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Message-ID: <20150430162945.GH3488@pd.tnic>
Date: Thu, 30 Apr 2015 18:29:45 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ethan Zhao <ethan.zhao@...cle.com>
Cc: tony.luck@...el.com, tglx@...utronix.de, mingo@...hat.com,
hpa@...or.com, x86@...nel.org, linux-edac@...r.kernel.org,
linux-kernel@...r.kernel.org, ethan.kernel@...il.com,
tim.uglow@...cle.com
Subject: Re: [PATCH] x86/mce: fix mce_restart() race with CPU hotplug
operation
On Thu, Apr 30, 2015 at 12:04:53AM +0900, Ethan Zhao wrote:
> while testing CPU hotplug and MCE with following two scripts,
>
> script 1:
>
> for i in {1..30}; do while :; do ((a=$RANDOM%160)); echo 0 >>
> /sys/devices/system/cpu/cpu${i}/online; echo 1 >>
> /sys/devices/system/cpu/cpu${i}/online; done & done
>
> script 2:
>
> while :; do for i in $(ls
> /sys/devices/system/machinecheck/machinecheck*/check_interval); do echo 1 >>
> $i; done; done
For the record, it is a public secret that CPU hotplug is broken. IOW,
you're wasting your time with those senseless pounder tests but ok.
...
> ---
> arch/x86/kernel/cpu/mcheck/mce.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 3c036cb..fcc2794 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -1338,8 +1338,10 @@ static void mce_timer_delete_all(void)
> {
> int cpu;
>
> + get_online_cpus();
> for_each_online_cpu(cpu)
> del_timer_sync(&per_cpu(mce_timer, cpu));
> + put_online_cpus();
> }
>
> static void mce_do_trigger(struct work_struct *work)
> @@ -2085,7 +2087,9 @@ static void mce_cpu_restart(void *data)
> static void mce_restart(void)
> {
> mce_timer_delete_all();
> + get_online_cpus();
> on_each_cpu(mce_cpu_restart, NULL, 1);
> + put_online_cpus();
With your patch applied I get on 4.1-rc1+:
---
[ 41.364909] kvm: disabling virtualization on CPU1
[ 41.371083] smpboot: CPU 1 is now offline
[ 41.381190] x86: Booting SMP configuration:
[ 41.385405] smpboot: Booting Node 0 Processor 1 APIC 0x2
[ 41.402901] kvm: enabling virtualization on CPU1
[ 41.440944] kvm: disabling virtualization on CPU1
[ 41.447010] smpboot: CPU 1 is now offline
[ 41.486082] kvm: disabling virtualization on CPU6
[ 41.491827] smpboot: CPU 6 is now offline
[ 41.497521] smpboot: Booting Node 0 Processor 6 APIC 0x5
[ 41.514983] kvm: enabling virtualization on CPU6
[ 41.561643] kvm: disabling virtualization on CPU6
[ 41.566848] smpboot: CPU 6 is now offline
[ 41.572606] smpboot: Booting Node 0 Processor 6 APIC 0x5
[ 41.590049] kvm: enabling virtualization on CPU6
[ 41.636817] kvm: disabling virtualization on CPU6
[ 41.642575] smpboot: CPU 6 is now offline
[ 41.676812] kvm: disabling virtualization on CPU7
[ 41.682429] smpboot: CPU 7 is now offline
[ 41.687974] smpboot: Booting Node 0 Processor 7 APIC 0x7
[ 41.705416] kvm: enabling virtualization on CPU7
[ 41.752739] kvm: disabling virtualization on CPU7
[ 41.758455] smpboot: CPU 7 is now offline
[ 41.764089] smpboot: Booting Node 0 Processor 7 APIC 0x7
[ 41.781561] kvm: enabling virtualization on CPU7
[ 41.831610] kvm: disabling virtualization on CPU7
[ 41.837280] smpboot: CPU 7 is now offline
[ 41.843341] ======================================================
[ 41.849561] [ INFO: possible circular locking dependency detected ]
[ 41.855883] 4.1.0-rc1+ #2 Not tainted
[ 41.859564] -------------------------------------------------------
[ 41.865871] script2.sh/2071 is trying to acquire lock:
[ 41.871044] (cpu_hotplug.lock){++++++}, at: [<ffffffff81066c02>] get_online_cpus+0x32/0x80
[ 41.879521]
but task is already holding lock:
[ 41.885392] (s_active#121){++++.+}, at: [<ffffffff812944de>] kernfs_fop_write+0x6e/0x1a0
[ 41.893695]
which lock already depends on the new lock.
