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Subjectpossible deadlock in lock_timer_base
From
Hello,

syzbot found the following issue on:

HEAD commit: d7a03a44 Add linux-next specific files for 20201223
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=155fb7b7500000
kernel config: https://syzkaller.appspot.com/x/.config?x=ea251547cbb170c5
dashboard link: https://syzkaller.appspot.com/bug?extid=8983d6d4f7df556be565
compiler: gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8983d6d4f7df556be565@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.10.0-next-20201223-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/9817 is trying to acquire lock:
ffffffff8b48b998 (allocation_wait.lock){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137

but task is already holding lock:
ffff8880b9e24898 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x5a/0x1f0 kernel/time/timer.c:944

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&base->lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
lock_timer_base+0x5a/0x1f0 kernel/time/timer.c:944
__mod_timer+0x398/0xe30 kernel/time/timer.c:1017
__queue_delayed_work+0x1a7/0x270 kernel/workqueue.c:1655
queue_delayed_work_on+0xd1/0xe0 kernel/workqueue.c:1680
psi_task_change+0x142/0x220 kernel/sched/psi.c:807
psi_enqueue kernel/sched/stats.h:82 [inline]
enqueue_task kernel/sched/core.c:1592 [inline]
activate_task kernel/sched/core.c:1615 [inline]
wake_up_new_task+0x9f2/0xdd0 kernel/sched/core.c:3834
kernel_clone+0x1f0/0xab0 kernel/fork.c:2489
kernel_thread+0xb5/0xf0 kernel/fork.c:2517
rest_init+0x23/0x388 init/main.c:687
start_kernel+0x470/0x491 init/main.c:1064
secondary_startup_64_no_verify+0xb0/0xbb

-> #2 (&rq->lock){-.-.}-{2:2}:
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
rq_lock kernel/sched/sched.h:1318 [inline]
task_fork_fair+0x74/0x4d0 kernel/sched/fair.c:10767
sched_fork+0x3fc/0xbd0 kernel/sched/core.c:3764
copy_process+0x1d61/0x6fc0 kernel/fork.c:2070
kernel_clone+0xe7/0xab0 kernel/fork.c:2465
kernel_thread+0xb5/0xf0 kernel/fork.c:2517
rest_init+0x23/0x388 init/main.c:687
start_kernel+0x470/0x491 init/main.c:1064
secondary_startup_64_no_verify+0xb0/0xbb

-> #1 (&p->pi_lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
try_to_wake_up+0x98/0x13b0 kernel/sched/core.c:3335
autoremove_wake_function+0x12/0x140 kernel/sched/wait.c:404
__wake_up_common+0x147/0x650 kernel/sched/wait.c:108
__wake_up_common_lock+0xd0/0x130 kernel/sched/wait.c:138
__kfence_alloc+0xa0/0xbc0 mm/kfence/core.c:710
kfence_alloc include/linux/kfence.h:108 [inline]
slab_alloc_node mm/slub.c:2826 [inline]
kmem_cache_alloc_node_trace+0x28d/0x3d0 mm/slub.c:2953
kmalloc_node include/linux/slab.h:570 [inline]
kzalloc_node include/linux/slab.h:693 [inline]
alloc_worker kernel/workqueue.c:1826 [inline]
create_worker+0xfe/0x6d0 kernel/workqueue.c:1923
maybe_create_worker kernel/workqueue.c:2094 [inline]
manage_workers kernel/workqueue.c:2146 [inline]
worker_thread+0xaef/0x1120 kernel/workqueue.c:2393
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

