Re: [PATCH 1/3] powerpc: Properly return error code from do_patch_instruction()

["Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>]

Hi Steve,

Steven Rostedt wrote:
> On Thu, 23 Apr 2020 18:21:14 +0200
> Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> 
>> Le 23/04/2020 à 17:09, Naveen N. Rao a écrit :
>> > With STRICT_KERNEL_RWX, we are currently ignoring return value from
>> > __patch_instruction() in do_patch_instruction(), resulting in the error
>> > not being propagated back. Fix the same.  
>> 
>> Good patch.
>> 
>> Be aware that there is ongoing work which tend to wanting to replace 
>> error reporting by BUG_ON() . See 
>> https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=166003
> 
> Thanks for the reference. I still believe that WARN_ON() should be used in
> 99% of the cases, including here. And only do a BUG_ON() when you know
> there's no recovering from it.

I'm not sure if you meant that we should have a WARN_ON() in 
patch_instruction(), or if it was about the users of 
patch_instruction(). As you're well aware, ftrace likes to do its own 
WARN_ON() if any of its operations fail through ftrace_bug(). That was 
the reason I didn't add anything here.


- Naveen