powerpc/spufs: Improve search of node for contexts with SPU affinity

This patch improves redability of the code responsible for trying to find
a node with enough SPUs not committed to other affinity gangs.

An additional check is also added, to avoid taking into account gangs that
have no SPU affinity.

Signed-off-by: Andre Detsch <adetsch@br.ibm.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

1 files changed, 13 insertions, 6 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 67595bc380dc..6253df5a436e 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -312,6 +312,15 @@ static struct spu *aff_ref_location(struct spu_context *ctx, int mem_aff,
          */
         node = cpu_to_node(raw_smp_processor_id());
         for (n = 0; n < MAX_NUMNODES; n++, node++) {
+                /*
+                 * "available_spus" counts how many spus are not potentially
+                 * going to be used by other affinity gangs whose reference
+                 * context is already in place. Although this code seeks to
+                 * avoid having affinity gangs with a summed amount of
+                 * contexts bigger than the amount of spus in the node,
+                 * this may happen sporadically. In this case, available_spus
+                 * becomes negative, which is harmless.
+                 */
                 int available_spus;
 
                 node = (node < MAX_NUMNODES) ? node : 0;
@@ -321,12 +330,10 @@ static struct spu *aff_ref_location(struct spu_context *ctx, int mem_aff,
                 available_spus = 0;
                 mutex_lock(&cbe_spu_info[node].list_mutex);
                 list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
-                        if (spu->ctx && spu->ctx->gang
-                                        && spu->ctx->aff_offset == 0)
-                                available_spus -=
-                                        (spu->ctx->gang->contexts - 1);
-                        else
-                                available_spus++;
+                        if (spu->ctx && spu->ctx->gang && !spu->ctx->aff_offset
+                                        && spu->ctx->gang->aff_ref_spu)
+                                available_spus -= spu->ctx->gang->contexts;
+                        available_spus++;
                 }
                 if (available_spus < ctx->gang->contexts) {
                         mutex_unlock(&cbe_spu_info[node].list_mutex);