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From: "Noralf Trønnes" <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
To: dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org
Cc: David1.Zhou-5C7GfCeVMHo@public.gmane.org,
	Andrey.Grodzovsky-5C7GfCeVMHo@public.gmane.org,
	oleksandr_andrushchenko-uRwfk40T5oI@public.gmane.org,
	daniel.vetter-/w4YWyX8dFk@public.gmane.org,
	intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	amd-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	"Noralf Trønnes" <noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>,
	alexander.deucher-5C7GfCeVMHo@public.gmane.org,
	airlied-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
	sean-p7yTbzM4H96eqtR555YLDQ@public.gmane.org,
	christian.koenig-5C7GfCeVMHo@public.gmane.org
Subject: [PATCH v2 1/2] drm: Fix drm_release() and device unplug
Date: Fri,  8 Feb 2019 15:01:02 +0100	[thread overview]
Message-ID: <20190208140103.28919-2-noralf@tronnes.org> (raw)
In-Reply-To: <20190208140103.28919-1-noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>

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>
---
 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 381581b01d48..05bbc2b622fc 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -376,11 +376,7 @@ 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);
-- 
2.20.1

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  parent reply	other threads:[~2019-02-08 14:01 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08 14:01 [PATCH v2 0/2] drm/drv: Rework drm_dev_unplug() (was: Remove drm_dev_unplug()) Noralf Trønnes
     [not found] ` <20190208140103.28919-1-noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
2019-02-08 14:01   ` Noralf Trønnes [this message]
2019-02-08 14:01   ` [PATCH v2 2/2] drm/drv: drm_dev_unplug(): Move out drm_dev_put() call Noralf Trønnes
2019-02-08 14:36     ` Oleksandr Andrushchenko
     [not found]     ` <20190208140103.28919-3-noralf-L59+Z2yzLopAfugRpC6u6w@public.gmane.org>
2019-02-11  8:28       ` Daniel Vetter
2019-02-08 15:54 ` ✓ Fi.CI.BAT: success for drm/drv: Rework drm_dev_unplug() (was: Remove drm_dev_unplug()) Patchwork
2019-02-08 18:45 ` ✓ Fi.CI.IGT: " Patchwork
2019-02-21 11:31 ` [PATCH v2 0/2] " Noralf Trønnes

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