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Date: Fri, 8 May 2009 11:04:24 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Shaohua Li <shaohua.li@...el.com>
Cc: lkml <linux-kernel@...r.kernel.org>,
Andi Kleen <andi@...stfloor.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86 MCE: shut up lockdep warning
* Shaohua Li <shaohua.li@...el.com> wrote:
> lockdep report below warning when I try to offline one cpu:
> [ 110.835487] =================================
> [ 110.835616] [ INFO: inconsistent lock state ]
> [ 110.835688] 2.6.30-rc4-00336-g8c9ed89 #52
> [ 110.835757] ---------------------------------
> [ 110.835828] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
> [ 110.835908] swapper/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
> [ 110.835982] (cmci_discover_lock){?.+...}, at: [<ffffffff80236dc0>] cmci_clear+0x30/0x9b
>
> smp_call_function_single() will disable interrupt. moving mce reenable/disable
> to workqueue, so no irq is disabled.
>
> Signed-off-by: Shaohua Li<shaohua.li@...el.com>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_64.c b/arch/x86/kernel/cpu/mcheck/mce_64.c
> index 6fb0b35..739c824 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_64.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_64.c
> @@ -1057,30 +1057,32 @@ static __cpuinit void mce_remove_device(unsigned int cpu)
> }
>
> /* Make sure there are no machine checks on offlined CPUs. */
> -static void mce_disable_cpu(void *h)
> +static long mce_disable_cpu(void *h)
> {
> int i;
> unsigned long action = *(unsigned long *)h;
>
> if (!mce_available(¤t_cpu_data))
> - return;
> + return 0;
> if (!(action & CPU_TASKS_FROZEN))
> cmci_clear();
> for (i = 0; i < banks; i++)
> wrmsrl(MSR_IA32_MC0_CTL + i*4, 0);
> + return 0;
> }
>
> -static void mce_reenable_cpu(void *h)
> +static long mce_reenable_cpu(void *h)
> {
> int i;
> unsigned long action = *(unsigned long *)h;
>
> if (!mce_available(¤t_cpu_data))
> - return;
> + return 0;
> if (!(action & CPU_TASKS_FROZEN))
> cmci_reenable();
> for (i = 0; i < banks; i++)
> wrmsrl(MSR_IA32_MC0_CTL + i*4, bank[i]);
> + return 0;
> }
>
> /* Get notified when a cpu comes on/off. Be hotplug friendly. */
> @@ -1106,14 +1108,14 @@ static int __cpuinit mce_cpu_callback(struct notifier_block *nfb,
> case CPU_DOWN_PREPARE:
> case CPU_DOWN_PREPARE_FROZEN:
> del_timer_sync(t);
> - smp_call_function_single(cpu, mce_disable_cpu, &action, 1);
> + work_on_cpu(cpu, mce_disable_cpu, &action);
> break;
> case CPU_DOWN_FAILED:
> case CPU_DOWN_FAILED_FROZEN:
> t->expires = round_jiffies(jiffies +
> __get_cpu_var(next_interval));
> add_timer_on(t, cpu);
> - smp_call_function_single(cpu, mce_reenable_cpu, &action, 1);
> + work_on_cpu(cpu, mce_reenable_cpu, &action);
> break;
No, this needs a real fix - not a 'shut up lockdep' workaround.
One problem is that cmci_discover_lock is taken irq-unsafe, which is
obviously a bad idea ...
Could you please try the fix for that from Hidetoshi-san, attached
below (also available in latest -tip).
Thanks,
Ingo
------------------>
>From e5299926d7459d9fa7c7f856983147817aedb10e Mon Sep 17 00:00:00 2001
From: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Date: Fri, 8 May 2009 17:28:40 +0900
Subject: [PATCH] x86: MCE: make cmci_discover_lock irq-safe
Lockdep reports the warning below when Li tries to offline one cpu:
[ 110.835487] =================================
[ 110.835616] [ INFO: inconsistent lock state ]
[ 110.835688] 2.6.30-rc4-00336-g8c9ed89 #52
[ 110.835757] ---------------------------------
[ 110.835828] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
[ 110.835908] swapper/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
[ 110.835982] (cmci_discover_lock){?.+...}, at: [<ffffffff80236dc0>] cmci_clear+0x30/0x9b
cmci_clear() can be called via smp_call_function_single().
It is better to disable interrupt while holding cmci_discover_lock,
to turn it into an irq-safe lock - we can deadlock otherwise.
[ Impact: fix possible deadlock in the MCE code ]
Reported-by: Shaohua Li <shaohua.li@...el.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
LKML-Reference: <4A03ED38.8000700@...fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Reported-by: Shaohua Li<shaohua.li@...el.com>
---
arch/x86/kernel/cpu/mcheck/mce_intel_64.c | 10 ++++++----
1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel_64.c b/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
index d6b72df..cef3ee3 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
@@ -151,10 +151,11 @@ static void print_update(char *type, int *hdr, int num)
static void cmci_discover(int banks, int boot)
{
unsigned long *owned = (void *)&__get_cpu_var(mce_banks_owned);
+ unsigned long flags;
int hdr = 0;
int i;
- spin_lock(&cmci_discover_lock);
+ spin_lock_irqsave(&cmci_discover_lock, flags);
for (i = 0; i < banks; i++) {
u64 val;
@@ -184,7 +185,7 @@ static void cmci_discover(int banks, int boot)
WARN_ON(!test_bit(i, __get_cpu_var(mce_poll_banks)));
}
}
- spin_unlock(&cmci_discover_lock);
+ spin_unlock_irqrestore(&cmci_discover_lock, flags);
if (hdr)
printk(KERN_CONT "\n");
}
@@ -211,13 +212,14 @@ void cmci_recheck(void)
*/
void cmci_clear(void)
{
+ unsigned long flags;
int i;
int banks;
u64 val;
if (!cmci_supported(&banks))
return;
- spin_lock(&cmci_discover_lock);
+ spin_lock_irqsave(&cmci_discover_lock, flags);
for (i = 0; i < banks; i++) {
if (!test_bit(i, __get_cpu_var(mce_banks_owned)))
continue;
@@ -227,7 +229,7 @@ void cmci_clear(void)
wrmsrl(MSR_IA32_MC0_CTL2 + i, val);
__clear_bit(i, __get_cpu_var(mce_banks_owned));
}
- spin_unlock(&cmci_discover_lock);
+ spin_unlock_irqrestore(&cmci_discover_lock, flags);
}
/*
--
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