| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.0 059/101] drm: Fix drm_release() and device unplug | Date | Thu, 2 May 2019 17:21:01 +0200 |
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[ Upstream commit 3f04e0a6cfebf48152ac64502346cdc258811f79 ]
If userspace has open fd(s) when drm_dev_unplug() is run, it will result in drm_dev_unregister() being called twice. First in drm_dev_unplug() and then later in drm_release() through the call to drm_put_dev().
Since userspace already holds a ref on drm_device through the drm_minor, it's not necessary to add extra ref counting based on no open file handles. Instead just drm_dev_put() unconditionally in drm_dev_unplug().
We now have this: - Userpace holds a ref on drm_device as long as there's open fd(s) - The driver holds a ref on drm_device as long as it's bound to the struct device
When both sides are done with drm_device, it is released.
Signed-off-by: Noralf Trønnes <noralf@tronnes.org> Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Reviewed-by: Sean Paul <sean@poorly.run> Signed-off-by: Dave Airlie <airlied@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190208140103.28919-2-noralf@tronnes.org Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org> --- drivers/gpu/drm/drm_drv.c | 6 +----- drivers/gpu/drm/drm_file.c | 6 ++---- 2 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 12e5e2be7890..7a59b8b3ed5a 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -381,11 +381,7 @@ void drm_dev_unplug(struct drm_device *dev) synchronize_srcu(&drm_unplug_srcu); drm_dev_unregister(dev); - - mutex_lock(&drm_global_mutex); - if (dev->open_count == 0) - drm_dev_put(dev); - mutex_unlock(&drm_global_mutex); + drm_dev_put(dev); } EXPORT_SYMBOL(drm_dev_unplug); diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index 46f48f245eb5..3f20f598cd7c 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -479,11 +479,9 @@ int drm_release(struct inode *inode, struct file *filp) drm_file_free(file_priv); - if (!--dev->open_count) { + if (!--dev->open_count) drm_lastclose(dev); - if (drm_dev_is_unplugged(dev)) - drm_put_dev(dev); - } + mutex_unlock(&drm_global_mutex); drm_minor_release(minor); -- 2.19.1
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