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Subject: Re: [PATCH] async: Let kfree() out of the critical area of the lock
To:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
CC:     <bvanassche@acm.org>, <bhelgaas@google.com>, <dsterba@suse.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        <alexander.h.duyck@linux.intel.com>,
        <sakari.ailus@linux.intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <216356b1-38c1-8477-c4e8-03f497dd6ac8@huawei.com>
 <20190925133826.GA1496885@kroah.com>
From:   Yunfeng Ye <yeyunfeng@huawei.com>
Message-ID: <c3659e7d-0fba-ec1c-d50f-736a8c819559@huawei.com>
Date:   Wed, 25 Sep 2019 21:45:44 +0800
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On 2019/9/25 21:38, gregkh@linuxfoundation.org wrote:
> On Wed, Sep 25, 2019 at 08:52:26PM +0800, Yunfeng Ye wrote:
>> It's not necessary to put kfree() in the critical area of the lock, so
>> let it out.
>>
>> Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
>> ---
>>  kernel/async.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/async.c b/kernel/async.c
>> index 4f9c1d6..1de270d 100644
>> --- a/kernel/async.c
>> +++ b/kernel/async.c
>> @@ -135,12 +135,12 @@ static void async_run_entry_fn(struct work_struct *work)
>>  	list_del_init(&entry->domain_list);
>>  	list_del_init(&entry->global_list);
>>
>> -	/* 3) free the entry */
>> -	kfree(entry);
>>  	atomic_dec(&entry_count);
>> -
>>  	spin_unlock_irqrestore(&async_lock, flags);
>>
>> +	/* 3) free the entry */
>> +	kfree(entry);
>> +
>>  	/* 4) wake up any waiters */
>>  	wake_up(&async_done);
>>  }
>> -- 
>> 2.7.4
>>
> 
> Does this result any any measurable performance changes?
> 
No performance has been Measured at present, I just want the critical area
to be as short as possible. I think it's good to put it outside.

thanks

> thanks,
> 
> greg k-h
> 
> .
>