Re: [BUG] possible deadlock in __rcu_irq_enter_check_tick

From: Yu Liao
Date: Mon Oct 17 2022 - 22:34:03 EST

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In reply to: Zhang, Qiang1: "RE: [BUG] possible deadlock in __rcu_irq_enter_check_tick"
Next in thread: Mark Rutland: "Re: [BUG] possible deadlock in __rcu_irq_enter_check_tick"
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On 2022/10/17 17:32, Zhang, Qiang1 wrote:
> On Tue, Oct 11, 2022 at 09:18:11PM +0800, Yu Liao wrote:
>> Hello,
>>
>> When I run syzkaller, a deadlock problem occurs. The call stack is as follows:
>> [ 1088.244366][ C1] ======================================================
>> [ 1088.244838][ C1] WARNING: possible circular locking dependency detected
>> [ 1088.245313][ C1] 5.10.0-04424-ga472e3c833d3 #1 Not tainted
>> [ 1088.245745][ C1] ------------------------------------------------------
>>
>> It is quite possible that an unfortunate set of commits were backported
>> to v5.10. Could you please bisect?
>>
>
> Hi Yu liao
>
> This looks like the result of the following commit:
>
> commit 2a9b3e6ac69a8bf177d8496a11e749e2dc72fa22
> Author: Mark Rutland <mark.rutland@xxxxxxx>
> Date: Mon Nov 30 11:59:50 2020 +0000
>
> arm64: entry: fix EL1 debug transitions
>
>
> Is it possible to try the following modification? maybe Mark have better solution.
>
Thanks for the reply, this problem was reported by syzkaller, and I have not
been able to reproduce it yet. But this modification seems to work, when
called from arm64_enter_el1_dbg it prevents rcu_nmi_enter from calling
rcu_irq_enter_check_tick which may holds the rcu_node lock.

Thanks
Yu Liao
> --- a/arch/arm64/kernel/entry-common.c
> +++ b/arch/arm64/kernel/entry-common.c
> @@ -259,7 +259,7 @@ static void noinstr el1_inv(struct pt_regs *regs, unsigned long esr)
> static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs)
> {
> regs->lockdep_hardirqs = lockdep_hardirqs_enabled();
> -
> + __nmi_enter();
> lockdep_hardirqs_off(CALLER_ADDR0);
> rcu_nmi_enter();
>
> @@ -278,6 +278,7 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
> rcu_nmi_exit();
> if (restore)
> lockdep_hardirqs_on(CALLER_ADDR0);
> + __nmi_exit();
> }
>
> Thanks
> Zqiang
>
>
>> [ 1088.246214][ C1] syz-executor.2/932 is trying to acquire lock:
>> [ 1088.246628][ C1] ffffa0001440c418 (rcu_node_0){..-.}-{2:2}, at:
>> __rcu_irq_enter_check_tick+0x128/0x2f4
>> [ 1088.247330][ C1]
>> [ 1088.247330][ C1] but task is already holding lock:
>> [ 1088.247830][ C1] ffff000224d0c298 (&rq->lock){-.-.}-{2:2}, at:
>> try_to_wake_up+0x6e0/0xd40
>> [ 1088.248424][ C1]
>> [ 1088.248424][ C1] which lock already depends on the new lock.
>> [ 1088.248424][ C1]
>> [ 1088.249127][ C1]
>> [ 1088.249127][ C1] the existing dependency chain (in reverse order) is:
>> [ 1088.249726][ C1]
>> [ 1088.249726][ C1] -> #1 (&rq->lock){-.-.}-{2:2}:
>> [ 1088.250239][ C1] validate_chain+0x6dc/0xb0c
>> [ 1088.250591][ C1] __lock_acquire+0x498/0x940
>> [ 1088.250942][ C1] lock_acquire+0x228/0x580
>> [ 1088.251346][ C1] _raw_spin_lock_irqsave+0xc0/0x15c
>> [ 1088.251758][ C1] resched_cpu+0x5c/0x110
>> [ 1088.252091][ C1] rcu_implicit_dynticks_qs+0x2b0/0x5d0
>> [ 1088.252501][ C1] force_qs_rnp+0x244/0x39c
>> [ 1088.252847][ C1] rcu_gp_fqs_loop+0x2e4/0x440
>> [ 1088.253219][ C1] rcu_gp_kthread+0x1a4/0x240
>> [ 1088.253597][ C1] kthread+0x20c/0x260
>> [ 1088.253963][ C1] ret_from_fork+0x10/0x18
>> [ 1088.254389][ C1]
>> [ 1088.254389][ C1] -> #0 (rcu_node_0){..-.}-{2:2}:
>> [ 1088.255296][ C1] check_prev_add+0xe0/0x105c
>> [ 1088.256000][ C1] check_prevs_add+0x1c8/0x3d4
>> [ 1088.256693][ C1] validate_chain+0x6dc/0xb0c
>> [ 1088.257372][ C1] __lock_acquire+0x498/0x940
>> [ 1088.257731][ C1] lock_acquire+0x228/0x580
>> [ 1088.258079][ C1] _raw_spin_lock+0xa0/0x120
>> [ 1088.258425][ C1] __rcu_irq_enter_check_tick+0x128/0x2f4
>> [ 1088.258844][ C1] rcu_nmi_enter+0xc4/0xd0
>>
>> This is looking like we took an interrupt while holding an rq lock.
