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SubjectWARNING in enqueue_task_dl
From
Hello,

syzbot found the following crash on:

HEAD commit: 1ce80e0fe98e Merge tag 'fsnotify_for_v4.20-rc3' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ddbb0b400000
kernel config: https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
dashboard link: https://syzkaller.appspot.com/bug?extid=119ba87189432ead09b4
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13e9e015400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
hrtimer: interrupt took 33411 ns
sched: DL replenish lagged too much
WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628
enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
PM: Basic memory bitmaps freed
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 6351 Comm: syz-executor0 Not tainted 4.20.0-rc2+ #338
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
panic+0x2ad/0x55c kernel/panic.c:188
__warn.cold.8+0x20/0x45 kernel/panic.c:540
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
RIP: 0010:enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
Code: ff 48 8b 8d c8 fe ff ff 48 c1 e6 2a 4c 8b 9d d0 fe ff ff 8b 95 d8 fe
ff ff 48 8b 85 e0 fe ff ff e9 16 e4 ff ff e8 16 d0 ea ff <0f> 0b e9 17 f1
ff ff 48 8b bd e8 fe ff ff 4c 89 95 c8 fe ff ff 48
RSP: 0018:ffff8881ba39fa18 EFLAGS: 00010002
RAX: 0000000000000000 RBX: ffff8881b9d6c000 RCX: ffff8881b9d6c278
RDX: ffff8881b9d6c03c RSI: 0000000000000002 RDI: ffff8881daf2d710
RBP: ffff8881ba39fb78 R08: 0000000000000001 R09: ffff8881daf00000
R10: 0000001a4d4f1987 R11: ffff8881daf2db3b R12: 1ffff11037473f4e
R13: ffff8881b9d6c2cc R14: ffff8881daf2ccc0 R15: ffff8881daf2ccc0
enqueue_task+0x184/0x390 kernel/sched/core.c:730
__sched_setscheduler+0xe99/0x2190 kernel/sched/core.c:4336
sched_setattr kernel/sched/core.c:4394 [inline]
__do_sys_sched_setattr kernel/sched/core.c:4570 [inline]
__se_sys_sched_setattr kernel/sched/core.c:4549 [inline]
__x64_sys_sched_setattr+0x1b2/0x2f0 kernel/sched/core.c:4549
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f05ce0a2c78 EFLAGS: 00000246 ORIG_RAX: 000000000000013a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f05ce0a36d4
R13: 00000000004c369f R14: 00000000004d5730 R15: 00000000ffffffff

======================================================
WARNING: possible circular locking dependency detected
4.20.0-rc2+ #338 Not tainted
------------------------------------------------------
syz-executor0/6351 is trying to acquire lock:
00000000b2b97155 ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70
kernel/locking/semaphore.c:136

but task is already holding lock:
000000004cd5557e (&rq->lock){-.-.}, at: task_rq_lock+0xc5/0x2a0
kernel/sched/core.c:99

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&rq->lock){-.-.}:
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
rq_lock kernel/sched/sched.h:1126 [inline]
task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:9768
sched_fork+0x443/0xba0 kernel/sched/core.c:2359
copy_process+0x25b8/0x87a0 kernel/fork.c:1887
_do_fork+0x1cb/0x11d0 kernel/fork.c:2216
kernel_thread+0x34/0x40 kernel/fork.c:2275
rest_init+0x28/0x372 init/main.c:409
arch_call_rest_init+0xe/0x1b
start_kernel+0x9f0/0xa2b init/main.c:745
x86_64_start_reservations+0x2e/0x30 arch/x86/kernel/head64.c:472
x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #1 (&p->pi_lock){-.-.}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
try_to_wake_up+0xdc/0x1490 kernel/sched/core.c:1965
wake_up_process+0x10/0x20 kernel/sched/core.c:2129
__up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262
up+0x13c/0x1c0 kernel/locking/semaphore.c:187
__up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:236
console_unlock+0x811/0x1190 kernel/printk/printk.c:2432
do_con_write+0x1356/0x23b0 drivers/tty/vt/vt.c:2767
con_write+0x25/0xc0 drivers/tty/vt/vt.c:3116
process_output_block drivers/tty/n_tty.c:593 [inline]
n_tty_write+0x6c1/0x11a0 drivers/tty/n_tty.c:2331
do_tty_write drivers/tty/tty_io.c:959 [inline]
tty_write+0x3f1/0x880 drivers/tty/tty_io.c:1043
__vfs_write+0x119/0x9f0 fs/read_write.c:485
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 ((console_sem).lock){-.-.}:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
__down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
console_trylock_spinning kernel/printk/printk.c:1653 [inline]
vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
printk+0xa7/0xcf kernel/printk/printk.c:1997
__warn+0x9e/0x1d0 kernel/panic.c:522
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
enqueue_task+0x184/0x390 kernel/sched/core.c:730
__sched_setscheduler+0xe99/0x2190 kernel/sched/core.c:4336
sched_setattr kernel/sched/core.c:4394 [inline]
__do_sys_sched_setattr kernel/sched/core.c:4570 [inline]
__se_sys_sched_setattr kernel/sched/core.c:4549 [inline]
__x64_sys_sched_setattr+0x1b2/0x2f0 kernel/sched/core.c:4549
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

