linux-kernel - Re: [BUG Fix Patch 1/6] Bug fix: Hold spinlock across find|remove /sys/firmware/memmap/X operation.

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Message-ID: <CAGRGNgWCdvWhp=9+PDRbC9bK100BdBv9kpcsqoM-J6ipq22Szw@mail.gmail.com>
Date:	Wed, 16 Jan 2013 09:26:49 +1100
From:	Julian Calaby <julian.calaby@...il.com>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	akpm@...ux-foundation.org, rientjes@...gle.com,
	len.brown@...el.com, benh@...nel.crashing.org, paulus@...ba.org,
	cl@...ux.com, minchan.kim@...il.com,
	kosaki.motohiro@...fujitsu.com, isimatu.yasuaki@...fujitsu.com,
	wujianguo@...wei.com, wency@...fujitsu.com, hpa@...or.com,
	linfeng@...fujitsu.com, laijs@...fujitsu.com, mgorman@...e.de,
	yinghai@...nel.org, glommer@...allels.com, jiang.liu@...wei.com,
	x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-ia64@...r.kernel.org, cmetcalf@...era.com,
	sparclinux@...r.kernel.org
Subject: Re: [BUG Fix Patch 1/6] Bug fix: Hold spinlock across find|remove
 /sys/firmware/memmap/X operation.

Hi Tang,

One minor point.

On Tue, Jan 15, 2013 at 9:54 PM, Tang Chen <tangchen@...fujitsu.com> wrote:
> It is unsafe to return an entry pointer and release the map_entries_lock. So we should
> not hold the map_entries_lock separately in firmware_map_find_entry() and
> firmware_map_remove_entry(). Hold the map_entries_lock across find and remove
> /sys/firmware/memmap/X operation.
>
> And also, users of these two functions need to be careful to hold the lock when using
> these two functions.
>
> The suggestion is from Andrew Morton <akpm@...ux-foundation.org>
>
> Signed-off-by: Tang Chen <tangchen@...fujitsu.com>
> ---
>  drivers/firmware/memmap.c |   25 +++++++++++++++++--------
>  1 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/firmware/memmap.c b/drivers/firmware/memmap.c
> index 4211da5..940c4e9 100644
> --- a/drivers/firmware/memmap.c
> +++ b/drivers/firmware/memmap.c
> @@ -188,23 +188,28 @@ static inline void remove_sysfs_fw_map_entry(struct firmware_map_entry *entry)
>  }
>
>  /*
> - * Search memmap entry
> + * firmware_map_find_entry: Search memmap entry.
> + * @start: Start of the memory range.
> + * @end:   End of the memory range (exclusive).
> + * @type:  Type of the memory range.
> + *
> + * This function is to find the memmap entey of a given memory range.
> + * The caller must hold map_entries_lock, and must not release the lock
> + * until the processing of the returned entry has completed.
> + *
> + * Return pointer to the entry to be found on success, or NULL on failure.

Why not make this completely kernel-doc compliant as you're already
re-writing the comment?

Thanks,

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/
.Plan: http://sites.google.com/site/juliancalaby/
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