Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   =?UTF-8?q?Micha=C5=82=20Winiarski?= <michal.winiarski@intel.com>
To:     <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>
CC:     David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
        "Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Simon Ser <contact@emersion.fr>,
        Matthew Wilcox <willy@infradead.org>,
        =?UTF-8?q?Micha=C5=82=20Winiarski?= <michal.winiarski@intel.com>,
        "Daniel Vetter" <daniel.vetter@ffwll.ch>
Subject: [PATCH v3 3/4] drm: Use mutex for minors
Date:   Tue, 6 Sep 2022 16:01:16 +0200
Message-ID: <20220906140117.409852-4-michal.winiarski@intel.com>
In-Reply-To: <20220906140117.409852-1-michal.winiarski@intel.com>
References: <20220906140117.409852-1-michal.winiarski@intel.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?V3V4TDBjd3dEeWtOenFlQlNleG1aNmMxazJXcmpUV1hVczdGai9MTmlWc1RC?=
 =?utf-8?B?VC9Rdk0ySm95SlppdWhmVjJwSkJ0cG9zNWZ0RUVkS3p2TlBWL21pYWhXc3lR?=
 =?utf-8?B?WlZ5TEJEbStCSGJnSS9qRnozc1ZkUE9LNDB4RXd2SFh4eWo0MkdIVW9NNmVK?=
 =?utf-8?B?ZXZXWkx4QzM5VE5LVm5BeER0Z0R3aFNRRjZhQlhmMFQrWW1nVHUrcWwrYjZB?=
 =?utf-8?B?VFlpKy9Fc3M0TklhWUNqMmFUaXl5WlJMSkNzWlhvSUpHamJxb0RRU1AzelFP?=
 =?utf-8?B?NGJNWm9xTXdrMmM4L1VaRTB4NVFaeXhrdXd0OXZMY3AwR0dBOUIvMisvTzIx?=
 =?utf-8?B?R015bzRsYWxscm52N25DQThlcCtFSFNSdEdtbnRMM0RXb0xiZks4UmtLQXpy?=
 =?utf-8?B?cU5kYVpTdTl0U1pJQ0d2ZHdEUjd5bzU1OVlZU0Q0dWhGY3AvSUlGQjRNb244?=
 =?utf-8?B?OVVndGVEVWxhSFkwVUtmNDRYS0NoeXA3cU9NWjNEakdaUDdMMS9tUnhyZ3cv?=
 =?utf-8?B?Y1FOOC9qeFpQdjhKOUJGSE5OT0VGUjJyejlvZll1OHFaZE9oR1dkSGMrYlhZ?=
 =?utf-8?B?MXAvSGJFQ1NpS0RmVkZnbit2MnRpV2Q3M243R2QvNndyMnBsUkZsekd3WjRa?=
 =?utf-8?B?am1CWnNOUXpHM3R4V1I0ekJMTFlvVVFoYVljYjdvUjJWSGY0SWg0djFSVHBh?=
 =?utf-8?B?bk9FKzRzVXJyeUpUNGxKWjBuajM4QVdzMDFJVkRSYU1wMTdRT2hvZEtISThV?=
 =?utf-8?B?d2p1Zi9sYmp1NzI5a093amZBYU5VN2VzU1BJWFNSOHpRWHVZOGxUbVYydmNG?=
 =?utf-8?B?TGcrcVdmaktpWmxLYURVckdxYitxRmhNL1Z0TG5WL2RoWHpvdzFJNHQrODhL?=
 =?utf-8?B?RDhYQ3BKZk5sV3lTMWUyZEhnVTRFS050NWFZT2h2ZWNPRGlseWNpU2hnQmI3?=
 =?utf-8?B?OGR2SW5qOGFMZ3cwdGFEV3RzaVZVWDN5YS9IVndmV2laY2NoU0lDQkx3SnZ1?=
 =?utf-8?B?aDlmbldWcG5VSklTbVN2UmtlY1ZMYkgwSWNZaUtxUERFbFB0SCtIdnpVU010?=