[ 41.901925]
the existing dependency chain (in reverse order) is:
[ 41.909465]
-> #2 (s_active#121){++++.+}:
[ 41.913739] [<ffffffff810c6e11>] lock_acquire+0xd1/0x2b0
[ 41.919718] [<ffffffff81292088>] __kernfs_remove+0x228/0x300
[ 41.926046] [<ffffffff81293269>] kernfs_remove_by_name_ns+0x49/0xb0
[ 41.932976] [<ffffffff81294de5>] sysfs_remove_file_ns+0x15/0x20
[ 41.939552] [<ffffffff81600939>] device_remove_file+0x19/0x20
[ 41.945968] [<ffffffff810308b4>] mce_device_remove+0x54/0xd0
[ 41.952284] [<ffffffff81030b89>] mce_cpu_callback+0x69/0x120
[ 41.958608] [<ffffffff8108fb46>] notifier_call_chain+0x66/0x90
[ 41.965124] [<ffffffff8108fb7e>] __raw_notifier_call_chain+0xe/0x10
[ 41.972053] [<ffffffff81066d33>] cpu_notify+0x23/0x50
[ 41.977761] [<ffffffff81066dfe>] cpu_notify_nofail+0xe/0x20
[ 41.983986] [<ffffffff818961d6>] _cpu_down+0x1b6/0x2d0
[ 41.989787] [<ffffffff81896326>] cpu_down+0x36/0x50
[ 41.995324] [<ffffffff816087d4>] cpu_subsys_offline+0x14/0x20
[ 42.001734] [<ffffffff816030c5>] device_offline+0x95/0xc0
[ 42.007797] [<ffffffff816031cd>] online_store+0x3d/0x90
[ 42.013673] [<ffffffff81600608>] dev_attr_store+0x18/0x30
[ 42.019735] [<ffffffff81294ca9>] sysfs_kf_write+0x49/0x60
[ 42.025796] [<ffffffff812945b0>] kernfs_fop_write+0x140/0x1a0
[ 42.032211] [<ffffffff8120d878>] __vfs_write+0x28/0xf0
[ 42.038013] [<ffffffff8120df89>] vfs_write+0xa9/0x1b0
[ 42.043715] [<ffffffff8120ed79>] SyS_write+0x49/0xb0
[ 42.049334] [<ffffffff818aacf2>] system_call_fastpath+0x16/0x7a
[ 42.055926]
-> #1 (cpu_hotplug.lock#2){+.+.+.}:
[ 42.060705] [<ffffffff810c6e11>] lock_acquire+0xd1/0x2b0
[ 42.066674] [<ffffffff818a5771>] mutex_lock_nested+0x61/0x460
[ 42.073087] [<ffffffff81066e8b>] cpu_hotplug_begin+0x7b/0xd0
[ 42.079400] [<ffffffff81066f4b>] _cpu_up+0x2b/0x160
[ 42.084927] [<ffffffff8106710a>] cpu_up+0x8a/0xb0
[ 42.090285] [<ffffffff81fac845>] smp_init+0x86/0x88
[ 42.095818] [<ffffffff81f8e113>] kernel_init_freeable+0x160/0x27d
[ 42.102577] [<ffffffff8189540e>] kernel_init+0xe/0xf0
[ 42.108455] [<ffffffff818ab162>] ret_from_fork+0x42/0x70
[ 42.114586]
-> #0 (cpu_hotplug.lock){++++++}:
[ 42.119497] [<ffffffff810c60c6>] __lock_acquire+0x1db6/0x2040
[ 42.126062] [<ffffffff810c6e11>] lock_acquire+0xd1/0x2b0
[ 42.132182] [<ffffffff81066c28>] get_online_cpus+0x58/0x80
[ 42.138476] [<ffffffff8102fc23>] mce_timer_delete_all+0x23/0x70
[ 42.145215] [<ffffffff8102fd0e>] mce_restart+0xe/0x30
[ 42.151071] [<ffffffff8102fddb>] store_int_with_restart+0x1b/0x30
[ 42.157975] [<ffffffff81600608>] dev_attr_store+0x18/0x30
[ 42.164179] [<ffffffff81294ca9>] sysfs_kf_write+0x49/0x60
[ 42.170383] [<ffffffff812945b0>] kernfs_fop_write+0x140/0x1a0
[ 42.176938] [<ffffffff8120d878>] __vfs_write+0x28/0xf0
[ 42.182879] [<ffffffff8120df89>] vfs_write+0xa9/0x1b0
[ 42.188733] [<ffffffff8120ed79>] SyS_write+0x49/0xb0
[ 42.194498] [<ffffffff818aacf2>] system_call_fastpath+0x16/0x7a
[ 42.201230]
other info that might help us debug this:
[ 42.210268] Chain exists of:
cpu_hotplug.lock --> cpu_hotplug.lock#2 --> s_active#121
[ 42.219214] Possible unsafe locking scenario:
[ 42.225875] CPU0 CPU1
[ 42.230578] ---- ----
