From: Hyunmin Lee <hn.min.lee@gmail.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Uladzislau Rezki <urezki@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>,
Jeungwoo Yoo <casionwoo@gmail.com>,
Sangyun Kim <sangyun.kim@snu.ac.kr>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>
Subject: Re: [PATCH] replace BUG_ON to WARN_ON
Date: Tue, 31 Jan 2023 19:56:29 +0900 [thread overview]
Message-ID: <20230131105629.GA1195431@min-iamroot> (raw)
In-Reply-To: <Y9eYbPuq5Nw9Njxf@kernel.org>
On Mon, Jan 30, 2023 at 12:14:04PM +0200, Mike Rapoport wrote:
> Hi,
>
> On Fri, Jan 27, 2023 at 08:58:44PM +0900, Hyunmin Lee wrote:
> > Replace unnacessary BUG_ON to WARN_ON. These BUG_ONs verify aruguments of a function. Thus, the WARN_ONs return an EINVAL error when their condition is true.
>
> Some users enable panic_on_warn, so for them WARN_ON will still crash a
> machine.
>
> I think a simple if() will be sufficient.
>
> > Co-Developed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> > Co-Developed-by: Jeungwoo Yoo <casionwoo@gmail.com>
> > Co-Developed-by: Sangyun Kim <sangyun.kim@snu.ac.kr>
> > Signed-off-by: Hyunmin Lee <hn.min.lee@gmail.com>
> > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> > Signed-off-by: Jeungwoo Yoo <casionwoo@gmail.com>
> > Signed-off-by: Sangyun Kim <sangyun.kim@snu.ac.kr>
> > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> > ---
> > mm/vmalloc.c | 11 ++++++++---
> > 1 file changed, 8 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 74afa2208558..9f9dba3132c5 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -1587,9 +1587,14 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> > int purged = 0;
> > int ret;
> >
> > - BUG_ON(!size);
> > - BUG_ON(offset_in_page(size));
> > - BUG_ON(!is_power_of_2(align));
> > + if (WARN_ON(!size))
> > + return ERR_PTR(-EINVAL);
> > +
> > + if (WARN_ON(offset_in_page(size)))
> > + return ERR_PTR(-EINVAL);
> > +
> > + if (WARN_ON(!is_power_of_2(align)))
> > + return ERR_PTR(-EINVAL);
> >
> > if (unlikely(!vmap_initialized))
> > return ERR_PTR(-EBUSY);
> > --
> > 2.25.1
> >
> >
>
> --
> Sincerely yours,
> Mike.
Hi Mike,
Thank you for your advice.
Would you please give feedback about the below opinion?
- Printing warning messages is helpful to inform what happened in the system to the users.
- When a simple if() is used instead of WARN_ON, the if() should print a warning message.
- The condition of the simple if() should also have unlikely() for optimization of system performance.
- WARN_ON is a macro doing like thoes easily. It has a notifying function and unlikely optimization.
- Eventhough WARN_ON will still crash like BUG_ON by some users who enable panic_on_warn, it is their intention. They should accept the crash by WARN_ON.
- Therefore, using WARN_ON looks like natural and efficient.
Best,
Hyunmin
next prev parent reply other threads:[~2023-01-31 10:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-27 11:58 [PATCH] replace BUG_ON to WARN_ON Hyunmin Lee
2023-01-27 15:03 ` Hyeonggon Yoo
2023-01-30 10:14 ` Mike Rapoport
2023-01-31 10:56 ` Hyunmin Lee [this message]
2023-01-31 13:47 ` Mike Rapoport
2023-02-01 10:03 ` Hyunmin Lee
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