linux-kernel - Re: [PATCH] dmaengine: idxd: Remove a useless mutex

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Message-ID: <a9d10969-0b74-4fa1-8f3d-6fc2c7a475a7@intel.com>
Date: Mon, 4 Nov 2024 08:18:23 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>,
 Fenghua Yu <fenghua.yu@...el.com>, Vinod Koul <vkoul@...nel.org>
Cc: linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
 dmaengine@...r.kernel.org
Subject: Re: [PATCH] dmaengine: idxd: Remove a useless mutex



On 11/2/24 4:46 AM, Christophe JAILLET wrote:
> ida_alloc()/ida_free() don't need any mutex, so remove this one.
> 
> It was introduced by commit e6fd6d7e5f0f ("dmaengine: idxd: add a device to
> represent the file opened").
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>

Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> ---
> See:
> https://elixir.bootlin.com/linux/v6.11.2/source/lib/idr.c#L375
> https://elixir.bootlin.com/linux/v6.11.2/source/lib/idr.c#L484
> ---
>  drivers/dma/idxd/cdev.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
> index 57f1bf2ab20b..ff94ee892339 100644
> --- a/drivers/dma/idxd/cdev.c
> +++ b/drivers/dma/idxd/cdev.c
> @@ -28,7 +28,6 @@ struct idxd_cdev_context {
>   * global to avoid conflict file names.
>   */
>  static DEFINE_IDA(file_ida);
> -static DEFINE_MUTEX(ida_lock);
>  
>  /*
>   * ictx is an array based off of accelerator types. enum idxd_type
> @@ -123,9 +122,7 @@ static void idxd_file_dev_release(struct device *dev)
>  	struct idxd_device *idxd = wq->idxd;
>  	int rc;
>  
> -	mutex_lock(&ida_lock);
>  	ida_free(&file_ida, ctx->id);
> -	mutex_unlock(&ida_lock);
>  
>  	/* Wait for in-flight operations to complete. */
>  	if (wq_shared(wq)) {
> @@ -284,9 +281,7 @@ static int idxd_cdev_open(struct inode *inode, struct file *filp)
>  	}
>  
>  	idxd_cdev = wq->idxd_cdev;
> -	mutex_lock(&ida_lock);
>  	ctx->id = ida_alloc(&file_ida, GFP_KERNEL);
> -	mutex_unlock(&ida_lock);
>  	if (ctx->id < 0) {
>  		dev_warn(dev, "ida alloc failure\n");
>  		goto failed_ida;