Re: [patch] drm/msm/dsi: free first element on error

From: walter harms <wharms@bfs.de>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>,
	Rob Clark <robdclark@gmail.com>,
	Archit Taneja <architt@codeaurora.org>,
	linux-arm-msm@vger.kernel.org, kernel-janitors@vger.kernel.org,
	dri-devel@lists.freedesktop.org,
	Wei Yongjun <yongjun_wei@trendmicro.com.cn>,
	freedreno@lists.freedesktop.org
Subject: Re: [patch] drm/msm/dsi: free first element on error
Date: Thu, 16 Feb 2017 13:03:56 +0100	[thread overview]
Message-ID: <58A5952C.105@bfs.de> (raw)
In-Reply-To: <20170216115307.GD4108@mwanda>

Am 16.02.2017 12:53, schrieb Dan Carpenter:
> On Thu, Feb 16, 2017 at 01:27:47PM +0200, Jani Nikula wrote:
>> On Thu, 16 Feb 2017, Dan Carpenter <dan.carpenter@oracle.com> wrote:
>>> We want to free msm_host->bus_clks[0] so the > should be >=.
>>>
>>> Fixes: 6e0eb52eba9e ("drm/msm/dsi: Parse bus clocks from a list")
>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>>
>>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>> index 1fc07ce24686..239e79b39a45 100644
>>> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
>>> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
>>> @@ -437,7 +437,7 @@ static int dsi_bus_clk_enable(struct msm_dsi_host *msm_host)
>>>  
>>>  	return 0;
>>>  err:
>>> -	for (; i > 0; i--)
>>> +	for (; i >= 0; i--)
>>>  		clk_disable_unprepare(msm_host->bus_clks[i]);
>>
>> By the looks of it this is also wrong. I didn't look at the functions,
>> but you probably don't want to unprepare something where prepare failed,
>> i.e. you want to -1 both the start and end offsets. Perhaps the right
>> fix is
>>
>> 	while (i--)
>> 		clk_disable_unprepare(msm_host->bus_clks[i]);
>>
>> which also seems to be widely used on error paths.
>>
> 

We already know that programmers are bad in counting backwards ...

any chance to make that into a forward loop ?

re,
 wh