linux-kernel - 回复: [PATCH v3] debugobjects: install CPU hotplug callback

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Date:   Thu, 10 Sep 2020 01:48:54 +0000
From:   "Zhang, Qiang" <Qiang.Zhang@...driver.com>
To:     Waiman Long <longman@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "elver@...gle.com" <elver@...gle.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: 回复: [PATCH v3] debugobjects: install CPU hotplug callback



________________________________________
发件人: Waiman Long <longman@...hat.com>
发送时间: 2020年9月9日 2:23
收件人: Zhang, Qiang; tglx@...utronix.de; mingo@...nel.org; elver@...gle.com
抄送: linux-kernel@...r.kernel.org
主题: Re: [PATCH v3] debugobjects: install CPU hotplug callback

On 9/8/20 2:27 AM, qiang.zhang@...driver.com wrote:
> From: Zqiang <qiang.zhang@...driver.com>
>
> Due to CPU hotplug, it may never be online after it's offline,
> some objects in percpu pool is never free. in order to avoid
> this happening, install CPU hotplug callback, call this callback
> func to free objects in percpu pool when CPU going offline.
>
> Signed-off-by: Zqiang <qiang.zhang@...driver.com>
> ---
>   v1->v2:
>   Modify submission information.
>
>   v2->v3:
>   In CPU hotplug callback func, add clear percpu pool "obj_free" operation.
>   capitalize 'CPU', and use shorter preprocessor sequence.
>
>   include/linux/cpuhotplug.h |  1 +
>   lib/debugobjects.c         | 24 ++++++++++++++++++++++++
>   2 files changed, 25 insertions(+)
>
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 3215023d4852..0c39d57e5342 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -36,6 +36,7 @@ enum cpuhp_state {
>       CPUHP_X86_MCE_DEAD,
>       CPUHP_VIRT_NET_DEAD,
>       CPUHP_SLUB_DEAD,
> +     CPUHP_DEBUG_OBJ_DEAD,
>       CPUHP_MM_WRITEBACK_DEAD,
>       CPUHP_MM_VMSTAT_DEAD,
>       CPUHP_SOFTIRQ_DEAD,
> diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> index fe4557955d97..bb69a02c3e7b 100644
> --- a/lib/debugobjects.c
> +++ b/lib/debugobjects.c
> @@ -19,6 +19,7 @@
>   #include <linux/slab.h>
>   #include <linux/hash.h>
>   #include <linux/kmemleak.h>
> +#include <linux/cpu.h>
>
>   #define ODEBUG_HASH_BITS    14
>   #define ODEBUG_HASH_SIZE    (1 << ODEBUG_HASH_BITS)
> @@ -433,6 +434,24 @@ static void free_object(struct debug_obj *obj)
>       }
>   }
>
> +#ifdef CONFIG_HOTPLUG_CPU
> +static int object_cpu_offline(unsigned int cpu)
> +{
> +     struct debug_percpu_free *percpu_pool;
> +     struct hlist_node *tmp;
> +     struct debug_obj *obj;
> +
> +     percpu_pool = per_cpu_ptr(&percpu_obj_pool, cpu);
> +     hlist_for_each_entry_safe(obj, tmp, &percpu_pool->free_objs, node) {
> +             hlist_del(&obj->node);
> +             kmem_cache_free(obj_cache, obj);
> +     }
> +     percpu_pool->obj_free = 0;

>>For pointer, it is better to use NULL for clarity.

>>Cheers,
>>Longman

Do you mean "->obj_free" variable ?   this represents the number of free objects in  percpu_pool .

> +
> +     return 0;
> +}
> +#endif
> +
>   /*
>    * We run out of memory. That means we probably have tons of objects
>    * allocated.
> @@ -1367,6 +1386,11 @@ void __init debug_objects_mem_init(void)
>       } else
>               debug_objects_selftest();
>
> +#ifdef CONFIG_HOTPLUG_CPU
> +     cpuhp_setup_state_nocalls(CPUHP_DEBUG_OBJ_DEAD, "object:offline", NULL,
> +                                     object_cpu_offline);
> +#endif
> +
>       /*
>        * Increase the thresholds for allocating and freeing objects
>        * according to the number of possible CPUs available in the system.