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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] 4.4: INFO: rcu_sched self-detected stall on CPU
On 26/03/2016 1:44 AM, Boris Ostrovsky wrote: > On 03/25/2016 10:05 AM, Steven Haigh wrote: >> On 25/03/2016 11:23 PM, Boris Ostrovsky wrote: >>> On 03/24/2016 10:53 PM, Steven Haigh wrote: >>>> Hi all, >>>> >>>> Firstly, I've cross-posted this to xen-devel and the lkml - as this >>>> problem seems to only exist when using kernel 4.4 as a Xen DomU kernel. >>>> I have also CC'ed Greg KH for his awesome insight as maintainer. >>>> >>>> Please CC myself into replies - as I'm not a member of the kernel >>>> mailing list - I may miss replies from monitoring the archives. >>>> >>>> I've noticed recently that heavy disk IO is causing rcu_sched to detect >>>> stalls. The process mentioned usually goes to 100% CPU usage, and >>>> eventually processes start segfaulting and dying. The only fix to >>>> recover the system is to use 'xl destroy' to force-kill the VM and to >>>> start it again. >>>> >>>> The majority of these issues seem to mention ext4 in the trace. This >>>> may >>>> indicate an issue there - or may be a red herring. >>>> >>>> The gritty details: >>>> INFO: rcu_sched self-detected stall on CPU >>>> #0110-...: (20999 ticks this GP) idle=327/140000000000001/0 >>>> softirq=1101493/1101493 fqs=6973 >>>> #011 (t=21000 jiffies g=827095 c=827094 q=524) >>>> Task dump for CPU 0: >>>> rsync R running task 0 2446 2444 0x00000088 >>>> ffffffff818d0c00 ffff88007fc03c58 ffffffff810a625f 0000000000000000 >>>> ffffffff818d0c00 ffff88007fc03c70 ffffffff810a8699 0000000000000001 >>>> ffff88007fc03ca0 ffffffff810d0e5a ffff88007fc170c0 ffffffff818d0c00 >>>> Call Trace: >>>> <IRQ> [<ffffffff810a625f>] sched_show_task+0xaf/0x110 >>>> [<ffffffff810a8699>] dump_cpu_task+0x39/0x40 >>>> [<ffffffff810d0e5a>] rcu_dump_cpu_stacks+0x8a/0xc0 >>>> [<ffffffff810d4884>] rcu_check_callbacks+0x424/0x7a0 >>>> [<ffffffff810a91e1>] ? account_system_time+0x81/0x110 >>>> [<ffffffff810a9481>] ? account_process_tick+0x61/0x160 >>>> [<ffffffff810e8050>] ? tick_sched_do_timer+0x30/0x30 >>>> [<ffffffff810d9749>] update_process_times+0x39/0x60 >>>> [<ffffffff810e7aa6>] tick_sched_handle.isra.15+0x36/0x50 >>>> [<ffffffff810e808d>] tick_sched_timer+0x3d/0x70 >>>> [<ffffffff810da342>] __hrtimer_run_queues+0xf2/0x250 >>>> [<ffffffff810da698>] hrtimer_interrupt+0xa8/0x190 >>>> [<ffffffff8100c61e>] xen_timer_interrupt+0x2e/0x140 >>>> [<ffffffff810c8555>] handle_irq_event_percpu+0x55/0x1e0 >>>> [<ffffffff810cbbca>] handle_percpu_irq+0x3a/0x50 >>>> [<ffffffff810c7d22>] generic_handle_irq+0x22/0x30 >>>> [<ffffffff813e50ff>] __evtchn_fifo_handle_events+0x15f/0x180 >>>> [<ffffffff813e5130>] evtchn_fifo_handle_events+0x10/0x20 >>>> [<ffffffff813e2233>] __xen_evtchn_do_upcall+0x43/0x80 >>>> [<ffffffff813e3ea0>] xen_evtchn_do_upcall+0x30/0x50 >>>> [<ffffffff8165deb2>] xen_hvm_callback_vector+0x82/0x90 >>>> <EOI> [<ffffffff810baf0d>] ? queued_write_lock_slowpath+0x3d/0x80 >>>> [<ffffffff8165bcce>] _raw_write_lock+0x1e/0x30 >>> This looks to me like ext4 failing to grab a lock. Everything above it >>> (in Xen code) is regular tick interrupt handling which detects the >>> stall. >>> >>> Your config does not have CONFIG_PARAVIRT_SPINLOCKS so that eliminates >>> any possible issues with pv locks. >>> >>> Do you see anything "interesting" in dom0? (e.g. dmesg, xl dmesg, >>> /var/log/xen/) Are you oversubscribing your guest (CPU-wise)? >> There is nothing special being logged anywhere that I can see. dmesg / >> xl dmesg on the Dom0 show nothing unusual. >> >> I do share CPUs - but I don't give any DomU more than 2 vcpus. The >> physical host has 4 cores - 1 pinned to the Dom0. >> >> I log to a remote syslog on this system - and I've uploaded the entire >> log to a pastebin (don't want to do a 45Kb attachment here): >> http://paste.fedoraproject.org/345095/58914452 > > That doesn't look like a full log. In any case, the RCU stall may be a > secondary problem --- there is a bunch of splats before the stall. It may not actually be the full logs. Once the system gets really upset, you can't run anything - as such, grabbing anything from dmesg is not possible. The logs provided above is all that gets spat out to the syslog server. I'll try tinkering with a few things to see if I can get more output - but right now, that's all I've been able to achieve. So far, my only ideas are to remove the 'quiet' options from the kernel command line - but I'm not sure how much that would help. Suggestions gladly accepted on this front. >> >> Not sure if it makes any difference at all, but my DomU config is: >> # cat /etc/xen/backup.vm >> name = "backup.vm" >> memory = 2048 >> vcpus = 2 >> cpus = "1-3" >> disk = [ 'phy:/dev/vg_raid1_new/backup.vm,xvda,w' ] >> vif = [ "mac=00:11:36:35:35:09, bridge=br203, >> vifname=vm.backup, script=vif-bridge" ] >> bootloader = 'pygrub' >> pvh = 1 >> >> on_poweroff = 'destroy' >> on_reboot = 'restart' >> on_crash = 'restart' >> cpu_weight = 64 >> >> I never had this problem when running kernel 4.1.x - it only started >> when I upgraded everything to 4.4 - not exactly a great help - but may >> help narrow things down? >> >>>> [<ffffffff81289b23>] ext4_es_remove_extent+0x43/0xc0 >>>> [<ffffffff812692f9>] ext4_clear_inode+0x39/0x80 >>>> [<ffffffff8124cafd>] ext4_evict_inode+0x8d/0x4e0 >>>> [<ffffffff811df537>] evict+0xb7/0x180 >>>> [<ffffffff811df636>] dispose_list+0x36/0x50 >>>> [<ffffffff811e054b>] prune_icache_sb+0x4b/0x60 >>>> [<ffffffff811c92c1>] super_cache_scan+0x141/0x190 >>>> [<ffffffff811655fe>] shrink_slab.part.37+0x1ee/0x390 >>>> [<ffffffff8116950c>] shrink_zone+0x26c/0x280 >>>> [<ffffffff8116988c>] do_try_to_free_pages+0x15c/0x410 >>>> [<ffffffff81169bfa>] try_to_free_pages+0xba/0x170 >>>> [<ffffffff8115d1e5>] __alloc_pages_nodemask+0x525/0xa60 >>>> [<ffffffff811a839c>] ? kmem_cache_free+0xcc/0x2c0 >>>> [<ffffffff811a120d>] alloc_pages_current+0x8d/0x120 >>>> [<ffffffff81154601>] __page_cache_alloc+0x91/0xc0 >>>> [<ffffffff81154b66>] pagecache_get_page+0x56/0x1e0 >>>> [<ffffffff81154ee6>] grab_cache_page_write_begin+0x26/0x40 >>>> [<ffffffff8124c811>] ext4_da_write_begin+0xa1/0x300 >>>> [<ffffffff8124d3a4>] ? ext4_da_write_end+0x124/0x2b0 >>>> [<ffffffff811543a0>] generic_perform_write+0xc0/0x1a0 >>>> [<ffffffff81156408>] __generic_file_write_iter+0x188/0x1e0 >>>> [<ffffffff812421d0>] ext4_file_write_iter+0xf0/0x340 >>>> [<ffffffff811c59fa>] __vfs_write+0xaa/0xe0 >>>> [<ffffffff811c6022>] vfs_write+0xa2/0x1a0 >>>> [<ffffffff811c6d26>] SyS_write+0x46/0xa0 >>>> [<ffffffff8165c02e>] entry_SYSCALL_64_fastpath+0x12/0x71 >>>> >>>> Some 11 hours later: >>>> sshd[785]: segfault at 1f0 ip 00007f03bb94ae5c sp 00007ffe9eb54470 >>>> error >>>> 4 in ld-2.17.so[7f03bb940000+21000] >>>> sh[787]: segfault at 1f0 ip 00007f6b4a0dfe5c sp 00007ffe3d4a71e0 >>>> error 4 >>>> in ld-2.17.so[7f6b4a0d5000+21000] >>>> systemd-cgroups[788]: segfault at 1f0 ip 00007f4baa82ce5c sp >>>> 00007ffd28e4c4b0 error 4 in ld-2.17.so[7f4baa822000+21000] >>>> sshd[791]: segfault at 1f0 ip 00007ff8c8a8ce5c sp 00007ffede9e1c20 >>>> error >>>> 4 in ld-2.17.so[7ff8c8a82000+21000] >>>> sshd[792]: segfault at 1f0 ip 00007f183cf75e5c sp 00007ffc81ab7160 >>>> error >>>> 4 in ld-2.17.so[7f183cf6b000+21000] >>>> sshd[793]: segfault at 1f0 ip 00007f3c665ece5c sp 00007ffd9a13c850 >>>> error >>>> 4 in ld-2.17.so[7f3c665e2000+21000] >>>> >>>> From isolated testing, this does not occur on kernel 4.5.x - >>>> however I >>>> have not verified this myself. >>>> >>>> The kernel config used can be found in the kernel-xen git repo if it >>>> assists in debugging: >>>> http://xen.crc.id.au/git/?p=kernel-xen;a=summary >>>> >>>> >>>> >>>> _______________________________________________ >>>> Xen-devel mailing list >>>> Xen-devel@xxxxxxxxxxxxx >>>> http://lists.xen.org/xen-devel > -- Steven Haigh Email: netwiz@xxxxxxxxx Web: https://www.crc.id.au Phone: (03) 9001 6090 - 0412 935 897 Attachment:
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