Re: [RFC PATCH v3 11/12] powerpc: Remove unreachable() from WARN_ON()

[Sathvika Vasireddy <sv@linux.vnet.ibm.com>]

Hi Chen,

Thanks for pitching in and providing your inputs :-)

On 01/07/22 07:43, Chen Zhongjin wrote:
> Hi everyone,
>
> Hope I'm not too late for this discussion.
>
> I'm not familiar with ppc so it spent me some time to reproduce this. 
> But at last I didn't make it.
>
> What I did:
>
> 1 checkout to tip/objtool/core
>
> 2 apply this patch
>
> 3 recover the unreachable() after WARN_ENTRY(..
>
> 4 compile on defconfig/allyesconfig
>
> If anyone can point out which file will generate this problem it will 
> be perfect.

To reproduce this problem, you may want to apply this patch series on 
top of objtool/core branch of the tip tree, and compile on 
ppc64le_defconfig.

There are a couple of C files that are generating these warnings. One 
such file is: arch/powerpc/kvm/../../../virt/kvm/kvm_main.o which gives
*arch/powerpc/kvm/../../../virt/kvm/kvm_main.o: warning: objtool: 
kvm_mmu_notifier_release+0x6c: unannotated intra-function call* warning.

With unreachable() in __WARN_FLAGS(), we get unannotated intra-function 
call warnings, but without unreachable() like in patch 11/12 or with 
just the builtin variant of unreachable (__builtin_unreachable()) 
instead of unreachable(), we do not get those warnings.


- Sathvika