[PATCH 05/14] spufs: Add infrastructure needed for gang scheduling

Arnd Bergmann
2006-10-04T16:35:05Z

[-- Attachment #1: spufs-gang-2.diff --]
[-- Type: text/plain, Size: 15199 bytes --]

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 <arnd.bergmann@de.ibm.com>
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/Makefile
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/Makefile
+++ linux-2.6/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-
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/context.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/context.c
+++ linux-2.6/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(vo
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 *kr
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);
}

Index: linux-2.6/arch/powerpc/platforms/cell/spufs/gang.c
===================================================================
--- /dev/null
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/gang.c
@@ -0,0 +1,81 @@
+/*
+ * SPU file system
+ *
+ * (C) Copyright IBM Deutschland Entwicklung GmbH 2005
+ *
+ * Author: Arnd Bergmann <arndb@de.ibm.com>
+ *
+ * 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);
+}
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/inode.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/inode.c
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/inode.c
@@ -50,6 +50,10 @@ spufs_alloc_inode(struct super_block *sb
ei = kmem_cache_alloc(spufs_inode_cache, SLAB_KERNEL);
if (!ei)
return NULL;
+
+ ei->i_gang = NULL;
+ ei->i_ctx = NULL;
+
return &ei->vfs_inode;
}

@@ -128,14 +132,19 @@ out:
static void
spufs_delete_inode(struct inode *inode)
{
- if (SPUFS_I(inode)->i_ctx)
- put_spu_context(SPUFS_I(inode)->i_ctx);
+ struct spufs_inode_info *ei = SPUFS_I(inode);
+
+ if (ei->i_ctx)
+ put_spu_context(ei->i_ctx);
+ if (ei->i_gang)
+ put_spu_gang(ei->i_gang);
clear_inode(inode);
}

static void spufs_prune_dir(struct dentry *dir)
{
struct dentry *dentry, *tmp;
+
mutex_lock(&dir->d_inode->i_mutex);
list_for_each_entry_safe(dentry, tmp, &dir->d_subdirs, d_u.d_child) {
spin_lock(&dcache_lock);
@@ -156,13 +165,13 @@ static void spufs_prune_dir(struct dentr
mutex_unlock(&dir->d_inode->i_mutex);
}

-/* Caller must hold root->i_mutex */
-static int spufs_rmdir(struct inode *root, struct dentry *dir_dentry)
+/* Caller must hold parent->i_mutex */
+static int spufs_rmdir(struct inode *parent, struct dentry *dir)
{
/* remove all entries */
- spufs_prune_dir(dir_dentry);
+ spufs_prune_dir(dir);

- return simple_rmdir(root, dir_dentry);
+ return simple_rmdir(parent, dir);
}

static int spufs_fill_dir(struct dentry *dir, struct tree_descr *files,
@@ -191,17 +200,17 @@ out:
static int spufs_dir_close(struct inode *inode, struct file *file)
{
struct spu_context *ctx;
- struct inode *dir;
- struct dentry *dentry;
+ struct inode *parent;
+ struct dentry *dir;
int ret;

- dentry = file->f_dentry;
- dir = dentry->d_parent->d_inode;
- ctx = SPUFS_I(dentry->d_inode)->i_ctx;
-
- mutex_lock(&dir->i_mutex);
- ret = spufs_rmdir(dir, dentry);
- mutex_unlock(&dir->i_mutex);
+ dir = file->f_dentry;
+ parent = dir->d_parent->d_inode;
+ ctx = SPUFS_I(dir->d_inode)->i_ctx;
+
+ mutex_lock(&parent->i_mutex);
+ ret = spufs_rmdir(parent, dir);
+ mutex_unlock(&parent->i_mutex);
WARN_ON(ret);

/* We have to give up the mm_struct */
@@ -240,7 +249,7 @@ spufs_mkdir(struct inode *dir, struct de
inode->i_gid = dir->i_gid;
inode->i_mode &= S_ISGID;
}
- ctx = alloc_spu_context();
+ ctx = alloc_spu_context(SPUFS_I(dir)->i_gang); /* XXX gang */
SPUFS_I(inode)->i_ctx = ctx;
if (!ctx)
goto out_iput;
@@ -292,24 +301,177 @@ out:
return ret;
}