 =?utf-8?B?RkFhSGJYSndtNWkweXZaQSt3WWlCY2JtU0V3aGJNTUwyNEhFdjhJeWlUWG1M?=
 =?utf-8?B?TXZYblFnWWJLZFRwQlNyRi9OdDVPeGFKbFozc3JZMFkzMjFwbFQ4U0l3RXJR?=
 =?utf-8?B?b3Z5dHNTOTlkelpVaXpLcHZHZkpSUVpha243L0NMcnhpZEtEekcvenhvZGtm?=
 =?utf-8?B?dTZJclp5a2xIbnJUWWEvUkFZVDFNMmNRZ2I5NFhCbWdaMTdRK0dsT3hYQnh5?=
 =?utf-8?B?TG1MOTZRdC9CT2JuWWd6WkNlVDhldTBHaXdVRVpkdjB1NFlCMCtVVkhQdUk0?=
 =?utf-8?B?UmI2aUFISFQ0WGpoN0JsNUFxSFcrTmFoT0FTREFXSUpwcm9pOGxRRjNhVVlX?=
 =?utf-8?B?a1paNnRacmFUa1pkVEhhRWlSaE9WY1RWS0lZOGk3bFRBVnR6TEFXaXhUSE1I?=
 =?utf-8?B?ZWdMVmI1YlE5MTRTN0pWU1RmeFMyTVJtM3ArT21zeVFqRzVLZHNrc2N4bDJB?=
 =?utf-8?B?YUdBRTgrNHlGaWpsQVhIQktvRitaellBZmQ3RHJoWmlWUml2YUVFZUF0MHhC?=
 =?utf-8?B?OExzcjc4MWhtazhXV3NocUttYitxQWI0UWRzYU5Xb0pwSUw4eWNoRkpwNzlt?=
 =?utf-8?B?QStNdEdCZGVNNzV0UEJnZlJ5N1Evb2Z3TDV3bEpJN2dCM0VCdUY4SHVNNysv?=
 =?utf-8?B?SzZMenIrWDFwUHFSeThtdEZwTURXeWZEOEdZMW9TQjFHeWdpZjR4YUhSZWlE?=
 =?utf-8?B?Q055TzdpMDYzcXdXVEVIZHpMT1lmZ1l1QjNlVExDc3IwWHEvazZZWCs4aWd4?=
 =?utf-8?B?L2gyc011R3ZFdjB6eXgxZnNSanJsT3NCRDloSHhsbVpXZGpXTUl6WGZab0Mz?=
 =?utf-8?B?clhQbjJMNGZuMncxcWpJSWFUK0N6WlU4NmdnTXJEYVQ5bFNEV3pVNEtPY1gv?=
 =?utf-8?B?cTdheW5qemVqd05ua0FRT0NJUm1mNmJMeU5ZclVrZi9xT1hhcnIySTFVWkw5?=
 =?utf-8?B?SWZIdS9qdnA4VHlVTFltQTBxY3NuYnR6MHl2SmgzMTNsSzhXMEtzWlNzdjNn?=
 =?utf-8?B?bzUxWGxXRDdwMUZzNjM0c2ZObGZRSVhCVCtra1ZPTitXL3VwZS9Wemo3WUVD?=
 =?utf-8?B?UEE9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: bdce2cd5-bebb-4d0d-1022-08da90105f38
X-MS-Exchange-CrossTenant-AuthSource: DM4PR11MB5373.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Sep 2022 14:02:01.8982
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: uptTkggN357Kt71bfS2a6HsX++2u8iD0GFBP0I4hzx4wCKB9DQzheRVHNjWim4uaqwMMSm9yCrh3ixAzgwq8+AtkhCbJ7gcHN8JKwfRDxM0=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN7PR11MB2804
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,
        RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,
        T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Operating on drm minor is not done in IRQ context, which means that we
could safely downgrade to regular non-irq spinlock.
But we can also go further and drop the idr_preload tricks by just using
a mutex.

