INFO: rcu detected stall in find_vma

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b850307b Linux 4.14.184
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1514506b100000
kernel config: https://syzkaller.appspot.com/x/.config?x=ddc0f08dd6b981c5
dashboard link: https://syzkaller.appspot.com/bug?extid=f50b57e1a6f99410c2fe
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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+f50b57...@syzkaller.appspotmail.com

INFO: rcu_sched detected stalls on CPUs/tasks:
(detected by 0, t=10502 jiffies, g=3137, c=3136, q=0)
All QSes seen, last rcu_sched kthread activity 10502 (4294980896-4294970394), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.3 R running task 29024 17068 6351 0x00000000
Call Trace:
<IRQ>
sched_show_task kernel/sched/core.c:5168 [inline]
sched_show_task.cold+0x335/0x399 kernel/sched/core.c:5143
print_other_cpu_stall kernel/rcu/tree.c:1501 [inline]
check_cpu_stall kernel/rcu/tree.c:1616 [inline]
__rcu_pending kernel/rcu/tree.c:3390 [inline]
rcu_pending kernel/rcu/tree.c:3452 [inline]
rcu_check_callbacks.cold+0xd3f/0xdaa kernel/rcu/tree.c:2792
update_process_times+0x29/0x60 kernel/time/timer.c:1590
tick_sched_handle.isra.0+0x73/0x150 kernel/time/tick-sched.c:165
tick_sched_timer+0x41/0x120 kernel/time/tick-sched.c:1223
__run_hrtimer kernel/time/hrtimer.c:1223 [inline]
__hrtimer_run_queues+0x24b/0xb90 kernel/time/hrtimer.c:1287
hrtimer_interrupt+0x1e6/0x5e0 kernel/time/hrtimer.c:1321
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline]
smp_apic_timer_interrupt+0x117/0x5f0 arch/x86/kernel/apic/apic.c:1100
apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:793
</IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x9/0x50 kernel/kcov.c:65
RSP: 0000:ffff8881c9237e40 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: ffff88809260a0c0 RBX: 0000000000000002 RCX: ffffc90007101000
RDX: 0000000000040000 RSI: ffffffff8177edf6 RDI: ffff88809fba3da8
RBP: dffffc0000000000 R08: 0000000000000001 R09: 00000000000583e5
R10: ffff88809260a948 R11: ffff88809260a0c0 R12: ffff88809fba3d68
R13: ffff88805b527980 R14: 0000000023b13ce8 R15: ffff88809260a0c0
vmacache_find+0x125/0x260 mm/vmacache.c:66
find_vma+0x1c/0x140 mm/mmap.c:2149
__do_page_fault+0x32d/0xb50 arch/x86/mm/fault.c:1388
page_fault+0x45/0x50 arch/x86/entry/entry_64.S:1123
RIP: 0c38:0x4ce8ad
RSP: 50a400:000000000078bf00 EFLAGS: ffffffff
rcu_sched kthread starved for 10502 jiffies! g3137 c3136 f0x2 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
rcu_sched R running task 29904 9 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x8a6/0x1d70 kernel/sched/core.c:3384
schedule+0x8d/0x1b0 kernel/sched/core.c:3428
schedule_timeout+0x4df/0xe50 kernel/time/timer.c:1746
rcu_gp_kthread+0xb3d/0x1ce0 kernel/rcu/tree.c:2255
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
INFO: rcu_preempt detected stalls on CPUs/tasks:
Tasks blocked on level-0 rcu_node (CPUs 0-1): P3637
(detected by 0, t=10527 jiffies, g=5558, c=5557, q=287)
systemd-udevd R running task 26320 3637 1 0x00000100
