diff --git a/arch/powerpc/include/asm/spu.h b/arch/powerpc/include/asm/spu.h
index 8b2eb04..071dbb8 100644
--- a/arch/powerpc/include/asm/spu.h
+++ b/arch/powerpc/include/asm/spu.h
@@ -137,6 +137,7 @@ struct spu {
 	unsigned int slb_replace;
 	struct mm_struct *mm;
 	struct spu_context *ctx;
+	struct spu_gang *gang;
 	struct spu_runqueue *rq;
 	unsigned long long timestamp;
 	pid_t pid;
diff --git a/arch/powerpc/platforms/cell/spufs/context.c b/arch/powerpc/platforms/cell/spufs/context.c
index 85b5c1f..b810050 100644
--- a/arch/powerpc/platforms/cell/spufs/context.c
+++ b/arch/powerpc/platforms/cell/spufs/context.c
@@ -68,9 +68,9 @@ struct spu_context *alloc_spu_context(struct spu_gang *gang)
 	init_waitqueue_head(&ctx->mfc_wq);
 	init_waitqueue_head(&ctx->run_wq);
 	ctx->state = SPU_STATE_SAVED;
+	set_bit(SPU_SCHED_JUST_CREATED, &ctx->sched_flags);
 	ctx->ops = &spu_backing_ops;
 	ctx->owner = get_task_mm(current);
-	INIT_LIST_HEAD(&ctx->rq);
 	INIT_LIST_HEAD(&ctx->aff_list);
 	spu_gang_add_ctx(gang, ctx);
 	spu_update_sched_info(ctx);
@@ -98,14 +98,19 @@ void destroy_spu_context(struct kref *kref)
 	gang = ctx->gang;
 
 	spu_context_nospu_trace(destroy_spu_context__enter, ctx);
-	mutex_lock(&ctx->state_mutex);
-	spu_deactivate(ctx);
-	mutex_unlock(&ctx->state_mutex);
+
+	/*
+	 * Deactivate and make it non-runnable while we work on it.
+	 */
+	mutex_lock(&gang->mutex);
+	WARN_ON(ctx->gang != gang);
+	spu_deactivate(gang);
+	mutex_unlock(&gang->mutex);
+
 	spu_fini_csa(&ctx->csa);
 	spu_gang_remove_ctx(ctx->gang, ctx);
 	if (ctx->prof_priv_kref)
 		kref_put(ctx->prof_priv_kref, ctx->prof_priv_release);
-	BUG_ON(!list_empty(&ctx->rq));
 	atomic_dec(&nr_spu_contexts);
 	kfree(ctx->switch_log);
 	kfree(ctx);
@@ -126,20 +131,19 @@ int put_spu_context(struct spu_context *ctx)
 void spu_forget(struct spu_context *ctx)
 {
 	struct mm_struct *mm;
+	struct spu_gang *gang = ctx->gang;
 
 	/*
-	 * This is basically an open-coded spu_acquire_saved, except that
-	 * we don't acquire the state mutex interruptible, and we don't
-	 * want this context to be rescheduled on release.
+	 * The context is being destroyed but the gang may live on as there
+	 * is no requirement that all contexts within the gang have to die
+	 * at the same time.
 	 */
-	mutex_lock(&ctx->state_mutex);
-	if (ctx->state != SPU_STATE_SAVED)
-		spu_deactivate(ctx);
-
+	mutex_lock(&gang->mutex);
+	spu_deactivate(gang);
 	mm = ctx->owner;
 	ctx->owner = NULL;
 	mmput(mm);
-	spu_release(ctx);
+	mutex_unlock(&gang->mutex);
 }
 
 void spu_unmap_mappings(struct spu_context *ctx)
@@ -168,18 +172,21 @@ void spu_unmap_mappings(struct spu_context *ctx)
  */
 int spu_acquire_saved(struct spu_context *ctx)
 {
+	struct spu_gang *gang = ctx->gang;
 	int ret;
 
 	spu_context_nospu_trace(spu_acquire_saved__enter, ctx);
 
-	ret = spu_acquire(ctx);
+	ret = mutex_lock_interruptible(&gang->mutex);
 	if (ret)
 		return ret;
 