Chain exists of:
(console_sem).lock --> &p->pi_lock --> &rq->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&rq->lock);
lock(&p->pi_lock);
lock(&rq->lock);
lock((console_sem).lock);

*** DEADLOCK ***

3 locks held by syz-executor0/6351:
#0: 000000001a0356c1 (rcu_read_lock){....}, at: __do_sys_sched_setattr
kernel/sched/core.c:4563 [inline]
#0: 000000001a0356c1 (rcu_read_lock){....}, at: __se_sys_sched_setattr
kernel/sched/core.c:4549 [inline]
#0: 000000001a0356c1 (rcu_read_lock){....}, at:
__x64_sys_sched_setattr+0x146/0x2f0 kernel/sched/core.c:4549
#1: 000000000b71b478 (&p->pi_lock){-.-.}, at: task_rq_lock+0x62/0x2a0
kernel/sched/core.c:97
#2: 000000004cd5557e (&rq->lock){-.-.}, at: task_rq_lock+0xc5/0x2a0
kernel/sched/core.c:99

stack backtrace:
CPU: 1 PID: 6351 Comm: syz-executor0 Not tainted 4.20.0-rc2+ #338
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
print_circular_bug.isra.35.cold.54+0x1bd/0x27d
kernel/locking/lockdep.c:1221
check_prev_add kernel/locking/lockdep.c:1863 [inline]
check_prevs_add kernel/locking/lockdep.c:1976 [inline]
validate_chain kernel/locking/lockdep.c:2347 [inline]
__lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3341
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
__down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
console_trylock_spinning kernel/printk/printk.c:1653 [inline]
vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
printk+0xa7/0xcf kernel/printk/printk.c:1997
__warn+0x9e/0x1d0 kernel/panic.c:522
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
RIP: 0010:enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504
Code: ff 48 8b 8d c8 fe ff ff 48 c1 e6 2a 4c 8b 9d d0 fe ff ff 8b 95 d8 fe
ff ff 48 8b 85 e0 fe ff ff e9 16 e4 ff ff e8 16 d0 ea ff <0f> 0b e9 17 f1
ff ff 48 8b bd e8 fe ff ff 4c 89 95 c8 fe ff ff 48
RSP: 0018:ffff8881ba39fa18 EFLAGS: 00010002
RAX: 0000000000000000 RBX: ffff8881b9d6c000 RCX: ffff8881b9d6c278
RDX: ffff8881b9d6c03c RSI: 0000000000000002 RDI: ffff8881daf2d710
RBP: ffff8881ba39fb78 R08: 0000000000000001 R09: ffff8881daf00000
R10: 0000001a4d4f1987 R11: ffff8881daf2db3b R12: 1ffff11037473f4e
R13: ffff8881b9d6c2cc R14: ffff8881daf2ccc0 R15: ffff8881daf2ccc0
enqueue_task+0x184/0x390 kernel/sched/core.c:730
__sched_setscheduler+0xe99/0x2190 kernel/sched/core.c:4336
sched_setattr kernel/sched/core.c:4394 [inline]
__do_sys_sched_setattr kernel/sched/core.c:4570 [inline]
__se_sys_sched_setattr kernel/sched/core.c:4549 [inline]
__x64_sys_sched_setattr+0x1b2/0x2f0 kernel/sched/core.c:4549
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f05ce0a2c78 EFLAGS: 00000246 ORIG_RAX: 000000000000013a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f05ce0a36d4
R13: 00000000004c369f R14: 00000000004d5730 R15: 00000000ffffffff
Shutting down cpus with NMI
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug 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 bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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