| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20090120152108.032405b2@gondolin>
Date: Tue, 20 Jan 2009 15:21:08 +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
On Tue, 20 Jan 2009 21:34:08 +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).
I agree with the goal of that patch, as it essentially cleanly
seperates the quick check (->match) from the deeper probing (->probe).
>
> 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/bus.c | 8 +++++++-
> drivers/base/dd.c | 19 +++++++------------
> include/linux/device.h | 6 ++++++
> 3 files changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index 83f32b8..c570d16 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -199,6 +199,12 @@ static ssize_t driver_bind(struct device_driver *drv,
>
> dev = bus_find_device_by_name(bus, NULL, buf);
> if (dev && dev->driver == NULL) {
> +
> + if (!driver_match_device(drv, dev)) {
> + err = 0;
> + goto not_match;
> + }
> +
This looks too complicated, I'd just change the if to
if (dev && dev->driver == NULL && driver_match_device(drv,dev))
> if (dev->parent) /* Needed for USB */
> down(&dev->parent->sem);
> down(&dev->sem);
> @@ -206,7 +212,7 @@ static ssize_t driver_bind(struct device_driver *drv,
> up(&dev->sem);
> if (dev->parent)
> up(&dev->parent->sem);
> -
> +not_match:
> if (err > 0) {
> /* success */
> err = count;
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 315bed8..61f32db 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -172,14 +172,8 @@ int driver_probe_done(void)
> * @drv: driver to bind a device to
> * @dev: device to try to bind to the driver
> *
> - * First, we call the bus's match function, if one present, which should
> - * compare the device IDs the driver supports with the device IDs of the
> - * device. Note we don't do this ourselves because we don't know the
> - * format of the ID structures, nor what is to be considered a match and
> - * what is not.
> - *
> - * This function returns 1 if a match is found, -ENODEV if the device is
> - * not registered, and 0 otherwise.
> + * This function returns -ENODEV if the device is not registered,
> + * and 0 otherwise.
This is incorrect, really_probe() still returns 1 if the device could
be bound.
> *
> * This function must be called with @dev->sem held. When called for a
> * USB interface, @dev->parent->sem must be held as well.
> @@ -190,21 +184,22 @@ int driver_probe_device(struct device_driver *drv, struct device *dev)
>
> if (!device_is_registered(dev))
> return -ENODEV;
> - if (drv->bus->match && !drv->bus->match(dev, drv))
> - goto done;
>
> pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
> drv->bus->name, __func__, dev_name(dev), drv->name);
>
> ret = really_probe(dev, drv);
>
> -done:
> return ret;
> }
>
> static int __device_attach(struct device_driver *drv, void *data)
> {
> struct device *dev = data;
> +
> + if (!driver_match_device(drv, dev))
> + return 0;
> +
> return driver_probe_device(drv, dev);
> }
>
> @@ -257,7 +252,7 @@ static int __driver_attach(struct device *dev, void *data)
> * is an error.
> */
>
> - if (drv->bus->match && !drv->bus->match(dev, drv))
> + if (!driver_match_device(drv, dev))
> return 0;
>
> if (dev->parent) /* Needed for USB */
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 45e5b19..3c61315 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -466,6 +466,12 @@ static inline int device_is_registered(struct device *dev)
> return dev->kobj.state_in_sysfs;
> }
>
> +static inline int driver_match_device(struct device_driver *drv,
> + struct device *dev)
> +{
> + return drv->bus->match && drv->bus->match(dev, drv);
> +}
> +
This should go into drivers/base/base.h instead, as no code outside the
driver core should use it.
> void driver_init(void);
>
> /*
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists