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SubjectRe: WARNING in enqueue_task_dl
Hi all,

On Mon, 19 Nov 2018 09:23:03 +0100 (CET)
Thomas Gleixner <tglx@linutronix.de> wrote:

> Adding scheduler folks
>
> On Sun, 18 Nov 2018, syzbot wrote:
>
> > 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

Here, it looks like a task is invoking sched_setattr() to become
SCHED_DEADLINE when dl_boosted is set...

Is this possible / correct?

If this (sched_setattr() with dl_boosted set) should not be possible,
then we have a bug that we need to investigate...

Otherwise, I suspect we can just remove the WARN_ON at line 628 of
deadline.c


Luca




> > 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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