-	if (ctx->state != SPU_STATE_SAVED) {
-		set_bit(SPU_SCHED_WAS_ACTIVE, &ctx->sched_flags);
-		spu_deactivate(ctx);
-	}
+	/*
+	 * Deactivate unconditionally as we leave holding the gang lock.
+	 * If the gang is on the runqueue, the scheduler would block on it,
+	 * if it tried to dispatch it.
+	 */
+	spu_deactivate(gang);
 
 	return 0;
 }
@@ -190,10 +197,12 @@ int spu_acquire_saved(struct spu_context *ctx)
  */
 void spu_release_saved(struct spu_context *ctx)
 {
+	mutex_lock(&ctx->state_mutex);
+	mutex_unlock(&ctx->gang->mutex);
+
 	BUG_ON(ctx->state != SPU_STATE_SAVED);
 
-	if (test_and_clear_bit(SPU_SCHED_WAS_ACTIVE, &ctx->sched_flags) &&
-			test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
+	if (test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
 		spu_activate(ctx, 0);
 
 	spu_release(ctx);
diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index 1b26071..a02ee25 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -2649,7 +2649,7 @@ static int spufs_show_ctx(struct seq_file *s, void *private)
 		ctx->prio,
 		ctx->time_slice,
 		ctx->spu ? ctx->spu->number : -1,
-		!list_empty(&ctx->rq) ? 'q' : ' ',
+		!list_empty(&ctx->gang->rq) ? 'q' : ' ',
 		ctx->csa.class_0_pending,
 		ctx->csa.class_0_dar,
 		ctx->csa.class_1_dsisr,
diff --git a/arch/powerpc/platforms/cell/spufs/gang.c b/arch/powerpc/platforms/cell/spufs/gang.c
index 2a01271..3fcbdc7 100644
--- a/arch/powerpc/platforms/cell/spufs/gang.c
+++ b/arch/powerpc/platforms/cell/spufs/gang.c
@@ -38,6 +38,7 @@ struct spu_gang *alloc_spu_gang(void)
 	mutex_init(&gang->aff_mutex);
 	INIT_LIST_HEAD(&gang->list);
 	INIT_LIST_HEAD(&gang->aff_list_head);
+	INIT_LIST_HEAD(&gang->rq);
 
 	/*
 	 * Inherit scheduling parameters from the creator of the gang.
@@ -91,7 +92,16 @@ void spu_gang_remove_ctx(struct spu_gang *gang, struct spu_context *ctx)
 	}
 	list_del_init(&ctx->gang_list);
 	gang->contexts--;
-	mutex_unlock(&gang->mutex);
+	atomic_dec(&gang->nstarted);
+	if (spu_gang_runnable(gang)) {
+		ctx = list_first_entry(&gang->list,
+				struct spu_context, gang_list);
+		mutex_lock(&ctx->state_mutex);
+		mutex_unlock(&gang->mutex);
+		spu_activate(ctx, 0);
+		mutex_unlock(&ctx->state_mutex);
+	} else
+		mutex_unlock(&gang->mutex);
 
 	put_spu_gang(gang);
 }
diff --git a/arch/powerpc/platforms/cell/spufs/run.c b/arch/powerpc/platforms/cell/spufs/run.c
index c58bd36..cbce273 100644
--- a/arch/powerpc/platforms/cell/spufs/run.c
+++ b/arch/powerpc/platforms/cell/spufs/run.c
@@ -172,11 +172,45 @@ out:
 static int spu_run_init(struct spu_context *ctx, u32 *npc)
 {
 	unsigned long runcntl = SPU_RUNCNTL_RUNNABLE;
+	struct spu_gang *gang = ctx->gang;
 	int ret;
 
 	spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
 
 	/*
+	 * Gang start.  The nstarted variable is incremented the first
+	 * time that a context is started.  When all ctxts in a gang have
+	 * been started, the gang is considered runnable.
+	 *
+	 * Gang runnable.  The nrunnable variable is the number of
+	 * contexts that are currently being processed by spufs_run_spu.
+	 * The count is incremented on entry and decremented on return
+	 * to user mode.  When a context is in user mode, the spu is
+	 * stopped.  When the count goes to zero, the gang is unloaded
+	 * if there is another gang waiting to run.  In this case, it
+	 * is unloaded, but it is not added to the runqueue as there
+	 * are no runnable contexts in the gang.  There has to be at
+	 * least one runnable context to be added to the runq.  In this
+	 * way, we prevent the runqueue from being over run with non-
+	 * runnable contexts.  The gang is guaranteed to be put back on
+	 * the runqueue, when a context is started again.  This is
+	 * driven explcitly by the program.
+	 *
+	 * Gang preemption. In addition to the case mentioned above
+	 * when all of the contexts are invoking user mode code, the
+	 * gang is also preempted when all of the contexts are either
+	 * in user mode or processing page faults.  The nfaulting variable
+	 * is the number of contexts in a gang that are currently
+	 * processing page faults.  When it equals nrunnable, the gang
+	 * is yielded and another gang runs if there is one on the
+	 * runqueue.  In this case, the gang is added to the runqueue
+	 * as the nrunnable field is still positive.
+	 */
+	if (test_and_clear_bit(SPU_SCHED_JUST_CREATED, &ctx->sched_flags))
+		atomic_inc(&gang->nstarted);
+	atomic_inc(&gang->nrunnable);
+
+	/*
 	 * NOSCHED is synchronous scheduling with respect to the caller.
 	 * The caller waits for the context to be loaded.
 	 */
@@ -242,8 +276,6 @@ static int spu_run_fini(struct spu_context *ctx, u32 *npc,
 {
 	int ret = 0;
 
