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