linux-kernel - Re: [PATCH] driver core: check bus->match without holding device lock(v2)

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Date:	Wed, 21 Jan 2009 16:59:41 +0100
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	tom.leiming@...il.com
Cc:	kay.sievers@...y.org, greg@...ah.com, linux-kernel@...r.kernel.org,
	arjan@...ux.intel.com, Ming Lei <tom.leiming@...il.com>
Subject: Re: [PATCH] driver core: check bus->match without holding device
 lock(v2)

On Wed, 21 Jan 2009 23:27:47 +0800,
tom.leiming@...il.com wrote:

> From: Ming Lei <tom.leiming@...il.com>
> 
> This patch moves bus->match out from driver_probe_device and
> does not hold device lock to check the match between a device
> and a driver.
> 
> The idea has been verified by the commit 6cd495860901,
> which leads to a faster boot. But the commit 6cd495860901 has
> the following drawbacks: 1),only does the quick check in
> the path of __driver_attach->driver_probe_device, not in other
> paths; 2),for a matched device and driver, check the same match
> twice. It is a waste of cpu ,especially for some drivers with long
> device id table (eg. usb-storage driver).
> 
> This patch adds a helper of driver_match_device to check the match
> in all paths, and testes the match only once.
> 
> Signed-off-by: Ming Lei <tom.leiming@...il.com>
> ---
>  drivers/base/base.h |    5 +++++
>  drivers/base/bus.c  |    2 +-
>  drivers/base/dd.c   |   19 +++++++------------
>  3 files changed, 13 insertions(+), 13 deletions(-)

The patch looks fine to me, and it seems to work well on my s390 LPAR.

Acked-by: Cornelia Huck <cornelia.huck@...ibm.com>
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