-	spu_del_from_rq(ctx);
-
 	*status = ctx->ops->status_read(ctx);
 	*npc = ctx->ops->npc_read(ctx);
 
@@ -252,6 +284,8 @@ static int spu_run_fini(struct spu_context *ctx, u32 *npc,
 	spu_switch_log_notify(NULL, ctx, SWITCH_LOG_EXIT, *status);
 	spu_release(ctx);
 
+	atomic_dec(&ctx->gang->nrunnable);
+
 	if (signal_pending(current))
 		ret = -ERESTARTSYS;
 
@@ -357,6 +391,18 @@ long spufs_run_spu(struct spu_context *ctx, u32 *npc, u32 *event)
 
 	ctx->event_return = 0;
 
+	/*
+	 * This routine is almost entirely context based and runs mostly
+	 * under the context lock.  The locking strategy is driven by the
+	 * state of the context.  On input, the gang and context locks are
+	 * taken if the context is in the non-runnable state.  Both locks
+	 * are required to activate the context as it is a gang level
+	 * operation.  This occurs before the loop in spu_run_init. The
+	 * loop itself is processed just with the context lock and if the
+	 * system call returns and is re-entered as long as the context
+	 * remains in the runnable state, the gang lock is not required
+	 * as the context does not need to be activated.
+	 */
 	ret = spu_acquire(ctx);
 	if (ret)
 		goto out_unlock;
diff --git a/arch/powerpc/platforms/cell/spufs/sched.c b/arch/powerpc/platforms/cell/spufs/sched.c
index 1fc0c3d..3c83bd3 100644
--- a/arch/powerpc/platforms/cell/spufs/sched.c
+++ b/arch/powerpc/platforms/cell/spufs/sched.c
@@ -48,11 +48,39 @@
 #include <asm/spu_priv1.h>
 #include "spufs.h"
 
+/*
+ * Gang scheduling locking strategy.
+ *
+ * All contexts in a gang are scheduled / unscheduled at the same time.
+ * Several locks have to be taken at the same time to make this happen
+ * atomically.  The hierarchy is gang, ctxt, runq_lock, and
+ * cbe_spu_info[].list_mutex.  The gang lock is taken principally to ensure
+ * that additional contexts cannot be added or removed while the scheduler
+ * is operating on the gang.  The ctxt lock must be taken to serialize
+ * access to physical spu resources including registers, state save,
+ * and restore.  The runqueue lock to synchronize access to the runqueue
+ * and to ensure that the view of available resources and active gangs
+ * is perfomed atomically across the system.  The list_mutex is needed
+ * to allocate and free individual spu resources.
+ */
+
+struct spu_sched_stats {
+	int inode;	/* node with the most idle spus (idle node) */
+	int inode_icnt;	/* count of idle spus on idle node */
+	int inode_pcnt;	/* count of preemptible spus on idle node */
+	int pnode;	/* node with the most preemptible spus (preempt node) */
+	int pnode_icnt;	/* count of idle spus on preempt node */
+	int pnode_pcnt; /* count of preemptible spus on preempt node */
+	int total_icnt; /* total idle spus across system */
+	int total_pcnt; /* total preemptible spus across system */
+};
+
 struct spu_prio_array {
 	DECLARE_BITMAP(bitmap, MAX_PRIO);
 	struct list_head runq[MAX_PRIO];
 	struct mutex runq_lock;
 	int nr_waiting;
+	int nr_contexts;
 };
 
 static unsigned long spu_avenrun[3];
@@ -60,6 +88,7 @@ static struct spu_prio_array *spu_prio;
 static struct task_struct *spusched_task;
 static struct timer_list spusched_timer;
 static struct timer_list spuloadavg_timer;
+static void spu_unschedule(struct spu_gang *gang);
 
