linux-kernel - Re: [PATCH] mm: slub: add panic_on

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Message-ID: <20200501214144.GD27720@optiplex-lnx>
Date:   Fri, 1 May 2020 17:41:44 -0400
From:   Rafael Aquini <aquini@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        iamjoonsoo.kim@....com, rientjes@...gle.com, penberg@...nel.org,
        cl@...ux.com
Subject: Re: [PATCH] mm: slub: add panic_on_error to the debug facilities

On Fri, May 01, 2020 at 02:37:51PM -0700, Andrew Morton wrote:
> On Fri,  1 May 2020 17:15:40 -0400 Rafael Aquini <aquini@...hat.com> wrote:
> 
> > Sometimes it is desirable to override SLUB's debug facilities
> > default behavior upon stumbling on a cache or object error
> > and just stop the execution in order to grab a coredump, at
> > the error-spotting time, instead of trying to fix the issue
> > and report in an attempt to keep the system rolling.
> > 
> > This patch introduces a new debug flag SLAB_PANIC_ON_ERROR,
> > along with its related SLUB-machinery, in order to extend
> > current slub_debug facilites and provide the aforementioned
> > behavior override.
> > 
> 
> Sees reasonable.
> 
> > --- a/Documentation/vm/slub.rst
> > +++ b/Documentation/vm/slub.rst
> > @@ -54,6 +54,8 @@ Possible debug options are::
> >  			caused higher minimum slab orders
> >  	-		Switch all debugging off (useful if the kernel is
> >  			configured with CONFIG_SLUB_DEBUG_ON)
> > +	C		Toggle panic on error (crash) to allow for post-mortem
> > +			analysis of a coredump taken at the error-spotting time
> 
> nit: "toggle" means to switch to the other state.  But what we're doing
> here is to set to the "on" state.  This:
>

Thanks Andrew, that's indeed much better.
 
> --- a/Documentation/vm/slub.rst~mm-slub-add-panic_on_error-to-the-debug-facilities-fix
> +++ a/Documentation/vm/slub.rst
> @@ -49,12 +49,12 @@ Possible debug options are::
>  	P		Poisoning (object and padding)
>  	U		User tracking (free and alloc)
>  	T		Trace (please only use on single slabs)
> -	A		Toggle failslab filter mark for the cache
> +	A		Enable failslab filter mark for the cache
>  	O		Switch debugging off for caches that would have
>  			caused higher minimum slab orders
>  	-		Switch all debugging off (useful if the kernel is
>  			configured with CONFIG_SLUB_DEBUG_ON)
> -	C		Toggle panic on error (crash) to allow for post-mortem
> +	C		Enable panic on error (crash) to allow for post-mortem
>  			analysis of a coredump taken at the error-spotting time
>  
>  F.e. in order to boot just with sanity checks and red zoning one would specify::
> _
> 
>