Re: [PATCH] Support resetting WARN_ONCE for all architectures

[Michael Ellerman]

Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:
> On Fri, 03 Nov 2017 20:38:03 +1100 Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote:
>> Andi Kleen <andi@xxxxxxxxxxxxxx> writes:
>> > diff --git a/lib/bug.c b/lib/bug.c
>> > index a6a1137d06db..7cb2d41845f7 100644
>> > --- a/lib/bug.c
>> > +++ b/lib/bug.c
>> > @@ -195,3 +195,24 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
>> >  
>> >  	return BUG_TRAP_TYPE_BUG;
>> >  }
>> > +
>> > +static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
>> > +{
>> > +	struct bug_entry *bug;
>> > +
>> > +	for (bug = start; bug < end; bug++)
>> > +		bug->flags &= ~BUGFLAG_ONCE;
>> 
>> Clearing BUGFLAG_ONCE removes the once-ness permanently. ie. it becomes
>> a WARN().
>> 
>> You should be clearing BUGFLAG_DONE, which is the flag that says this
>> WARN has already triggered.
>
> This?

Yes.

> --- a/lib/bug.c~support-resetting-warn_once-for-all-architectures-v2-fix-fix-fix
> +++ a/lib/bug.c
> @@ -202,7 +202,7 @@ static void clear_once_table(struct bug_
>  	struct bug_entry *bug;
>  
>  	for (bug = start; bug < end; bug++)
> -		bug->flags &= ~BUGFLAG_ONCE;
> +		bug->flags &= ~BUGFLAG_DONE;
>  }
>  
>  void generic_bug_clear_once(void)
>
>
> And this is getting a bit nutty:
>
> support-resetting-warn_once.patch
> support-resetting-warn_once-checkpatch-fixes.patch
> support-resetting-warn_once-for-all-architectures.patch
> support-resetting-warn_once-for-all-architectures-v2.patch
> support-resetting-warn_once-for-all-architectures-v2-fix.patch
> support-resetting-warn_once-for-all-architectures-v2-fix-fix.patch
> support-resetting-warn_once-for-all-architectures-v2-fix-fix-fix.patch

Quite. They should probably all just be squashed together.

> I'll push all this at Stephen later today.  Someone please tell me
> whether this code actually works!

I've tested Andi's two patches with the above one-liner and that worked
for me. I'll test again on linux-next once it's in there to confirm.

cheers