linux-kernel - Re: [PATCH 1/2] bdisp: Fix a possible sleep-in-atomic bug in bdisp_hw

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Date:   Sat, 16 Dec 2017 19:53:55 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Fabien DESSENNE <fabien.dessenne@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Benjamin GAIGNARD <benjamin.gaignard@...com>,
        Hans Verkuil <hverkuil@...all.nl>
Subject: Re: [PATCH 1/2] bdisp: Fix a possible sleep-in-atomic bug in
 bdisp_hw_reset

Hi,

On 2017/12/15 22:51, Fabien DESSENNE wrote:
> Hi
>
> On 12/12/17 14:47, Jia-Ju Bai wrote:
>> The driver may sleep under a spinlock.
>> The function call path is:
>> bdisp_device_run (acquire the spinlock)
>>     bdisp_hw_reset
>>       msleep --> may sleep
>>
>> To fix it, msleep is replaced with mdelay.
> May I suggest you to use readl_poll_timeout_atomic (instead of the whole
> "for" block): this fixes the problem and simplifies the code?

Okay, I have submitted a patch according to your advice.
You can have a look :)


Thanks,
Jia-Ju Bai


>> This bug is found by my static analysis tool(DSAC) and checked by my code review.
>>
>> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
>> ---
>>    drivers/media/platform/sti/bdisp/bdisp-hw.c |    2 +-
>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/platform/sti/bdisp/bdisp-hw.c b/drivers/media/platform/sti/bdisp/bdisp-hw.c
>> index b7892f3..4b62ceb 100644
>> --- a/drivers/media/platform/sti/bdisp/bdisp-hw.c
>> +++ b/drivers/media/platform/sti/bdisp/bdisp-hw.c
>> @@ -382,7 +382,7 @@ int bdisp_hw_reset(struct bdisp_dev *bdisp)
>>    	for (i = 0; i < POLL_RST_MAX; i++) {
>>    		if (readl(bdisp->regs + BLT_STA1) & BLT_STA1_IDLE)
>>    			break;
>> -		msleep(POLL_RST_DELAY_MS);
>> +		mdelay(POLL_RST_DELAY_MS);
>>    	}
>>    	if (i == POLL_RST_MAX)
>>    		dev_err(bdisp->dev, "Reset timeout\n");