 /*
  * Priority of a normal, non-rt, non-niced'd process (aka nice level 0).
@@ -85,6 +114,14 @@ static struct timer_list spuloadavg_timer;
 #define SCALE_PRIO(x, prio) \
 	max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_SPU_TIMESLICE)
 
+/* These constants are used when reserving spus for gang scheduling. */
+#define SPU_RESERVE		0
+#define SPU_RESERVE_UNDO	1
+
+/* Constants used by the scheduler's placement algorithm. */
+#define SPU_PLACE_NONE		-2
+#define SPU_PLACE_ALL		-1
+
 /*
  * scale user-nice values [ -20 ... 0 ... 19 ] to time slice values:
  * [800ms ... 100ms ... 5ms]
@@ -109,12 +146,6 @@ void spu_set_timeslice(struct spu_context *ctx)
 static void __spu_update_sched_info(struct spu_context *ctx)
 {
 	/*
-	 * assert that the context is not on the runqueue, so it is safe
-	 * to change its scheduling parameters.
-	 */
-	BUG_ON(!list_empty(&ctx->rq));
-
-	/*
 	 * 32-Bit assignments are atomic on powerpc, and we don't care about
 	 * memory ordering here because retrieving the controlling thread is
 	 * per definition racy.
@@ -178,25 +209,25 @@ void spu_update_sched_info(struct spu_context *ctx)
 	}
 }
 
-static int __node_allowed(struct spu_context *ctx, int node)
+static int __node_allowed(struct spu_gang *gang, int node)
 {
 	if (nr_cpus_node(node)) {
 		cpumask_t mask = node_to_cpumask(node);
 
-		if (cpus_intersects(mask, ctx->cpus_allowed))
+		if (cpus_intersects(mask, gang->cpus_allowed))
 			return 1;
 	}
 
 	return 0;
 }
 
-static int node_allowed(struct spu_context *ctx, int node)
+static int node_allowed(struct spu_gang *gang, int node)
 {
 	int rval;
 
-	mutex_lock(&spu_prio->runq_lock);
-	rval = __node_allowed(ctx, node);
-	mutex_unlock(&spu_prio->runq_lock);
+	mutex_lock(&cbe_spu_info[node].list_mutex);
+	rval = __node_allowed(gang, node);
+	mutex_unlock(&cbe_spu_info[node].list_mutex);
 
 	return rval;
 }
@@ -339,7 +370,7 @@ static struct spu *aff_ref_location(struct spu_context *ctx, int mem_aff,
 		int available_spus;
 
 		node = (node < MAX_NUMNODES) ? node : 0;
-		if (!node_allowed(ctx, node))
+		if (!node_allowed(ctx->gang, node))
 			continue;
 
 		available_spus = 0;
@@ -421,15 +452,17 @@ static struct spu *ctx_location(struct spu *ref, int offset, int node)
  * affinity_check is called each time a context is going to be scheduled.
  * It returns the spu ptr on which the context must run.
  */
-static int has_affinity(struct spu_context *ctx)
+static int has_affinity(struct spu_gang *gang)
 {
-	struct spu_gang *gang = ctx->gang;
-
-	if (list_empty(&ctx->aff_list))
+	if (list_empty(&gang->aff_list_head))
 		return 0;
 
-	if (atomic_read(&ctx->gang->aff_sched_count) == 0)
-		ctx->gang->aff_ref_spu = NULL;
+	/*
+	 * TODO: fix SPU Affinity to work with gang scheduling.
+	 */
+
+	if (atomic_read(&gang->aff_sched_count) == 0)
+		gang->aff_ref_spu = NULL;
 
 	if (!gang->aff_ref_spu) {
 		if (!(gang->aff_flags & AFF_MERGED))
@@ -501,297 +534,463 @@ static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
 }
 
