INFO: rcu detected stall in wp_page_copy

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 18b8bfa7c63b Add linux-next specific files for 20180828
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=14ba176a400000
kernel config: https://syzkaller.appspot.com/x/.config?x=29f635fa875f8ab1
dashboard link: https://syzkaller.appspot.com/bug?extid=6b46a6efe0d161573996
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [ak...@linux-foundation.org dan.j.w...@intel.com
jgl...@redhat.com jrdr....@gmail.com kirill....@linux.intel.com
linux-...@vger.kernel.org linu...@kvack.org mho...@suse.com
min...@kernel.org pet...@infradead.org ri...@surriel.com
ying....@intel.com zwi...@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+6b46a6...@syzkaller.appspotmail.com

RAX: ffffffffffffffda RBX: 00007fd9bf18b6d4 RCX: 0000000000410dc1
RDX: 00007fd9bf18abdf RSI: 0000000000000002 RDI: 00007fd9bf18abd0
RBP: 00000000009300a0 R08: 0000000000000000 R09: 000000000000000f
R10: 0000000000000004 R11: 0000000000000293 R12: 0000000000000004
R13: 00000000004d6b70 R14: 00000000004ca09a R15: 0000000000000000
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 1-...!: (1 ticks this GP) idle=a86/1/0x4000000000000002
softirq=55911/55911 fqs=0
rcu: (t=111999 jiffies g=108637 q=251)
rcu: rcu_sched kthread starved for 111999 jiffies! g108637 f0x0
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_sched R running task 23480 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2825 [inline]
__schedule+0x87c/0x1df0 kernel/sched/core.c:3473
schedule+0xfb/0x450 kernel/sched/core.c:3517
schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
rcu_gp_kthread+0x743/0x1d20 kernel/rcu/tree.c:2194
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
NMI backtrace for cpu 1
CPU: 1 PID: 4474 Comm: syz-fuzzer Not tainted 4.19.0-rc1-next-20180828+ #49
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.3+0x48/0x88 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_single_cpu_backtrace include/linux/nmi.h:162 [inline]
rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1340
print_cpu_stall.cold.78+0x2fb/0x59c kernel/rcu/tree.c:1478
check_cpu_stall kernel/rcu/tree.c:1550 [inline]
__rcu_pending kernel/rcu/tree.c:3276 [inline]
rcu_pending kernel/rcu/tree.c:3319 [inline]
rcu_check_callbacks+0xd4a/0x15a0 kernel/rcu/tree.c:2665
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/0xff0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1029 [inline]
smp_apic_timer_interrupt+0x16d/0x6a0 arch/x86/kernel/apic/apic.c:1054
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
</IRQ>
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:31 [inline]
RIP: 0010:atomic_read include/asm-generic/atomic-instrumented.h:22 [inline]
RIP: 0010:virt_spin_lock arch/x86/include/asm/qspinlock.h:65 [inline]
RIP: 0010:native_queued_spin_lock_slowpath+0x1a2/0x1220
kernel/locking/qspinlock.c:305
Code: ff 4d 01 f4 be 04 00 00 00 4c 89 ff e8 67 8d 5b 00 4c 89 f8 41 c6 04
24 04 48 c1 e8 03 42 0f b6 04 30 38 85 f0 fb ff ff 7c 08 <84> c0 0f 85 29
0b 00 00 41 0f b6 34 24 45 8b 2f 40 84 f6 74 0a 40
RSP: 0000:ffff8801abdf71a8 EFLAGS: 00000206 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: ffff8801abdf75b0 RCX: ffffffff81603bd9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8801b0e74000
RBP: ffff8801abdf75d8 R08: ffffed00361ce801 R09: ffffed00361ce800
R10: ffffed00361ce800 R11: ffff8801b0e74003 R12: ffffed00357bee96
R13: 0000000000000001 R14: dffffc0000000000 R15: ffff8801b0e74000
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:679 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:32 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:88 [inline]
do_raw_spin_lock+0x1a7/0x200 kernel/locking/spinlock_debug.c:113
__raw_spin_lock include/linux/spinlock_api_smp.h:143 [inline]
_raw_spin_lock+0x32/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
wp_page_copy+0x500/0x12c0 mm/memory.c:2524
do_wp_page+0x875/0x1800 mm/memory.c:2793
handle_pte_fault mm/memory.c:3999 [inline]
__handle_mm_fault+0x2931/0x4350 mm/memory.c:4107
handle_mm_fault+0x53e/0xc80 mm/memory.c:4144
__do_page_fault+0x620/0xe50 arch/x86/mm/fault.c:1395
do_page_fault+0xf6/0x7a4 arch/x86/mm/fault.c:1470
page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1164
RIP: 0033:0x41e331
Code: 0f 95 c7 44 89 c9 e9 ec fe ff ff 8b 0d 34 47 06 01 85 c9 7e 09 48 8b
4b 30 49 39 c8 73 42 84 07 41 0f b6 0c 31 44 84 d1 75 2c <f0> 44 08 17 0f
b6 4b 62 f6 c1 01 0f 84 04 ff ff ff 48 8b 44 24 60
RSP: 002b:000000c420155828 EFLAGS: 00010246
RAX: 000000c42f0ae4c0 RBX: 00007f2db1af4098 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 00007f2da8a5ae90 RDI: 00007f2da8a5ae92
RBP: 000000c420155848 R08: 0000000000000013 R09: 0000000000000002
R10: 0000000000000008 R11: 0000000000020414 R12: 0000000000b7cde0
R13: 0000000000b241a8 R14: 000000c435123b78 R15: 0000000000000000


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[syzbot]

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