+static int spufs_create_context(struct inode *inode,
+ struct dentry *dentry,
+ struct vfsmount *mnt, int flags, int mode)
+{
+ int ret;
+
+ ret = spufs_mkdir(inode, dentry, flags, mode & S_IRWXUGO);
+ if (ret)
+ goto out_unlock;
+
+ /*
+ * get references for dget and mntget, will be released
+ * in error path of *_open().
+ */
+ ret = spufs_context_open(dget(dentry), mntget(mnt));
+ if (ret < 0) {
+ WARN_ON(spufs_rmdir(inode, dentry));
+ mutex_unlock(&inode->i_mutex);
+ spu_forget(SPUFS_I(dentry->d_inode)->i_ctx);
+ goto out;
+ }
+
+out_unlock:
+ mutex_unlock(&inode->i_mutex);
+out:
+ dput(dentry);
+ return ret;
+}
+
+static int spufs_rmgang(struct inode *root, struct dentry *dir)
+{
+ /* FIXME: this fails if the dir is not empty,
+ which causes a leak of gangs. */
+ return simple_rmdir(root, dir);
+}
+
+static int spufs_gang_close(struct inode *inode, struct file *file)
+{
+ struct inode *parent;
+ struct dentry *dir;
+ int ret;
+
+ dir = file->f_dentry;
+ parent = dir->d_parent->d_inode;
+
+ ret = spufs_rmgang(parent, dir);
+ WARN_ON(ret);
+
+ return dcache_dir_close(inode, file);
+}
+
+struct file_operations spufs_gang_fops = {
+ .open = dcache_dir_open,
+ .release = spufs_gang_close,
+ .llseek = dcache_dir_lseek,
+ .read = generic_read_dir,
+ .readdir = dcache_readdir,
+ .fsync = simple_sync_file,
+};
+
+static int
+spufs_mkgang(struct inode *dir, struct dentry *dentry, int mode)
+{
+ int ret;
+ struct inode *inode;
+ struct spu_gang *gang;
+
+ ret = -ENOSPC;
+ inode = spufs_new_inode(dir->i_sb, mode | S_IFDIR);
+ if (!inode)
+ goto out;
+
+ ret = 0;
+ if (dir->i_mode & S_ISGID) {
+ inode->i_gid = dir->i_gid;
+ inode->i_mode &= S_ISGID;
+ }
+ gang = alloc_spu_gang();
+ SPUFS_I(inode)->i_ctx = NULL;
+ SPUFS_I(inode)->i_gang = gang;
+ if (!gang)
+ goto out_iput;
+
+ inode->i_op = &spufs_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+
+ d_instantiate(dentry, inode);
+ dget(dentry);
+ dir->i_nlink++;
+ dentry->d_inode->i_nlink++;
+ return ret;
+
+out_iput:
+ iput(inode);
+out:
+ return ret;
+}
+
+static int spufs_gang_open(struct dentry *dentry, struct vfsmount *mnt)
+{
+ int ret;
+ struct file *filp;
+
+ ret = get_unused_fd();
+ if (ret < 0) {
+ dput(dentry);
+ mntput(mnt);
+ goto out;
+ }
+
+ filp = dentry_open(dentry, mnt, O_RDONLY);
+ if (IS_ERR(filp)) {
+ put_unused_fd(ret);
+ ret = PTR_ERR(filp);
+ goto out;
+ }
+
+ filp->f_op = &spufs_gang_fops;
+ fd_install(ret, filp);
+out:
+ return ret;
+}
+
+static int spufs_create_gang(struct inode *inode,
+ struct dentry *dentry,
+ struct vfsmount *mnt, int mode)
+{
+ int ret;
+
+ ret = spufs_mkgang(inode, dentry, mode & S_IRWXUGO);
+ if (ret)
+ goto out;
+
+ /*
+ * get references for dget and mntget, will be released
+ * in error path of *_open().
+ */
+ ret = spufs_gang_open(dget(dentry), mntget(mnt));
+ if (ret < 0)
+ WARN_ON(spufs_rmgang(inode, dentry));
+
+out:
+ mutex_unlock(&inode->i_mutex);
+ dput(dentry);
+ return ret;
+}
+
+
static struct file_system_type spufs_type;

-long spufs_create_thread(struct nameidata *nd,
- unsigned int flags, mode_t mode)
+long spufs_create(struct nameidata *nd, unsigned int flags, mode_t mode)
{
struct dentry *dentry;
int ret;

- /* need to be at the root of spufs */
ret = -EINVAL;
- if (nd->dentry->d_sb->s_type != &spufs_type ||
- nd->dentry != nd->dentry->d_sb->s_root)
+ /* check if we are on spufs */
+ if (nd->dentry->d_sb->s_type != &spufs_type)
goto out;

- /* all flags are reserved */
+ /* don't accept undefined flags */
if (flags & (~SPU_CREATE_FLAG_ALL))
goto out;