>> Am I reading this correctly? If so, that is bad in and of itself.
>>
>> Thanx, Paul
>>
>> [ 1088.259183][ C1] arm64_enter_el1_dbg+0xb0/0x160
>> [ 1088.259623][ C1] el1_dbg+0x28/0x50
>> [ 1088.260011][ C1] el1_sync_handler+0xf4/0x150
>> [ 1088.260481][ C1] el1_sync+0x74/0x100
>> [ 1088.260800][ C1] update_irq_load_avg+0x5d8/0xaa0
>> [ 1088.261194][ C1] update_rq_clock_task+0xb8/0x2d0
>> [ 1088.261595][ C1] update_rq_clock+0x8c/0x120
>> [ 1088.261952][ C1] try_to_wake_up+0x70c/0xd40
>> [ 1088.262305][ C1] wake_up_process+0x1c/0x24
>> [ 1088.262652][ C1] wakeup_softirqd+0x58/0x64
>> [ 1088.263000][ C1] __do_softirq+0x6b8/0x95c
>> [ 1088.263345][ C1] irq_exit+0x27c/0x2d0
>> [ 1088.263674][ C1] __handle_domain_irq+0x100/0x184
>> [ 1088.264049][ C1] gic_handle_irq+0xc0/0x760
>> [ 1088.264394][ C1] el1_irq+0xb8/0x140
>> [ 1088.264709][ C1] _raw_spin_unlock_irqrestore+0x7c/0x130
>> [ 1088.265134][ C1] __aarch64_insn_write+0xc4/0x100
>> [ 1088.265516][ C1] aarch64_insn_patch_text_nosync+0x40/0xa0
>> [ 1088.265942][ C1] ftrace_make_nop+0x120/0x1a4
>> [ 1088.266300][ C1] __ftrace_replace_code+0xdc/0x160
>> [ 1088.266684][ C1] ftrace_replace_code+0x100/0x1a4
>> [ 1088.267063][ C1] ftrace_modify_all_code+0x1a8/0x260
>> [ 1088.267456][ C1] arch_ftrace_update_code+0x1c/0x2c
>> [ 1088.267847][ C1] ftrace_run_update_code+0x38/0xa4
>> [ 1088.268259][ C1] ftrace_shutdown.part.0+0x2dc/0x550
>> [ 1088.268682][ C1] unregister_ftrace_function+0x74/0xc0
>> [ 1088.269117][ C1] perf_ftrace_event_register+0x130/0x1a0
>> [ 1088.269559][ C1] perf_trace_destroy+0x68/0x9c
>> [ 1088.269938][ C1] tp_perf_event_destroy+0x1c/0x2c
>> [ 1088.270340][ C1] _free_event+0x2f4/0x670
>> [ 1088.270696][ C1] put_event+0x7c/0x90
>> [ 1088.271031][ C1] perf_event_release_kernel+0x3c0/0x450
>> [ 1088.271467][ C1] perf_release+0x24/0x34
>> [ 1088.271824][ C1] __fput+0x1dc/0x500
>> [ 1088.272155][ C1] ____fput+0x24/0x30
>> [ 1088.272471][ C1] task_work_run+0xf4/0x1ec
>> [ 1088.272811][ C1] do_notify_resume+0x378/0x410
>> [ 1088.273180][ C1] work_pending+0xc/0x198
>> [ 1088.273504][ C1]
>> [ 1088.273504][ C1] other info that might help us debug this:
>> [ 1088.273504][ C1]
>> [ 1088.274168][ C1] Possible unsafe locking scenario:
>> [ 1088.274168][ C1]
>> [ 1088.274658][ C1] CPU0 CPU1
>> [ 1088.275012][ C1] ---- ----
>> [ 1088.275367][ C1] lock(&rq->lock);
>> [ 1088.275646][ C1] lock(rcu_node_0);
>> [ 1088.276082][ C1] lock(&rq->lock);
>> [ 1088.276517][ C1] lock(rcu_node_0);
>> [ 1088.276797][ C1]
>> [ 1088.276797][ C1] *** DEADLOCK ***
>> [ 1088.276797][ C1]
>> [ 1088.277339][ C1] 4 locks held by syz-executor.2/932:
>> [ 1088.277696][ C1] #0: ffffa000145251e8 (event_mutex){+.+.}-{3:3}, at:
>> perf_trace_destroy+0x34/0x9c
>> [ 1088.278345][ C1] #1: ffffa000144fb5a8 (ftrace_lock){+.+.}-{3:3}, at:
>> unregister_ftrace_function+0x2c/0xc0
>> [ 1088.279034][ C1] #2: ffff0000c0e0c968 (&p->pi_lock){-.-.}-{2:2}, at:
>> try_to_wake_up+0xbc/0xd40
>> [ 1088.279672][ C1] #3: ffff000224d0c298 (&rq->lock){-.-.}-{2:2}, at:
