Re: [Cbe-oss-dev] [PATCH] Cell SPU task notification

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Christoph Hellwig wrote:

Index: linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/sched.c
===================================================================
--- linux-2.6.19-rc6-arnd1+patches.orig/arch/powerpc/platforms/cell/spufs/sched.c	2006-12-04 10:56:04.730698720 -0600
+++ linux-2.6.19-rc6-arnd1+patches/arch/powerpc/platforms/cell/spufs/sched.c	2007-01-15 16:22:31.808461448 -0600
@@ -84,15 +84,42 @@
			    ctx ? ctx->object_id : 0, spu);
}

+static void notify_spus_active(void)
+{
+       int node;
+	/* Wake up the active spu_contexts. When the awakened processes
+	 * sees their notify_active flag is set, they will call
+	 * spu_notify_already_active().
+	 */
+	for (node = 0; node < MAX_NUMNODES; node++) {
+		struct spu *spu;
+		mutex_lock(&spu_prio->active_mutex[node]);
+                list_for_each_entry(spu, &spu_prio->active_list[node], list) {

	You seem to have some issues with tabs vs spaces for indentation
	here.
fixed

+			struct spu_context *ctx = spu->ctx;
+			spu->notify_active = 1;


	Please make this a bit in the sched_flags field that's added in
	the scheduler patch series I sent out.
I haven't seen that the scheduler patch series got applied yet. This Cell spu task notification patch is a pre-req for OProfile development to support profiling SPUs. When the scheduler patch gets applied to a kernel version that fits our needs for our OProfile development, I don't see any problem in using the sched_flags field instead of notify_active.

+			wake_up_all(&ctx->stop_wq);
+			smp_wmb();
+		}
+                mutex_unlock(&spu_prio->active_mutex[node]);
+	}
+	yield();
+}

	Why do you add the yield() here?  yield is pretty much a sign
	for a bug
Yes, the yield() and the memory barriers were leftovers from an earlier ill-conceived attempt at solving this problem. They should have been removed. They're gone now.

+void spu_notify_already_active(struct spu_context *ctx)
+{
+	struct spu *spu = ctx->spu;
+	if (!spu)
+		return;
+	spu_switch_notify(spu, ctx);
+}

	Please just call spu_switch_notify directly from the only
I hesitated doing this since it would entail changing spu_switch_notify from being static to non-static. I'd like to get Arnd's opinion on this question before going ahead and making such a change.

	caller.  Also the check for ctx->spu beeing there is not
	required if you look a the caller.


	*stat = ctx->ops->status_read(ctx);
-	if (ctx->state != SPU_STATE_RUNNABLE)
-		return 1;
+	smp_rmb();

	What do you need the barrier for here?
Removed.


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