INFO: rcu detected stall in irq_exit

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 29119529d8de Merge tag 'for-linus-20180706' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=133d16fc400000
kernel config: https://syzkaller.appspot.com/x/.config?x=2ca6c7a31d407f86
dashboard link: https://syzkaller.appspot.com/bug?extid=b86c0bfe1b4ebf4487fb
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [b...@suse.de fanwen...@gmail.com h...@zytor.com
jgr...@suse.com linux-...@vger.kernel.org lu...@kernel.org
mhke...@outlook.com mi...@redhat.com pbon...@redhat.com
tg...@linutronix.de vkuz...@redhat.com x...@kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b86c0b...@syzkaller.appspotmail.com

FAT-fs (loop3): Directory bread(block 2567) failed
INFO: rcu_sched detected stalls on CPUs/tasks:
(detected by 1, t=300078 jiffies, g=59116, c=59115, q=66)
All QSes seen, last rcu_sched kthread activity 300078
(4295401045-4295100967), jiffies_till_next_fqs=3, root ->qsmask 0x0
syz-executor0 R running task 23416 26005 23698 0x00000008
Call Trace:
<IRQ>
sched_show_task.cold.84+0x27a/0x301 kernel/sched/core.c:5327
print_other_cpu_stall.cold.77+0x92f/0x9d2 kernel/rcu/tree.c:1441
check_cpu_stall.isra.60+0x721/0xf70 kernel/rcu/tree.c:1559
__rcu_pending kernel/rcu/tree.c:3244 [inline]
rcu_pending kernel/rcu/tree.c:3291 [inline]
rcu_check_callbacks+0x23f/0xcd0 kernel/rcu/tree.c:2646
update_process_times+0x2d/0x70 kernel/time/timer.c:1636
tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164
tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x3eb/0x10c0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1050
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
RIP: 0010:arch_local_irq_enable arch/x86/include/asm/paravirt.h:793 [inline]
RIP: 0010:__do_softirq+0x2a0/0xb17 kernel/softirq.c:272
Code: c7 c0 78 b0 f1 88 48 c1 e8 03 42 80 3c 38 00 0f 85 50 07 00 00 48 83
3d e5 ad 31 01 00 0f 84 ab 06 00 00 fb 66 0f 1f 44 00 00 <48> c7 85 68 fe
ff ff 00 91 e0 88 b8 ff ff ff ff 0f bc 85 74 fe ff
RSP: 0018:ffff8801daf07dc0 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11e360f RBX: ffff8801b9cda040 RCX: 1ffff1003739b513
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8801b9cda874
RBP: ffff8801daf07f98 R08: ffff8801b9cda878 R09: 0000000000000002
R10: ffff8801b9cda040 R11: 0000000000000000 R12: 000000000000002a
R13: ffff8801ce206d80 R14: 000000000000002a R15: dffffc0000000000
invoke_softirq kernel/softirq.c:368 [inline]
irq_exit+0x1d1/0x200 kernel/softirq.c:408
exiting_irq arch/x86/include/asm/apic.h:527 [inline]
do_IRQ+0xf1/0x190 arch/x86/kernel/irq.c:257
common_interrupt+0xf/0xf arch/x86/entry/entry_64.S:642
</IRQ>
RIP: 0010:arch_local_irq_enable arch/x86/include/asm/paravirt.h:793 [inline]
RIP: 0010:vcpu_enter_guest+0x2689/0x6090 arch/x86/kvm/x86.c:7432
Code: 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 f8 2e 00 00 48 83 3d 21 36 e3 07
00 0f 84 5b 19 00 00 e8 6e 91 6d 00 fb 66 0f 1f 44 00 00 <48> b8 00 00 00
00 00 fc ff df 48 89 da 48 c1 ea 03 65 ff 0d 4f 73
RSP: 0018:ffff8801bb4774f0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffd5
RAX: 0000000000040000 RBX: ffff8801cb0f8780 RCX: ffffc90005236000
RDX: 0000000000040000 RSI: ffffffff810e7a62 RDI: ffffffff88f1b078
RBP: ffff8801bb477840 R08: ffff8801b9cda878 R09: 0000000000000006
R10: ffff8801b9cda040 R11: 0000000000000000 R12: ffff8801cb0f87ac
R13: 0000000000000001 R14: ffff8801b9cda040 R15: ffff8801cb0f87b0
vcpu_run arch/x86/kvm/x86.c:7585 [inline]
kvm_arch_vcpu_ioctl_run+0x33e/0x1690 arch/x86/kvm/x86.c:7762
kvm_vcpu_ioctl+0x7b8/0x1300 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2580
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:684
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
__do_sys_ioctl fs/ioctl.c:708 [inline]
__se_sys_ioctl fs/ioctl.c:706 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455ba9
Code: 1d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f89592bbc68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f89592bc6d4 RCX: 0000000000455ba9
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000016
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004bdd70 R14: 00000000004cc310 R15: 0000000000000000
rcu_sched kthread starved for 300078 jiffies! g59116 c59115 f0x2
RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
RCU grace-period kthread stack dump:
rcu_sched R running task 23392 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2862 [inline]
__schedule+0x87c/0x1ed0 kernel/sched/core.c:3504
schedule+0xfb/0x450 kernel/sched/core.c:3548
schedule_timeout+0x140/0x260 kernel/time/timer.c:1801
rcu_gp_kthread+0x717/0x1c90 kernel/rcu/tree.c:2179
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
FAT-fs (loop3): Directory bread(block 2568) failed
FAT-fs (loop3): Directory bread(block 2569) failed
FAT-fs (loop3): Directory bread(block 2570) failed
FAT-fs (loop3): Directory bread(block 2571) failed
FAT-fs (loop3): Directory bread(block 2572) failed
FAT-fs (loop3): Directory bread(block 2573) failed
FAT-fs (loop3): Directory bread(block 2574) failed
FAT-fs (loop3): Directory bread(block 2575) failed
FAT-fs (loop3): Directory bread(block 2576) failed
FAT-fs (loop3): Directory bread(block 2577) failed
FAT-fs (loop3): mounting with "discard" option, but the device does not
support discard


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.