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

Hi Krzysztof, Thanks for you message.

��� 2021/9/1 ������8:09, Krzysztof Kozlowski ������:

On 31/08/2021 11:57, Jackie Liu wrote:

quoted

From: Jackie Liu <redacted>

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 <redacted>

Please use scripts/get_maintainers.pl to get list of mailing lists to
CC. You skipped two - arm and LKML.

quoted

---
  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.

quoted

  				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).

quoted

  			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