[POWERPC] spufs: Add infrastructure needed for gang scheduling

Add the concept of a gang to spufs as a new type of object.
So far, this has no impact whatsover on scheduling, but makes
it possible to add that later.

A new type of object in spufs is now a spu_gang. It is created
with the spu_create system call with the flags argument set
to SPU_CREATE_GANG (0x2). Inside of a spu_gang, it
is then possible to create spu_context objects, which until
now was only possible at the root of spufs.

There is a new member in struct spu_context pointing to
the spu_gang it belongs to, if any. The spu_gang maintains
a list of spu_context structures that are its children.
This information can then be used in the scheduler in the
future.

There is still a bug that needs to be resolved in this
basic infrastructure regarding the order in which objects
are removed. When the spu_gang file descriptor is closed
before the spu_context descriptors, we leak the dentry
and inode for the gang. Any ideas how to cleanly solve
this are appreciated.

Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Paul Mackerras <[email protected]>

arch/powerpc/platforms/cell/spufs/Makefile

@@ -2,7 +2,7 @@ obj-y += switch.o
 
 obj-$(CONFIG_SPU_FS) += spufs.o
 spufs-y += inode.o file.o context.o syscalls.o
-spufs-y += sched.o backing_ops.o hw_ops.o run.o
+spufs-y += sched.o backing_ops.o hw_ops.o run.o gang.o
 
 # Rules to build switch.o with the help of SPU tool chain
 SPU_CROSS	:= spu-

arch/powerpc/platforms/cell/spufs/context.c

@@ -27,7 +27,7 @@
 #include <asm/spu_csa.h>
 #include "spufs.h"
 
-struct spu_context *alloc_spu_context(void)
+struct spu_context *alloc_spu_context(struct spu_gang *gang)
 {
 	struct spu_context *ctx;
 	ctx = kzalloc(sizeof *ctx, GFP_KERNEL);
@@ -51,6 +51,8 @@ struct spu_context *alloc_spu_context(void)
 	ctx->state = SPU_STATE_SAVED;
 	ctx->ops = &spu_backing_ops;
 	ctx->owner = get_task_mm(current);
+	if (gang)
+		spu_gang_add_ctx(gang, ctx);
 	goto out;
 out_free:
 	kfree(ctx);
@@ -67,6 +69,8 @@ void destroy_spu_context(struct kref *kref)
 	spu_deactivate(ctx);
 	up_write(&ctx->state_sema);
 	spu_fini_csa(&ctx->csa);
+	if (ctx->gang)
+		spu_gang_remove_ctx(ctx->gang, ctx);
 	kfree(ctx);
 }
 

arch/powerpc/platforms/cell/spufs/gang.c

@@ -0,0 +1,81 @@
+/*
+ * SPU file system
+ *
+ * (C) Copyright IBM Deutschland Entwicklung GmbH 2005
+ *
+ * Author: Arnd Bergmann <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/list.h>
+#include <linux/slab.h>
+
+#include "spufs.h"
+
+struct spu_gang *alloc_spu_gang(void)
+{
+	struct spu_gang *gang;
+
+	gang = kzalloc(sizeof *gang, GFP_KERNEL);
+	if (!gang)
+		goto out;
+
+	kref_init(&gang->kref);
+	mutex_init(&gang->mutex);
+	INIT_LIST_HEAD(&gang->list);
+
+out:
+	return gang;
+}
+
+static void destroy_spu_gang(struct kref *kref)
+{
+	struct spu_gang *gang;
+	gang = container_of(kref, struct spu_gang, kref);
+	WARN_ON(gang->contexts || !list_empty(&gang->list));
+	kfree(gang);
+}
+
+struct spu_gang *get_spu_gang(struct spu_gang *gang)
+{
+	kref_get(&gang->kref);
+	return gang;
+}
+
+int put_spu_gang(struct spu_gang *gang)
+{
+	return kref_put(&gang->kref, &destroy_spu_gang);
+}
+
+void spu_gang_add_ctx(struct spu_gang *gang, struct spu_context *ctx)
+{
+	mutex_lock(&gang->mutex);
+	ctx->gang = get_spu_gang(gang);
+	list_add(&ctx->gang_list, &gang->list);
+	gang->contexts++;
+	mutex_unlock(&gang->mutex);
+}
+
+void spu_gang_remove_ctx(struct spu_gang *gang, struct spu_context *ctx)
+{
+	mutex_lock(&gang->mutex);
+	WARN_ON(ctx->gang != gang);
+	list_del_init(&ctx->gang_list);
+	gang->contexts--;
+	mutex_unlock(&gang->mutex);
+
+	put_spu_gang(gang);
+}