-> #0 (allocation_wait.lock){..-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:2868 [inline]
check_prevs_add kernel/locking/lockdep.c:2993 [inline]
validate_chain kernel/locking/lockdep.c:3608 [inline]
__lock_acquire+0x2ade/0x5500 kernel/locking/lockdep.c:4832
lock_acquire kernel/locking/lockdep.c:5437 [inline]
lock_acquire+0x29d/0x740 kernel/locking/lockdep.c:5402
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
__wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137
__kfence_alloc+0xa0/0xbc0 mm/kfence/core.c:710
kfence_alloc include/linux/kfence.h:108 [inline]
slab_alloc_node mm/slub.c:2826 [inline]
slab_alloc mm/slub.c:2911 [inline]
kmem_cache_alloc+0x259/0x470 mm/slub.c:2916
kmem_cache_zalloc include/linux/slab.h:672 [inline]
fill_pool+0x264/0x5c0 lib/debugobjects.c:171
__debug_object_init+0x7a/0xd10 lib/debugobjects.c:560
debug_object_init lib/debugobjects.c:615 [inline]
debug_object_activate+0x32c/0x3e0 lib/debugobjects.c:701
debug_timer_activate kernel/time/timer.c:727 [inline]
__mod_timer+0x77d/0xe30 kernel/time/timer.c:1048
__queue_delayed_work+0x1a7/0x270 kernel/workqueue.c:1655
queue_delayed_work_on+0xd1/0xe0 kernel/workqueue.c:1680
queue_delayed_work include/linux/workqueue.h:522 [inline]
schedule_delayed_work include/linux/workqueue.h:626 [inline]
unaccount_event kernel/events/core.c:4703 [inline]
_free_event+0xf49/0x1300 kernel/events/core.c:4812
put_event kernel/events/core.c:4935 [inline]
perf_event_release_kernel+0xa24/0xe00 kernel/events/core.c:5050
perf_release+0x33/0x40 kernel/events/core.c:5060
__fput+0x283/0x920 fs/file_table.c:280
task_work_run+0xdd/0x190 kernel/task_work.c:140
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
entry_SYSCALL_64_after_hwframe+0x44/0xa9

other info that might help us debug this:

Chain exists of:
allocation_wait.lock --> &rq->lock --> &base->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&base->lock);
lock(&rq->lock);
lock(&base->lock);
lock(allocation_wait.lock);

*** DEADLOCK ***

1 lock held by syz-executor.0/9817:
#0: ffff8880b9e24898 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x5a/0x1f0 kernel/time/timer.c:944

stack backtrace:
CPU: 0 PID: 9817 Comm: syz-executor.0 Not tainted 5.10.0-next-20201223-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:120
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2117
check_prev_add kernel/locking/lockdep.c:2868 [inline]
check_prevs_add kernel/locking/lockdep.c:2993 [inline]
validate_chain kernel/locking/lockdep.c:3608 [inline]
__lock_acquire+0x2ade/0x5500 kernel/locking/lockdep.c:4832
lock_acquire kernel/locking/lockdep.c:5437 [inline]
lock_acquire+0x29d/0x740 kernel/locking/lockdep.c:5402
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
__wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137
__kfence_alloc+0xa0/0xbc0 mm/kfence/core.c:710
kfence_alloc include/linux/kfence.h:108 [inline]
slab_alloc_node mm/slub.c:2826 [inline]
slab_alloc mm/slub.c:2911 [inline]
kmem_cache_alloc+0x259/0x470 mm/slub.c:2916
kmem_cache_zalloc include/linux/slab.h:672 [inline]
fill_pool+0x264/0x5c0 lib/debugobjects.c:171
__debug_object_init+0x7a/0xd10 lib/debugobjects.c:560
debug_object_init lib/debugobjects.c:615 [inline]
debug_object_activate+0x32c/0x3e0 lib/debugobjects.c:701
debug_timer_activate kernel/time/timer.c:727 [inline]
__mod_timer+0x77d/0xe30 kernel/time/timer.c:1048
__queue_delayed_work+0x1a7/0x270 kernel/workqueue.c:1655
queue_delayed_work_on+0xd1/0xe0 kernel/workqueue.c:1680
queue_delayed_work include/linux/workqueue.h:522 [inline]
schedule_delayed_work include/linux/workqueue.h:626 [inline]
unaccount_event kernel/events/core.c:4703 [inline]
_free_event+0xf49/0x1300 kernel/events/core.c:4812
put_event kernel/events/core.c:4935 [inline]
perf_event_release_kernel+0xa24/0xe00 kernel/events/core.c:5050
perf_release+0x33/0x40 kernel/events/core.c:5060
__fput+0x283/0x920 fs/file_table.c:280
task_work_run+0xdd/0x190 kernel/task_work.c:140
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x417bf1
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 a4 1a 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffe977a18a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000417bf1
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000003
RBP: 0000000000000001 R08: 0000000000000ab3 R09: 00000000e0282ab7
R10: 00007ffe977a1980 R11: 0000000000000293 R12: 000000000119ca00
R13: 000000000119ca00 R14: 00000000000003e8 R15: 000000000119bf8c


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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