Re: [PATCH] async: Let kfree() out of the critical area of the lock

From: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To: Yunfeng Ye <yeyunfeng@huawei.com>
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>
Subject: Re: [PATCH] async: Let kfree() out of the critical area of the lock
Date: Wed, 25 Sep 2019 15:38:26 +0200	[thread overview]
Message-ID: <20190925133826.GA1496885@kroah.com> (raw)
In-Reply-To: <216356b1-38c1-8477-c4e8-03f497dd6ac8@huawei.com>

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?

thanks,

greg k-h