From: Michal Hocko <mhocko@kernel.org>
To: Leon Romanovsky <leon@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>, Vlastimil Babka <vbabka@suse.cz>,
Linux MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm/slub: Add a dump_stack() to the unexpected GFP check
Date: Mon, 16 Jan 2017 10:59:25 +0100 [thread overview]
Message-ID: <20170116095925.GE13641@dhcp22.suse.cz> (raw)
In-Reply-To: <20170116094851.GD32481@mtr-leonro.local>
On Mon 16-01-17 11:48:51, Leon Romanovsky wrote:
> On Mon, Jan 16, 2017 at 10:37:02AM +0100, Borislav Petkov wrote:
> > On Mon, Jan 16, 2017 at 11:28:40AM +0200, Leon Romanovsky wrote:
> > > On Mon, Jan 16, 2017 at 10:16:43AM +0100, Borislav Petkov wrote:
> > > > From: Borislav Petkov <bp@suse.de>
> > > >
> > > > We wanna know who's doing such a thing. Like slab.c does that.
> > > >
> > > > Signed-off-by: Borislav Petkov <bp@suse.de>
> > > > ---
> > > > mm/slub.c | 1 +
> > > > 1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/mm/slub.c b/mm/slub.c
> > > > index 067598a00849..1b0fa7625d6d 100644
> > > > --- a/mm/slub.c
> > > > +++ b/mm/slub.c
> > > > @@ -1623,6 +1623,7 @@ static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
> > > > flags &= ~GFP_SLAB_BUG_MASK;
> > > > pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
> > > > invalid_mask, &invalid_mask, flags, &flags);
> > > > + dump_stack();
> > >
> > > Will it make sense to change these two lines above to WARN(true, .....)?
> >
> > Should be equivalent.
>
> Almost, except one point - pr_warn and dump_stack have different log
> levels. There is a chance that user won't see pr_warn message above, but
> dump_stack will be always present.
>
> For WARN_XXX, users will always see message and stack at the same time.
On the other hand WARN* will taint the kernel and this sounds a bit
overreacting for something like a wrong gfp mask which is perfectly
recoverable. Not to mention users who care configured to panic on
warning.
So while I do not have a strong opinion on this I would rather stay with
the dump_stack.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-01-16 9:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-16 9:16 [PATCH] mm/slub: Add a dump_stack() to the unexpected GFP check Borislav Petkov
2017-01-16 9:28 ` Leon Romanovsky
2017-01-16 9:37 ` Borislav Petkov
2017-01-16 9:48 ` Leon Romanovsky
2017-01-16 9:55 ` Borislav Petkov
2017-01-16 10:09 ` Leon Romanovsky
2017-01-16 10:13 ` Borislav Petkov
2017-01-16 10:18 ` Leon Romanovsky
2017-01-16 9:59 ` Michal Hocko [this message]
2017-01-16 9:38 ` Michal Hocko
2017-01-16 10:08 ` Vlastimil Babka
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