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/drm_drv.c | 33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 0bdcca0db611..f66904527256 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -53,7 +53,7 @@ MODULE_AUTHOR("Gareth Hughes, Leif Delgass, José Fonseca, Jon Smirl");
 MODULE_DESCRIPTION("DRM shared core routines");
 MODULE_LICENSE("GPL and additional rights");
 
-static DEFINE_SPINLOCK(drm_minor_lock);
+static DEFINE_MUTEX(drm_minor_lock);
 static struct idr drm_minors_idr;
 
 static bool skip_legacy_minors;
@@ -103,21 +103,19 @@ static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,
 static void drm_minor_alloc_release(struct drm_device *dev, void *data)
 {
 	struct drm_minor *minor = data;
-	unsigned long flags;
 
 	WARN_ON(dev != minor->dev);
 
 	put_device(minor->kdev);
 
-	spin_lock_irqsave(&drm_minor_lock, flags);
+	mutex_lock(&drm_minor_lock);
 	idr_remove(&drm_minors_idr, minor->index);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	mutex_unlock(&drm_minor_lock);
 }
 
 static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 	int r = -ENOSPC;
 
 	minor = drmm_kzalloc(dev, sizeof(*minor), GFP_KERNEL);
@@ -133,18 +131,16 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 	 * and 128-191 are render nodes.
 	 * After reaching the limit, we're allocating minors dynamically - first-come, first-serve.
 	 */
-	idr_preload(GFP_KERNEL);
-	spin_lock_irqsave(&drm_minor_lock, flags);
+	mutex_lock(&drm_minor_lock);
 	if (!skip_legacy_minors)
 		r = idr_alloc(&drm_minors_idr,
 			      NULL,
 			      64 * type,
 			      64 * (type + 1),
-			      GFP_NOWAIT);
+			      GFP_KERNEL);
 	if (r == -ENOSPC)
-		r = idr_alloc(&drm_minors_idr, NULL, 192, 1 << MINORBITS, GFP_NOWAIT);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
-	idr_preload_end();
+		r = idr_alloc(&drm_minors_idr, NULL, 192, 1 << MINORBITS, GFP_KERNEL);
+	mutex_unlock(&drm_minor_lock);
 
 	if (r < 0)
 		return r;
@@ -166,7 +162,6 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 static int drm_minor_register(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 	int ret;
 
 	DRM_DEBUG("\n");
@@ -186,9 +181,9 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type)
 		goto err_debugfs;
 
 	/* replace NULL with @minor so lookups will succeed from now on */
-	spin_lock_irqsave(&drm_minor_lock, flags);
+	mutex_lock(&drm_minor_lock);
 	idr_replace(&drm_minors_idr, minor, minor->index);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	mutex_unlock(&drm_minor_lock);
 
 	DRM_DEBUG("new minor registered %d\n", minor->index);
 	return 0;
@@ -201,16 +196,15 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type)
 static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 
 	minor = *drm_minor_get_slot(dev, type);
 	if (!minor || !device_is_registered(minor->kdev))
 		return;
 
 	/* replace @minor with NULL so lookups will fail from now on */
-	spin_lock_irqsave(&drm_minor_lock, flags);
+	mutex_lock(&drm_minor_lock);
 	idr_replace(&drm_minors_idr, NULL, minor->index);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	mutex_unlock(&drm_minor_lock);
 
 	device_del(minor->kdev);
 	dev_set_drvdata(minor->kdev, NULL); /* safety belt */
@@ -229,13 +223,12 @@ static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
 struct drm_minor *drm_minor_acquire(unsigned int minor_id)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 
-	spin_lock_irqsave(&drm_minor_lock, flags);
+	mutex_lock(&drm_minor_lock);
 	minor = idr_find(&drm_minors_idr, minor_id);
 	if (minor)
 		drm_dev_get(minor->dev);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	mutex_unlock(&drm_minor_lock);
 
 	if (!minor) {
 		return ERR_PTR(-ENODEV);
-- 
2.37.3