[PATCH] ARM: s3c: irq-s3c24xx: Fix return value check for s3c24xx_init_intc()

[Jackie Liu]

Hi Krzysztof, Thanks for you message.

在 2021/9/1 下午8:09, Krzysztof Kozlowski 写道:
> On 31/08/2021 11:57, Jackie Liu wrote:
>> From: Jackie Liu <liuyun01 at kylinos.cn>
>>
>> The s3c24xx_init_intc() returns an error pointer upon failure, not NULL.
>> let's add an error pointer check in s3c24xx_handle_irq.
>>
>> Fixes: 1f629b7a3ced ("ARM: S3C24XX: transform irq handling into a declarative form")
>> Signed-off-by: Jackie Liu <liuyun01 at kylinos.cn>
> 
> Please use scripts/get_maintainers.pl to get list of mailing lists to
> CC. You skipped two - arm and LKML.
> 
>> ---
>>   arch/arm/mach-s3c/irq-s3c24xx.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/mach-s3c/irq-s3c24xx.c b/arch/arm/mach-s3c/irq-s3c24xx.c
>> index 0c631c14a817..d58bf0f9bf9a 100644
>> --- a/arch/arm/mach-s3c/irq-s3c24xx.c
>> +++ b/arch/arm/mach-s3c/irq-s3c24xx.c
>> @@ -362,11 +362,11 @@ static inline int s3c24xx_handle_intc(struct s3c_irq_intc *intc,
>>   static asmlinkage void __exception_irq_entry s3c24xx_handle_irq(struct pt_regs *regs)
>>   {
>>   	do {
>> -		if (likely(s3c_intc[0]))
>> +		if (likely(!IS_ERR_OR_NULL(s3c_intc[0])))
>>   			if (s3c24xx_handle_intc(s3c_intc[0], regs, 0))
> 
> Thanks for the patch but it does not look entirely correct.
> 
> For platform based machines, neither ERR nor NULL can happen here.
> The s3c24xx_handle_irq() will be set as IRQ handler iff this succeeds:
>      s3c_intc[0] = s3c24xx_init_intc()
> 
> If this fails, the next calls to s3c24xx_init_intc() won't be executed.
> 
> For DT machine, s3c_init_intc_of() could set the IRQ handler without
> setting s3c_intc[0] only if it was called with num_ctrl=0. There is no
> such code path, so again the s3c_intc[0] will have a valid pointer if
> set_handle_irq() is called.
> 
> Therefore in s3c24xx_handle_irq(), the s3c_intc[0] is always something.
> 
> The code can be simplified by removing if(), if we really wanted and
> were sure about it.

In fact, I didn't study his underlying logic in depth, but found that
this place was not particularly perfect based on the return value of the
function, because I happened to encounter a similar problem elsewhere.

> 
> 
>>   				continue;
>>   
>> -		if (s3c_intc[2])
>> +		if (!IS_ERR_OR_NULL(s3c_intc[2]))
> 
> For the non-DT case, this seems ugly but proper solution. The
> s3c_intc[2] could be NULL (not set at all) or set as ERR (if
> s3c24xx_init_intc() fails).
> 
>>   			if (s3c24xx_handle_intc(s3c_intc[2], regs, 64))
>>   				continue;
>>   
>>
> 
> 
> Best regards,
> Krzysztof
> 

Would you mind review v2?

--------------------------------------------------------------

diff --git a/arch/arm/mach-s3c/irq-s3c24xx.c 
b/arch/arm/mach-s3c/irq-s3c24xx.c
index 0c631c14a817..df471d322493 100644
--- a/arch/arm/mach-s3c/irq-s3c24xx.c
+++ b/arch/arm/mach-s3c/irq-s3c24xx.c
@@ -362,11 +362,24 @@ static inline int s3c24xx_handle_intc(struct 
s3c_irq_intc *intc,
  static asmlinkage void __exception_irq_entry s3c24xx_handle_irq(struct 
pt_regs *regs)
  {
         do {
-               if (likely(s3c_intc[0]))
-                       if (s3c24xx_handle_intc(s3c_intc[0], regs, 0))
-                               continue;
+               /* For platform based machines, neither ERR nor NULL can 
happen here.
+                * The s3c24xx_handle_irq() will be set as IRQ handler 
iff this succeeds:
+                *
+                *    s3c_intc[0] = s3c24xx_init_intc()
+                *
+                * If this fails, the next calls to s3c24xx_init_intc() 
won't be executed.
+                *
+                * For DT machine, s3c_init_intc_of() could set the IRQ 
handler without
+                * setting s3c_intc[0] only if it was called with 
num_ctrl=0. There is no
+                * such code path, so again the s3c_intc[0] will have a 
valid pointer if
+                * set_handle_irq() is called.
+                *
+                * Therefore in s3c24xx_handle_irq(), the s3c_intc[0] is 
always something.
+                */
+               if (s3c24xx_handle_intc(s3c_intc[0], regs, 0))
+                       continue;

-               if (s3c_intc[2])
+               if (!IS_ERR_OR_NULL(s3c_intc[2]))
                         if (s3c24xx_handle_intc(s3c_intc[2], regs, 64))
                                 continue;


---
Thanks, Jackie