+ /* only threads can be underneath a gang */
+ if (nd->dentry != nd->dentry->d_sb->s_root) {
+ if ((flags & SPU_CREATE_GANG) ||
+ !SPUFS_I(nd->dentry->d_inode)->i_gang)
+ goto out;
+ }
+
dentry = lookup_create(nd, 1);
ret = PTR_ERR(dentry);
if (IS_ERR(dentry))
@@ -320,22 +482,13 @@ long spufs_create_thread(struct nameidat
goto out_dput;

mode &= ~current->fs->umask;
- ret = spufs_mkdir(nd->dentry->d_inode, dentry, flags, mode & S_IRWXUGO);
- if (ret)
- goto out_dput;

- /*
- * get references for dget and mntget, will be released
- * in error path of *_open().
- */
- ret = spufs_context_open(dget(dentry), mntget(nd->mnt));
- if (ret < 0) {
- WARN_ON(spufs_rmdir(nd->dentry->d_inode, dentry));
- mutex_unlock(&nd->dentry->d_inode->i_mutex);
- spu_forget(SPUFS_I(dentry->d_inode)->i_ctx);
- dput(dentry);
- goto out;
- }
+ if (flags & SPU_CREATE_GANG)
+ return spufs_create_gang(nd->dentry->d_inode,
+ dentry, nd->mnt, mode);
+ else
+ return spufs_create_context(nd->dentry->d_inode,
+ dentry, nd->mnt, flags, mode);

out_dput:
dput(dentry);
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/spufs.h
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/spufs.h
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -39,6 +39,8 @@ struct spu_context_ops;

#define SPU_CONTEXT_PREEMPT 0UL

+struct spu_gang;
+
struct spu_context {
struct spu *spu; /* pointer to a physical SPU */
struct spu_state csa; /* SPU context save area. */
@@ -68,6 +70,16 @@ struct spu_context {
struct work_struct reap_work;
unsigned long flags;
unsigned long event_return;
+
+ struct list_head gang_list;
+ struct spu_gang *gang;
+};
+
+struct spu_gang {
+ struct list_head list;
+ struct mutex mutex;
+ struct kref kref;
+ int contexts;
};

struct mfc_dma_command {
@@ -115,6 +127,7 @@ extern struct spu_context_ops spu_backin

struct spufs_inode_info {
struct spu_context *i_ctx;
+ struct spu_gang *i_gang;
struct inode vfs_inode;
};
#define SPUFS_I(inode) \
@@ -125,12 +138,19 @@ extern struct tree_descr spufs_dir_conte
/* system call implementation */
long spufs_run_spu(struct file *file,
struct spu_context *ctx, u32 *npc, u32 *status);
-long spufs_create_thread(struct nameidata *nd,
+long spufs_create(struct nameidata *nd,
unsigned int flags, mode_t mode);
extern struct file_operations spufs_context_fops;

+/* gang management */
+struct spu_gang *alloc_spu_gang(void);
+struct spu_gang *get_spu_gang(struct spu_gang *gang);
+int put_spu_gang(struct spu_gang *gang);
+void spu_gang_remove_ctx(struct spu_gang *gang, struct spu_context *ctx);
+void spu_gang_add_ctx(struct spu_gang *gang, struct spu_context *ctx);
+
/* context management */
-struct spu_context * alloc_spu_context(void);
+struct spu_context * alloc_spu_context(struct spu_gang *gang);
void destroy_spu_context(struct kref *kref);
struct spu_context * get_spu_context(struct spu_context *ctx);
int put_spu_context(struct spu_context *ctx);
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/syscalls.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/syscalls.c
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/syscalls.c
@@ -90,7 +90,7 @@ asmlinkage long sys_spu_create(const cha
ret = path_lookup(tmp, LOOKUP_PARENT|
LOOKUP_OPEN|LOOKUP_CREATE, &nd);
if (!ret) {
- ret = spufs_create_thread(&nd, flags, mode);
+ ret = spufs_create(&nd, flags, mode);
path_release(&nd);
}
putname(tmp);
Index: linux-2.6/include/asm-powerpc/spu.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/spu.h
+++ linux-2.6/include/asm-powerpc/spu.h
@@ -181,7 +181,10 @@ extern struct spufs_calls {
* Flags for sys_spu_create.
*/
#define SPU_CREATE_EVENTS_ENABLED 0x0001
-#define SPU_CREATE_FLAG_ALL 0x0001 /* mask of all valid flags */
+#define SPU_CREATE_GANG 0x0002
+
+#define SPU_CREATE_FLAG_ALL 0x0003 /* mask of all valid flags */
+

#ifdef CONFIG_SPU_FS_MODULE
int register_spu_syscalls(struct spufs_calls *calls);

--