>> try_to_wake_up+0x6e0/0xd40
>> [ 1088.280300][ C1]
>> [ 1088.280300][ C1] stack backtrace:
>> [ 1088.280706][ C1] CPU: 1 PID: 932 Comm: syz-executor.2 Not tainted
>> 5.10.0-04424-ga472e3c833d3 #1
>> [ 1088.281315][ C1] Hardware name: linux,dummy-virt (DT)
>> [ 1088.281679][ C1] Call trace:
>> [ 1088.281910][ C1] dump_backtrace+0x0/0x41c
>> [ 1088.282218][ C1] show_stack+0x30/0x40
>> [ 1088.282505][ C1] dump_stack+0x1fc/0x2c0
>> [ 1088.282807][ C1] print_circular_bug+0x1ec/0x284
>> [ 1088.283149][ C1] check_noncircular+0x1cc/0x1ec
>> [ 1088.283486][ C1] check_prev_add+0xe0/0x105c
>> [ 1088.283804][ C1] check_prevs_add+0x1c8/0x3d4
>> [ 1088.284126][ C1] validate_chain+0x6dc/0xb0c
>> [ 1088.284442][ C1] __lock_acquire+0x498/0x940
>> [ 1088.284764][ C1] lock_acquire+0x228/0x580
>> [ 1088.285072][ C1] _raw_spin_lock+0xa0/0x120
>> [ 1088.285392][ C1] __rcu_irq_enter_check_tick+0x128/0x2f4
>> [ 1088.285779][ C1] rcu_nmi_enter+0xc4/0xd0
>> [ 1088.286082][ C1] arm64_enter_el1_dbg+0xb0/0x160
>> [ 1088.286420][ C1] el1_dbg+0x28/0x50
>> [ 1088.286689][ C1] el1_sync_handler+0xf4/0x150
>> [ 1088.287010][ C1] el1_sync+0x74/0x100
>> [ 1088.287295][ C1] update_irq_load_avg+0x5d8/0xaa0
>> [ 1088.287640][ C1] update_rq_clock_task+0xb8/0x2d0
>> [ 1088.287988][ C1] update_rq_clock+0x8c/0x120
>> [ 1088.288309][ C1] try_to_wake_up+0x70c/0xd40
>> [ 1088.288629][ C1] wake_up_process+0x1c/0x24
>> [ 1088.288945][ C1] wakeup_softirqd+0x58/0x64
>> [ 1088.289271][ C1] __do_softirq+0x6b8/0x95c
>> [ 1088.289580][ C1] irq_exit+0x27c/0x2d0
>> [ 1088.289868][ C1] __handle_domain_irq+0x100/0x184
>> [ 1088.290211][ C1] gic_handle_irq+0xc0/0x760
>> [ 1088.290522][ C1] el1_irq+0xb8/0x140
>> [ 1088.290801][ C1] _raw_spin_unlock_irqrestore+0x7c/0x130
>> [ 1088.291188][ C1] __aarch64_insn_write+0xc4/0x100
>> [ 1088.291533][ C1] aarch64_insn_patch_text_nosync+0x40/0xa0
>> [ 1088.291928][ C1] ftrace_make_nop+0x120/0x1a4
>> [ 1088.292256][ C1] __ftrace_replace_code+0xdc/0x160
>> [ 1088.292613][ C1] ftrace_replace_code+0x100/0x1a4
>> [ 1088.292963][ C1] ftrace_modify_all_code+0x1a8/0x260
>> [ 1088.293335][ C1] arch_ftrace_update_code+0x1c/0x2c
>> [ 1088.293694][ C1] ftrace_run_update_code+0x38/0xa4
>> [ 1088.294048][ C1] ftrace_shutdown.part.0+0x2dc/0x550
>> [ 1088.294415][ C1] unregister_ftrace_function+0x74/0xc0
>> [ 1088.294787][ C1] perf_ftrace_event_register+0x130/0x1a0
>> [ 1088.295172][ C1] perf_trace_destroy+0x68/0x9c
>> [ 1088.295500][ C1] tp_perf_event_destroy+0x1c/0x2c
>> [ 1088.295850][ C1] _free_event+0x2f4/0x670
>> [ 1088.296154][ C1] put_event+0x7c/0x90
>> [ 1088.296439][ C1] perf_event_release_kernel+0x3c0/0x450
>> [ 1088.296820][ C1] perf_release+0x24/0x34
>> [ 1088.297125][ C1] __fput+0x1dc/0x500
>> [ 1088.297404][ C1] ____fput+0x24/0x30
>> [ 1088.297682][ C1] task_work_run+0xf4/0x1ec
>> [ 1088.297989][ C1] do_notify_resume+0x378/0x410
>> [ 1088.298316][ C1] work_pending+0xc/0x198
>>

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