[909568.756936]  [<ffffffff816913e5>] do_page_fault+0x35/0x90
[909568.756938]  [<ffffffff8168d5c8>] page_fault+0x28/0x30