New subject: [PATCH 2/2] drm/syncobj: Lookup the syncobj with RCU protection

2 Aug 2019

Prior to making the syncobj lookup lockless, update the idr to the new
XArray API.
Based on a patch by Matthew Wilcox willy@infradead.org
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk
---
 drivers/gpu/drm/drm_syncobj.c | 64 ++++++++++-------------------------
 include/drm/drm_file.h        |  7 ++--
 2 files changed, 21 insertions(+), 50 deletions(-)

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 1438dcb3ebb1..4fc71dc9fc43 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -86,14 +86,13 @@ struct drm_syncobj *drm_syncobj_find(struct drm_file *file_private,
 {
    struct drm_syncobj *syncobj;
-	spin_lock(&file_private->syncobj_table_lock);
+	xa_lock(&file_private->syncobjs);
-	/* Check if we currently have a reference on the object */
-	syncobj = idr_find(&file_private->syncobj_idr, handle);
+	syncobj = xa_load(&file_private->syncobjs, handle);
    if (syncobj)
    	drm_syncobj_get(syncobj);
-	spin_unlock(&file_private->syncobj_table_lock);
+	xa_unlock(&file_private->syncobjs);
return syncobj;
 }
@@ -366,23 +365,14 @@ int drm_syncobj_get_handle(struct drm_file *file_private,
 {
    int ret;
-	/* take a reference to put in the idr */
    drm_syncobj_get(syncobj);
-	idr_preload(GFP_KERNEL);
-	spin_lock(&file_private->syncobj_table_lock);
-	ret = idr_alloc(&file_private->syncobj_idr, syncobj, 1, 0, GFP_NOWAIT);
-	spin_unlock(&file_private->syncobj_table_lock);
-
-	idr_preload_end();
-
-	if (ret < 0) {
+	ret = xa_alloc(&file_private->syncobjs, handle, syncobj,
+		       xa_limit_32b, GFP_KERNEL);
+	if (ret < 0)
    	drm_syncobj_put(syncobj);
-		return ret;
-	}
-	*handle = ret;
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL(drm_syncobj_get_handle);
@@ -406,10 +396,7 @@ static int drm_syncobj_destroy(struct drm_file *file_private,
 {
    struct drm_syncobj *syncobj;
-	spin_lock(&file_private->syncobj_table_lock);
-	syncobj = idr_remove(&file_private->syncobj_idr, handle);
-	spin_unlock(&file_private->syncobj_table_lock);
-
+	syncobj = xa_erase(&file_private->syncobjs, handle);
    if (!syncobj)
    	return -EINVAL;
@@ -492,20 +479,12 @@ static int drm_syncobj_fd_to_handle(struct drm_file *file_private,
    	return -EINVAL;
    }
-	/* take a reference to put in the idr */
    syncobj = f.file->private_data;
    drm_syncobj_get(syncobj);
-	idr_preload(GFP_KERNEL);
-	spin_lock(&file_private->syncobj_table_lock);
-	ret = idr_alloc(&file_private->syncobj_idr, syncobj, 1, 0, GFP_NOWAIT);
-	spin_unlock(&file_private->syncobj_table_lock);
-	idr_preload_end();
-
-	if (ret > 0) {
-		*handle = ret;
-		ret = 0;
-	} else
+	ret = xa_alloc(&file_private->syncobjs, handle, syncobj,
+		       xa_limit_32b, GFP_KERNEL);
+	if (ret < 0)
    	drm_syncobj_put(syncobj);
fdput(f);
@@ -575,17 +554,7 @@ static int drm_syncobj_export_sync_file(struct drm_file *file_private,
 void
 drm_syncobj_open(struct drm_file *file_private)
 {
-	idr_init_base(&file_private->syncobj_idr, 1);
-	spin_lock_init(&file_private->syncobj_table_lock);
-}
-
-static int
-drm_syncobj_release_handle(int id, void *ptr, void *data)
-{
-	struct drm_syncobj *syncobj = ptr;
-
-	drm_syncobj_put(syncobj);
-	return 0;
+	xa_init_flags(&file_private->syncobjs, XA_FLAGS_ALLOC1);
 }
/**
@@ -599,9 +568,12 @@ drm_syncobj_release_handle(int id, void *ptr, void *data)
 void
 drm_syncobj_release(struct drm_file *file_private)
 {
-	idr_for_each(&file_private->syncobj_idr,
-		     &drm_syncobj_release_handle, file_private);
-	idr_destroy(&file_private->syncobj_idr);
+	struct drm_syncobj *syncobj;
+	unsigned long index;
+
+	xa_for_each(&file_private->syncobjs, index, syncobj)
+		drm_syncobj_put(syncobj);
+	xa_destroy(&file_private->syncobjs);
 }
int
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 67af60bb527a..c6efb5f83fcf 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -33,6 +33,7 @@
 #include <linux/types.h>
 #include <linux/completion.h>
 #include <linux/idr.h>
+#include <linux/xarray.h>
#include <uapi/drm/drm.h>
@@ -251,10 +252,8 @@ struct drm_file {
    /** @table_lock: Protects @object_idr. */
    spinlock_t table_lock;
-	/** @syncobj_idr: Mapping of sync object handles to object pointers. */
-	struct idr syncobj_idr;
-	/** @syncobj_table_lock: Protects @syncobj_idr. */
-	spinlock_t syncobj_table_lock;
+	/** @syncobjs: Mapping of sync object handles to object pointers. */
+	struct xarray syncobjs;
/** @filp: Pointer to the core file structure. */
    struct file *filp;
-- 
2.23.0.rc0


    

[PATCH 1/2] drm/syncobj: Convert syncobj_idr to XArray