In the later patch, we will remove noreturn attribute for die(), in order
to make each patch can be built without errors and warnings, just remove
noreturn attribute for nmi_exception_handler() earlier because it calls
die(), otherwise there exists the following build error after the later
patch:

  arch/mips/kernel/traps.c:2001:1: error: 'noreturn' function does return [-Werror]

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/mips/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 246c6a6..7a34674 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1986,7 +1986,7 @@ int register_nmi_notifier(struct notifier_block *nb)
 	return raw_notifier_chain_register(&nmi_chain, nb);
 }
 
-void __noreturn nmi_exception_handler(struct pt_regs *regs)
+void nmi_exception_handler(struct pt_regs *regs)
 {
 	char str[100];
 
-- 
2.1.0

On Mon, 14 Aug 2023, Tiezhu Yang wrote:

> In the later patch, we will remove noreturn attribute for die(), in order
> to make each patch can be built without errors and warnings, just remove
> noreturn attribute for nmi_exception_handler() earlier because it calls
> die(), otherwise there exists the following build error after the later
> patch:

 I find the wording a bit odd here, but you'll have to rewrite the change 
description for the update requested below, so let's defer any style fixes 
to v4.

>   arch/mips/kernel/traps.c:2001:1: error: 'noreturn' function does return [-Werror]

 Now that I've looked into it in detail, this change is incomplete and 
will make the kernel go astray if `nmi_exception_handler' actually ever 
does return.  See code in arch/mips/kernel/genex.S, which calls this 
function and doesn't expect it to return.  It has to be fixed before 2/3 
can be considered.  I wonder how you didn't catch it: you did check how 
this code is used, didn't you?

 Before submitting an updated version can you actually arrange for the 
NOTIFY_STOP condition to happen in your lab and verify it is handled as 
expected?  And what was the motivation for this code update, just a 
hypothetical scenario?

  Maciej

On 08/18/2023 10:39 AM, Maciej W. Rozycki wrote:
> On Mon, 14 Aug 2023, Tiezhu Yang wrote:
>
>> In the later patch, we will remove noreturn attribute for die(), in order
>> to make each patch can be built without errors and warnings, just remove
>> noreturn attribute for nmi_exception_handler() earlier because it calls
>> die(), otherwise there exists the following build error after the later
>> patch:
>
>  I find the wording a bit odd here, but you'll have to rewrite the change
> description for the update requested below, so let's defer any style fixes
> to v4.
>
>>   arch/mips/kernel/traps.c:2001:1: error: 'noreturn' function does return [-Werror]
>
>  Now that I've looked into it in detail, this change is incomplete and
> will make the kernel go astray if `nmi_exception_handler' actually ever
> does return.  See code in arch/mips/kernel/genex.S, which calls this
> function and doesn't expect it to return.  It has to be fixed before 2/3
> can be considered.  I wonder how you didn't catch it: you did check how
> this code is used, didn't you?
>

I think the proper way is to keep the noreturn attribute for
nmi_exception_handler(), and add a noreturn function BUG() at
the end of nmi_exception_handler() to make sure it does not
return.

>  Before submitting an updated version can you actually arrange for the
> NOTIFY_STOP condition to happen in your lab and verify it is handled as
> expected?  And what was the motivation for this code update, just a
> hypothetical scenario?

Yes, just a hypothetical scenario.

Thanks,
Tiezhu