linux-kernel - Re: [PATCH] Support resetting WARN

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Date:   Fri, 3 Nov 2017 10:47:55 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH] Support resetting WARN_ONCE for all architectures

On Fri, 03 Nov 2017 20:38:03 +1100 Michael Ellerman <mpe@...erman.id.au> wrote:

> Hi Andi,
> 
> Thanks for making it work with the flag, but ...
> 
> Andi Kleen <andi@...stfloor.org> 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?

--- 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

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