linux-kernel - Re: [PATCH] dma/ipu: change ipu_irq_handler() to remove compile warning

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Message-Id: <E4E2576D-A6F4-4B64-9E96-6640A525D028@gmail.com>
Date:	Tue, 25 Aug 2015 16:16:01 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	vinod.koul@...el.com, dan.j.williams@...el.com, robh@...nel.org,
	jiang.liu@...ux.intel.com, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma/ipu: change ipu_irq_handler() to remove compile warning


> On Aug 25, 2015, at 16:07, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> On Tue, 25 Aug 2015, yalin wang wrote:
>> Change ipu_irq_handler() to avoid gcc warning:
>> 
>> drivers/dma/ipu/ipu_irq.c:305:4: warning: 'irq' may be used
>> uninitialized in this function [-Wmaybe-uninitialized]
>>    generic_handle_irq(irq);
> 
> That's a false positive from GCC. irq is always initialized when
> generic_handle_irq() is called.
> 
>> Signed-off-by: yalin wang <yalin.wang2010@...il.com>
>> ---
>> drivers/dma/ipu/ipu_irq.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/dma/ipu/ipu_irq.c b/drivers/dma/ipu/ipu_irq.c
>> index 7489d2a..1a74eee 100644
>> --- a/drivers/dma/ipu/ipu_irq.c
>> +++ b/drivers/dma/ipu/ipu_irq.c
>> @@ -286,23 +286,21 @@ static void ipu_irq_handler(unsigned int __irq, struct irq_desc *desc)
>> 		raw_spin_unlock(&bank_lock);
>> 		while ((line = ffs(status))) {
>> 			struct ipu_irq_map *map;
>> -			unsigned int irq;
>> 
>> 			line--;
>> 			status &= ~(1UL << line);
>> 
>> 			raw_spin_lock(&bank_lock);
>> 			map = src2map(32 * i + line);
>> -			if (map)
>> -				irq = map->irq;
>> 			raw_spin_unlock(&bank_lock);
>> 
>> 			if (!map) {
>> 				pr_err("IPU: Interrupt on unmapped source %u bank %d\n",
>> 				       line, i);
>> 				continue;
>> +			} else {
>> +				generic_handle_irq(map->irq);
> 
> So you change that from retrieving the irq number with bank lock held
> to an unprotected access.

i see,
i will send a V2 patch .

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