[POWERPC] spufs: Add tid file

The new tid file contains the ID of the thread currently running the
context, if any.  This is used so that the new spu-top and spu-ps
tools can find the thread in /proc.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

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

@@ -2039,6 +2039,26 @@ static const struct file_operations spufs_proxydma_info_fops = {
 	.read = spufs_proxydma_info_read,
 };
 
+static int spufs_show_tid(struct seq_file *s, void *private)
+{
+	struct spu_context *ctx = s->private;
+
+	seq_printf(s, "%d\n", ctx->tid);
+	return 0;
+}
+
+static int spufs_tid_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, spufs_show_tid, SPUFS_I(inode)->i_ctx);
+}
+
+static const struct file_operations spufs_tid_fops = {
+	.open		= spufs_tid_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 struct tree_descr spufs_dir_contents[] = {
 	{ "capabilities", &spufs_caps_fops, 0444, },
 	{ "mem",  &spufs_mem_fops,  0666, },
@@ -2072,6 +2092,7 @@ struct tree_descr spufs_dir_contents[] = {
 	{ "wbox_info", &spufs_wbox_info_fops, 0444, },
 	{ "dma_info", &spufs_dma_info_fops, 0444, },
 	{ "proxydma_info", &spufs_proxydma_info_fops, 0444, },
+	{ "tid", &spufs_tid_fops, 0444, },
 	{},
 };
 
@@ -2095,6 +2116,7 @@ struct tree_descr spufs_dir_nosched_contents[] = {
 	{ "psmap", &spufs_psmap_fops, 0666, },
 	{ "phys-id", &spufs_id_ops, 0666, },
 	{ "object-id", &spufs_object_id_ops, 0666, },
+	{ "tid", &spufs_tid_fops, 0444, },
 	{},
 };
 

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

@@ -101,6 +101,13 @@ void spu_set_timeslice(struct spu_context *ctx)
  */
 void __spu_update_sched_info(struct spu_context *ctx)
 {
+	/*
+	 * 32-Bit assignment are atomic on powerpc, and we don't care about
+	 * memory ordering here because retriving the controlling thread is
+	 * per defintion racy.
+	 */
+	ctx->tid = current->pid;
+
 	/*
 	 * We do our own priority calculations, so we normally want
 	 * ->static_prio to start with. Unfortunately thies field

arch/powerpc/platforms/cell/spufs/spufs.h

@@ -77,6 +77,9 @@ struct spu_context {
 	struct list_head gang_list;
 	struct spu_gang *gang;
 
+	/* owner thread */
+	pid_t tid;
+
 	/* scheduler fields */
 	struct list_head rq;
 	unsigned int time_slice;