[ 42.235283] lock(s_active#121);
[ 42.238791] lock(cpu_hotplug.lock#2);
[ 42.245362] lock(s_active#121);
[ 42.251401] lock(cpu_hotplug.lock);
[ 42.255250]
*** DEADLOCK ***
[ 42.262008] 3 locks held by script2.sh/2071:
[ 42.266446] #0: (sb_writers#6){.+.+.+}, at: [<ffffffff8120e043>] vfs_write+0x163/0x1b0
[ 42.274792] #1: (&of->mutex){+.+.+.}, at: [<ffffffff812944d6>] kernfs_fop_write+0x66/0x1a0
[ 42.283485] #2: (s_active#121){++++.+}, at: [<ffffffff812944de>] kernfs_fop_write+0x6e/0x1a0
[ 42.292353]
stack backtrace:
[ 42.297084] CPU: 3 PID: 2071 Comm: script2.sh Not tainted 4.1.0-rc1+ #2
[ 42.303880] Hardware name: Dell Inc. Precision T3600/0PTTT9, BIOS A13 05/11/2014
[ 42.311474] ffffffff82847b60 ffff88043934fb68 ffffffff818a08e0 0000000000000011
[ 42.319092] ffffffff828479b0 ffff88043934fbb8 ffffffff810c2a9d 000000000000aae0
[ 42.326712] ffff88043934fc28 0000000000000002 ffff8800a82cc0b8 0000000000000002
[ 42.334332] Call Trace:
[ 42.336939] [<ffffffff818a08e0>] dump_stack+0x4f/0x7b
[ 42.342251] [<ffffffff810c2a9d>] print_circular_bug+0x1cd/0x230
[ 42.348436] [<ffffffff810c60c6>] __lock_acquire+0x1db6/0x2040
[ 42.354455] [<ffffffff810c34d9>] ? check_irq_usage+0x89/0xc0
[ 42.360385] [<ffffffff810c6e11>] lock_acquire+0xd1/0x2b0
[ 42.365958] [<ffffffff81066c02>] ? get_online_cpus+0x32/0x80
[ 42.371880] [<ffffffff81066c28>] get_online_cpus+0x58/0x80
[ 42.377626] [<ffffffff81066c02>] ? get_online_cpus+0x32/0x80
[ 42.383556] [<ffffffff813f94ee>] ? simple_strtol+0xe/0x20
[ 42.389215] [<ffffffff8102fc23>] mce_timer_delete_all+0x23/0x70
[ 42.395401] [<ffffffff8102fd0e>] mce_restart+0xe/0x30
[ 42.400721] [<ffffffff8102fddb>] store_int_with_restart+0x1b/0x30
[ 42.407080] [<ffffffff81600608>] dev_attr_store+0x18/0x30
[ 42.412739] [<ffffffff81294ca9>] sysfs_kf_write+0x49/0x60
[ 42.418396] [<ffffffff812945b0>] kernfs_fop_write+0x140/0x1a0
[ 42.424405] [<ffffffff8120d878>] __vfs_write+0x28/0xf0
[ 42.429803] [<ffffffff8120e043>] ? vfs_write+0x163/0x1b0
[ 42.435385] [<ffffffff81188b94>] ? context_tracking_exit+0x64/0x1c0
[ 42.441922] [<ffffffff8120df89>] vfs_write+0xa9/0x1b0
[ 42.447234] [<ffffffff8120ed79>] SyS_write+0x49/0xb0
[ 42.452459] [<ffffffff818aacf2>] system_call_fastpath+0x16/0x7a
[ 42.459043] smpboot: Booting Node 0 Processor 7 APIC 0x7
[ 42.476980] kvm: enabling virtualization on CPU7
[ 42.525076] kvm: disabling virtualization on CPU7
[ 42.530297] smpboot: CPU 7 is now offline
[ 42.535071] smpboot: Booting Node 0 Processor 7 APIC 0x7
[ 42.552746] kvm: enabling virtualization on CPU7
[ 42.600174] kvm: disabling virtualization on CPU7
[ 42.605374] smpboot: CPU 7 is now offline
[ 42.610194] smpboot: Booting Node 0 Processor 7 APIC 0x7
[ 42.627827] kvm: enabling virtualization on CPU7
[ 42.681186] kvm: disabling virtualization on CPU7
[ 42.687093] smpboot: CPU 7 is now offline
[ 42.692417] smpboot: Booting Node 0 Processor 7 APIC 0x7
[ 42.710046] kvm: enabling virtualization on CPU7
[ 42.751031] kvm: disabling virtualization on CPU7
[ 42.756130] smpboot: CPU 7 is now offline
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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