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x8a6/0x1d70 kernel/sched/core.c:3384
preempt_schedule_notrace+0x99/0x120 kernel/sched/core.c:3582
___preempt_schedule_notrace+0x16/0x27
rcu_is_watching+0x87/0xb0 kernel/rcu/tree.c:1131
rcu_read_lock include/linux/rcupdate.h:630 [inline]
__d_lookup+0x4a8/0x670 fs/dcache.c:2326
lookup_fast+0x31f/0xe60 fs/namei.c:1641
walk_component+0xc0/0xbc0 fs/namei.c:1821
link_path_walk+0x80a/0x1080 fs/namei.c:2154
path_lookupat.isra.0+0xcb/0x7b0 fs/namei.c:2342
filename_lookup+0x18e/0x380 fs/namei.c:2377
user_path_at include/linux/namei.h:57 [inline]
vfs_statx+0xd1/0x160 fs/stat.c:185
vfs_lstat include/linux/fs.h:3066 [inline]
SYSC_newlstat fs/stat.c:350 [inline]
SyS_newlstat+0x83/0xe0 fs/stat.c:344
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f542da05335
RSP: 002b:00007ffc393abe08 EFLAGS: 00000246 ORIG_RAX: 0000000000000006
RAX: ffffffffffffffda RBX: 000055b06e7205d0 RCX: 00007f542da05335
RDX: 00007ffc393abe40 RSI: 00007ffc393abe40 RDI: 000055b06e71f5d0
RBP: 00007ffc393abf00 R08: 00007f542dcc41a8 R09: 0000000000001010
R10: 0000000000000020 R11: 0000000000000246 R12: 000055b06e71f5d0
R13: 000055b06e71f5ea R14: 000055b06e71ee15 R15: 000055b06e71ee1a
systemd-udevd R running task 26320 3637 1 0x00000100
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x8a6/0x1d70 kernel/sched/core.c:3384
preempt_schedule_notrace+0x99/0x120 kernel/sched/core.c:3582
___preempt_schedule_notrace+0x16/0x27
rcu_is_watching+0x87/0xb0 kernel/rcu/tree.c:1131
rcu_read_lock include/linux/rcupdate.h:630 [inline]
__d_lookup+0x4a8/0x670 fs/dcache.c:2326
lookup_fast+0x31f/0xe60 fs/namei.c:1641
walk_component+0xc0/0xbc0 fs/namei.c:1821
link_path_walk+0x80a/0x1080 fs/namei.c:2154
path_lookupat.isra.0+0xcb/0x7b0 fs/namei.c:2342
filename_lookup+0x18e/0x380 fs/namei.c:2377
user_path_at include/linux/namei.h:57 [inline]
vfs_statx+0xd1/0x160 fs/stat.c:185
vfs_lstat include/linux/fs.h:3066 [inline]
SYSC_newlstat fs/stat.c:350 [inline]
SyS_newlstat+0x83/0xe0 fs/stat.c:344
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f542da05335
RSP: 002b:00007ffc393abe08 EFLAGS: 00000246 ORIG_RAX: 0000000000000006
RAX: ffffffffffffffda RBX: 000055b06e7205d0 RCX: 00007f542da05335
RDX: 00007ffc393abe40 RSI: 00007ffc393abe40 RDI: 000055b06e71f5d0
RBP: 00007ffc393abf00 R08: 00007f542dcc41a8 R09: 0000000000001010
R10: 0000000000000020 R11: 0000000000000246 R12: 000055b06e71f5d0
R13: 000055b06e71f5ea R14: 000055b06e71ee15 R15: 000055b06e71ee1a
rcu_preempt kthread starved for 10527 jiffies! g5558 c5557 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
rcu_preempt R running task 29472 8 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2808 [inline]
__schedule+0x8a6/0x1d70 kernel/sched/core.c:3384
schedule+0x8d/0x1b0 kernel/sched/core.c:3428
schedule_timeout+0x4df/0xe50 kernel/time/timer.c:1746
rcu_gp_kthread+0xb3d/0x1ce0 kernel/rcu/tree.c:2255
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404


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[syzbot]

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