On Mon, 27 May 2019, Paul E. McKenney wrote:
> The TASKS03 and TREE04 rcutorture scenarios produce the following
> lockdep complaint:
>
> ================================
> WARNING: inconsistent lock state
> 5.2.0-rc1+ #513 Not tainted
> --------------------------------
> inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
> migration/1/14 [HC0[0]:SC0[0]:HE1:SE1] takes:
> (____ptrval____) (tick_broadcast_lock){?...}, at:
> tick_broadcast_offline+0xf/0x70
> {IN-HARDIRQ-W} state was registered at:
> lock_acquire+0xb0/0x1c0
> _raw_spin_lock_irqsave+0x3c/0x50
> tick_broadcast_switch_to_oneshot+0xd/0x40
> tick_switch_to_oneshot+0x4f/0xd0
> hrtimer_run_queues+0xf3/0x130
> run_local_timers+0x1c/0x50
> update_process_times+0x1c/0x50
> tick_periodic+0x26/0xc0
> tick_handle_periodic+0x1a/0x60
> smp_apic_timer_interrupt+0x80/0x2a0
> apic_timer_interrupt+0xf/0x20
> _raw_spin_unlock_irqrestore+0x4e/0x60
> rcu_nocb_gp_kthread+0x15d/0x590
> kthread+0xf3/0x130
> ret_from_fork+0x3a/0x50
> irq event stamp: 171
> hardirqs last enabled at (171): [<ffffffff8a201a37>]
> trace_hardirqs_on_thunk+0x1a/0x1c
> hardirqs last disabled at (170): [<ffffffff8a201a53>]
> trace_hardirqs_off_thunk+0x1a/0x1c
> softirqs last enabled at (0): [<ffffffff8a264ee0>]
> copy_process.part.56+0x650/0x1cb0
> softirqs last disabled at (0): [<0000000000000000>] 0x0
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(tick_broadcast_lock);
> <Interrupt>
> lock(tick_broadcast_lock);
>
> *** DEADLOCK ***
>
> 1 lock held by migration/1/14:
> #0: (____ptrval____) (clockevents_lock){+.+.}, at: tick_offline_cpu+0xf/0x30
>
> stack backtrace:
> CPU: 1 PID: 14 Comm: migration/1 Not tainted 5.2.0-rc1+ #513
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Bochs 01/01/2011
> Call Trace:
> dump_stack+0x5e/0x8b
> print_usage_bug+0x1fc/0x216
> ? print_shortest_lock_dependencies+0x1b0/0x1b0
> mark_lock+0x1f2/0x280
> __lock_acquire+0x1e0/0x18f0
> ? __lock_acquire+0x21b/0x18f0
> ? _raw_spin_unlock_irqrestore+0x4e/0x60
> lock_acquire+0xb0/0x1c0
> ? tick_broadcast_offline+0xf/0x70
> _raw_spin_lock+0x33/0x40
> ? tick_broadcast_offline+0xf/0x70
> tick_broadcast_offline+0xf/0x70
> tick_offline_cpu+0x16/0x30
> take_cpu_down+0x7d/0xa0
> multi_cpu_stop+0xa2/0xe0
> ? cpu_stop_queue_work+0xc0/0xc0
> cpu_stopper_thread+0x6d/0x100
> smpboot_thread_fn+0x169/0x240
> kthread+0xf3/0x130
> ? sort_range+0x20/0x20
> ? kthread_cancel_delayed_work_sync+0x10/0x10
> ret_from_fork+0x3a/0x50
>
> It turns out that tick_broadcast_offline() can be invoked with interrupts
> enabled, so this commit fixes this issue by replacing the raw_spin_lock()
> with raw_spin_lock_irqsave().
What?
take_cpu_down() is called from multi_cpu_stop() with interrupts disabled.
So this is just papering over the fact that something called from
take_cpu_down() enabled interrupts. That needs to be found and fixed.
Thanks,
tglx
