Messages in this thread Patch in this message | | | Date | Tue, 27 Jun 2023 18:20:18 +0800 | Subject | Re: [PATCH] drm: Remove the deprecated drm_put_dev() function | From | Sui Jingfeng <> |
| |
Hi,
On 2023/6/27 17:33, Jani Nikula wrote: > On Tue, 27 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote: >> Hi, >> >> On 2023/6/26 15:48, Jani Nikula wrote: >>> On Sun, 25 Jun 2023, Sui Jingfeng <suijingfeng@loongson.cn> wrote: >>>> As this function can be replaced with drm_dev_unregister() + drm_dev_put(), >>>> it is already marked as deprecated, so remove it. No functional change. >>>> >>>> Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn> >>>> --- >>>> drivers/gpu/drm/drm_drv.c | 28 ---------------------------- >>>> drivers/gpu/drm/drm_pci.c | 3 ++- >>>> drivers/gpu/drm/radeon/radeon_drv.c | 3 ++- >>>> include/drm/drm_drv.h | 1 - >>>> 4 files changed, 4 insertions(+), 31 deletions(-) >>>> >>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c >>>> index 12687dd9e1ac..5057307fe22a 100644 >>>> --- a/drivers/gpu/drm/drm_drv.c >>>> +++ b/drivers/gpu/drm/drm_drv.c >>>> @@ -406,34 +406,6 @@ void drm_minor_release(struct drm_minor *minor) >>>> * possibly leaving the hardware enabled. >>>> */ >>>> >>>> -/** >>>> - * drm_put_dev - Unregister and release a DRM device >>>> - * @dev: DRM device >>>> - * >>>> - * Called at module unload time or when a PCI device is unplugged. >>>> - * >>>> - * Cleans up all DRM device, calling drm_lastclose(). >>>> - * >>>> - * Note: Use of this function is deprecated. It will eventually go away >>>> - * completely. Please use drm_dev_unregister() and drm_dev_put() explicitly >>>> - * instead to make sure that the device isn't userspace accessible any more >>>> - * while teardown is in progress, ensuring that userspace can't access an >>>> - * inconsistent state. >>> The last sentence is the crucial one. While the patch has no functional >>> changes, >> But my patch help to save a useless check(if (!dev)) >> >> on where we found the check is not necessary. >> >> ``` >> >> - if (!dev) { >> - DRM_ERROR("cleanup called no dev\n"); >> - return; >> - } >> >> ``` >> >> >>> I believe the goal never was to just mechanically replace one >>> call with the two. >> The DRM core lose nothing, just a function wrapper. >> >> Instead, this is probably a good chance to migrate the burden to the >> driver side. > The point is to *fix* this stuff while doing the conversion. Anyone can > replace one function call with two, but that's just brushing the problem > under the carpet.
Interesting!
To be honest, I love you reviews.
I think, I probably be able to solve more practical problem,
This patch is just a trivial, I don't care much.
Can you help to have a look at my vgaarb patch set [1]
[1] https://patchwork.freedesktop.org/series/119250/
Really need you guidance there.
> The current state is that we have a function the use of which is > potentially problematic, it's documented, and we can trivially locate > all the call sites.
I can merge the document to comments of the drm_dev_unregister() function,
remove the drm_put_dev function only. What do you think about this?
> After your change, we've lost that information, and we haven't fixed > anything. > My understanding is that drm_dev_unregister() alone is enough to stop the user-space
program accessing the kernel interface exposed.
```
radeon_pci_remove(struct pci_dev *pdev)
{
// should be called first in the pci remove funcition
drm_dev_unregister(dev);
// do the various(necessary) cleanup and free resource allocated
// call this function at the bottom of the radeon_pci_remove() function
drm_dev_put(dev);
}
```
And the drm_dev_unregister() function already told us, see below:
``` /** * drm_dev_unregister - Unregister DRM device * @dev: Device to unregister * * Unregister the DRM device from the system. This does the reverse of * drm_dev_register() but does not deallocate the device. The caller must call * drm_dev_put() to drop their final reference, unless it is managed with devres * (as devices allocated with devm_drm_dev_alloc() are), in which case there is * already an unwind action registered. * * A special form of unregistering for hotpluggable devices is drm_dev_unplug(), * which can be called while there are still open users of @dev. * * This should be called first in the device teardown code to make sure * userspace can't access the device instance any more. */ void drm_dev_unregister(struct drm_device *dev)
...
```
Thanks for the interesting remark again.
> BR, > Jani. > > >> I think the device driver(drm/radeon, for example) have better understanding >> >> about how to ensure that userspace can't access an inconsistent state >> than the DRM core. >> >>> BR, >>> Jani. >>> >>> >>>> - */ >>>> -void drm_put_dev(struct drm_device *dev) >>>> -{ >>>> - DRM_DEBUG("\n"); >>>> - >>>> - if (!dev) { >>>> - DRM_ERROR("cleanup called no dev\n"); >>>> - return; >>>> - } >>>> - >>>> - drm_dev_unregister(dev); >>>> - drm_dev_put(dev); >>>> -} >>>> -EXPORT_SYMBOL(drm_put_dev); >>>> - >>>> /** >>>> * drm_dev_enter - Enter device critical section >>>> * @dev: DRM device >>>> diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c >>>> index 39d35fc3a43b..b3a68a92eaa6 100644 >>>> --- a/drivers/gpu/drm/drm_pci.c >>>> +++ b/drivers/gpu/drm/drm_pci.c >>>> @@ -257,7 +257,8 @@ void drm_legacy_pci_exit(const struct drm_driver *driver, >>>> legacy_dev_list) { >>>> if (dev->driver == driver) { >>>> list_del(&dev->legacy_dev_list); >>>> - drm_put_dev(dev); >>>> + drm_dev_unregister(dev); >>>> + drm_dev_put(dev); >>>> } >>>> } >>>> mutex_unlock(&legacy_dev_list_lock); >>>> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c >>>> index e4374814f0ef..a4955ae10659 100644 >>>> --- a/drivers/gpu/drm/radeon/radeon_drv.c >>>> +++ b/drivers/gpu/drm/radeon/radeon_drv.c >>>> @@ -357,7 +357,8 @@ radeon_pci_remove(struct pci_dev *pdev) >>>> { >>>> struct drm_device *dev = pci_get_drvdata(pdev); >>>> >>>> - drm_put_dev(dev); >>>> + drm_dev_unregister(dev); >>>> + drm_dev_put(dev); >>>> } >>>> >>>> static void >>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h >>>> index 89e2706cac56..289c97b12e82 100644 >>>> --- a/include/drm/drm_drv.h >>>> +++ b/include/drm/drm_drv.h >>>> @@ -511,7 +511,6 @@ void drm_dev_unregister(struct drm_device *dev); >>>> >>>> void drm_dev_get(struct drm_device *dev); >>>> void drm_dev_put(struct drm_device *dev); >>>> -void drm_put_dev(struct drm_device *dev); >>>> bool drm_dev_enter(struct drm_device *dev, int *idx); >>>> void drm_dev_exit(int idx); >>>> void drm_dev_unplug(struct drm_device *dev);
-- Jingfeng
| |