Re: [PATCH v3 1/3] MIPS: Remove noreturn attribute for nmi_exception_handler()

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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

 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

 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.


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