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Message-ID: <515AE64B.7080804@linux.vnet.ibm.com>
Date: Tue, 02 Apr 2013 19:38:11 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>
CC: Chen Gong <gong.chen@...ux.intel.com>,
Dave Jones <davej@...hat.com>,
Linux Kernel <linux-kernel@...r.kernel.org>, x86@...nel.org,
Thomas Gleixner <tglx@...utronix.de>, andi@...stfloor.org,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
tony.luck@...il.com
Subject: Re: [PATCH] x86/mce: Rework cmci_rediscover() to play well with CPU
hotplug
On 03/20/2013 03:31 PM, Srivatsa S. Bhat wrote:
[...]
> ------------------------------------------------------------>
>
> From: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> Subject: [PATCH] x86/mce: Rework cmci_rediscover() to play well with CPU hotplug
>
> Dave Jones reports that offlining a CPU leads to this trace:
>
> numa_remove_cpu cpu 1 node 0: mask now 0,2-3
> smpboot: CPU 1 is now offline
> BUG: using smp_processor_id() in preemptible [00000000] code:
> cpu-offline.sh/10591
> caller is cmci_rediscover+0x6a/0xe0
> Pid: 10591, comm: cpu-offline.sh Not tainted 3.9.0-rc3+ #2
> Call Trace:
> [<ffffffff81333bbd>] debug_smp_processor_id+0xdd/0x100
> [<ffffffff8101edba>] cmci_rediscover+0x6a/0xe0
> [<ffffffff815f5b9f>] mce_cpu_callback+0x19d/0x1ae
> [<ffffffff8160ea66>] notifier_call_chain+0x66/0x150
> [<ffffffff8107ad7e>] __raw_notifier_call_chain+0xe/0x10
> [<ffffffff8104c2e3>] cpu_notify+0x23/0x50
> [<ffffffff8104c31e>] cpu_notify_nofail+0xe/0x20
> [<ffffffff815ef082>] _cpu_down+0x302/0x350
> [<ffffffff815ef106>] cpu_down+0x36/0x50
> [<ffffffff815f1c9d>] store_online+0x8d/0xd0
> [<ffffffff813edc48>] dev_attr_store+0x18/0x30
> [<ffffffff81226eeb>] sysfs_write_file+0xdb/0x150
> [<ffffffff811adfb2>] vfs_write+0xa2/0x170
> [<ffffffff811ae16c>] sys_write+0x4c/0xa0
> [<ffffffff81613019>] system_call_fastpath+0x16/0x1b
>
>
> However, a look at cmci_rediscover shows that it can be simplified quite
> a bit, apart from solving the above issue. It invokes functions that
> take spin locks with interrupts disabled, and hence it can run in atomic
> context. Also, it is run in the CPU_POST_DEAD phase, so the dying CPU
> is already dead and out of the cpu_online_mask. So take these points into
> account and simplify the code, and thereby also fix the above issue.
>
> Reported-by: Dave Jones <davej@...hat.com>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
>
> arch/x86/include/asm/mce.h | 4 ++--
> arch/x86/kernel/cpu/mcheck/mce.c | 2 +-
> arch/x86/kernel/cpu/mcheck/mce_intel.c | 25 +++++--------------------
> 3 files changed, 8 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
> index f4076af..fa5f71e 100644
> --- a/arch/x86/include/asm/mce.h
> +++ b/arch/x86/include/asm/mce.h
> @@ -146,13 +146,13 @@ DECLARE_PER_CPU(struct device *, mce_device);
> void mce_intel_feature_init(struct cpuinfo_x86 *c);
> void cmci_clear(void);
> void cmci_reenable(void);
> -void cmci_rediscover(int dying);
> +void cmci_rediscover(void);
> void cmci_recheck(void);
> #else
> static inline void mce_intel_feature_init(struct cpuinfo_x86 *c) { }
> static inline void cmci_clear(void) {}
> static inline void cmci_reenable(void) {}
> -static inline void cmci_rediscover(int dying) {}
> +static inline void cmci_rediscover(void) {}
> static inline void cmci_recheck(void) {}
> #endif
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 7bc1263..9239504 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -2358,7 +2358,7 @@ mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
>
> if (action == CPU_POST_DEAD) {
> /* intentionally ignoring frozen here */
> - cmci_rediscover(cpu);
> + cmci_rediscover();
> }
>
> return NOTIFY_OK;
> diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
> index 402c454..ae1697c 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
> @@ -285,39 +285,24 @@ void cmci_clear(void)
> raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
> }
>
> -static long cmci_rediscover_work_func(void *arg)
> +static void cmci_rediscover_work_func(void *arg)
> {
> int banks;
>
> /* Recheck banks in case CPUs don't all have the same */
> if (cmci_supported(&banks))
> cmci_discover(banks);
> -
> - return 0;
> }
>
> -/*
> - * After a CPU went down cycle through all the others and rediscover
> - * Must run in process context.
> - */
> -void cmci_rediscover(int dying)
> +/* After a CPU went down cycle through all the others and rediscover */
> +void cmci_rediscover(void)
> {
> - int cpu, banks;
> + int banks;
>
> if (!cmci_supported(&banks))
> return;
>
> - for_each_online_cpu(cpu) {
> - if (cpu == dying)
> - continue;
> -
> - if (cpu == smp_processor_id()) {
> - cmci_rediscover_work_func(NULL);
> - continue;
> - }
> -
> - work_on_cpu(cpu, cmci_rediscover_work_func, NULL);
> - }
> + on_each_cpu(cmci_rediscover_work_func, NULL, 1);
> }
>
> /*
>
Hi Boris,
Tony mentioned that this patch worked fine for him. So could you kindly
pick up this patch?
Regards,
Srivatsa S. Bhat
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