 /**
- * spu_add_to_rq - add a context to the runqueue
- * @ctx:       context to add
+ * spu_add_to_rq - add a gang to the runqueue
+ * @gang:       gang to add
  */
-static void __spu_add_to_rq(struct spu_context *ctx)
+static void __spu_add_to_rq(struct spu_gang *gang)
 {
-	/*
-	 * Unfortunately this code path can be called from multiple threads
-	 * on behalf of a single context due to the way the problem state
-	 * mmap support works.
-	 *
-	 * Fortunately we need to wake up all these threads at the same time
-	 * and can simply skip the runqueue addition for every but the first
-	 * thread getting into this codepath.
-	 *
-	 * It's still quite hacky, and long-term we should proxy all other
-	 * threads through the owner thread so that spu_run is in control
-	 * of all the scheduling activity for a given context.
-	 */
-	if (list_empty(&ctx->rq)) {
-		list_add_tail(&ctx->rq, &spu_prio->runq[ctx->prio]);
-		set_bit(ctx->prio, spu_prio->bitmap);
+	if (atomic_read(&gang->nrunnable) && list_empty(&gang->rq)) {
+		int prio = gang->prio;
+
+		list_add_tail(&gang->rq, &spu_prio->runq[prio]);
+		set_bit(prio, spu_prio->bitmap);
+		spu_prio->nr_contexts += gang->contexts;
 		if (!spu_prio->nr_waiting++)
 			__mod_timer(&spusched_timer, jiffies + SPUSCHED_TICK);
 	}
 }
 
-static void spu_add_to_rq(struct spu_context *ctx)
+static void spu_add_to_rq(struct spu_gang *gang)
 {
 	mutex_lock(&spu_prio->runq_lock);
-	__spu_add_to_rq(ctx);
+	__spu_add_to_rq(gang);
 	mutex_unlock(&spu_prio->runq_lock);
 }
 
-static void __spu_del_from_rq(struct spu_context *ctx)
+static void __spu_del_from_rq(struct spu_gang *gang)
 {
-	int prio = ctx->prio;
+	if (!list_empty(&gang->rq)) {
+		int prio = gang->prio;
 
-	if (!list_empty(&ctx->rq)) {
+		spu_prio->nr_contexts -= gang->contexts;
 		if (!--spu_prio->nr_waiting)
 			del_timer(&spusched_timer);
-		list_del_init(&ctx->rq);
-
+		list_del_init(&gang->rq);
 		if (list_empty(&spu_prio->runq[prio]))
 			clear_bit(prio, spu_prio->bitmap);
 	}
 }
 
-void spu_del_from_rq(struct spu_context *ctx)
+static void spu_del_from_rq(struct spu_gang *gang)
 {
 	mutex_lock(&spu_prio->runq_lock);
-	__spu_del_from_rq(ctx);
+	__spu_del_from_rq(gang);
 	mutex_unlock(&spu_prio->runq_lock);
 }
 
-static void spu_prio_wait(struct spu_context *ctx)
-{
-	DEFINE_WAIT(wait);
-
-	/*
-	 * The caller must explicitly wait for a context to be loaded
-	 * if the nosched flag is set.  If NOSCHED is not set, the caller
-	 * queues the context and waits for an spu event or error.
-	 */
-	BUG_ON(!(ctx->flags & SPU_CREATE_NOSCHED));
 
-	mutex_lock(&spu_prio->runq_lock);
-	prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
-	if (!signal_pending(current)) {
-		__spu_add_to_rq(ctx);
-		mutex_unlock(&spu_prio->runq_lock);
-		mutex_unlock(&ctx->state_mutex);
-		schedule();
-		mutex_lock(&ctx->state_mutex);
-		mutex_lock(&spu_prio->runq_lock);
-		__spu_del_from_rq(ctx);
-	}
-	mutex_unlock(&spu_prio->runq_lock);
-	__set_current_state(TASK_RUNNING);
-	remove_wait_queue(&ctx->stop_wq, &wait);
-}
-
-static struct spu *spu_get_idle(struct spu_context *ctx)
+static struct spu *spu_bind(struct spu_gang *gang,
+				struct spu_context *ctx, int node)
 {
-	struct spu *spu, *aff_ref_spu;
-	int node, n;
-
-	spu_context_nospu_trace(spu_get_idle__enter, ctx);
-
-	if (ctx->gang) {
-		mutex_lock(&ctx->gang->aff_mutex);
-		if (has_affinity(ctx)) {
-			aff_ref_spu = ctx->gang->aff_ref_spu;
-			atomic_inc(&ctx->gang->aff_sched_count);
-			mutex_unlock(&ctx->gang->aff_mutex);
-			node = aff_ref_spu->node;
+	struct spu *spu;
+	int n;
 
-			mutex_lock(&cbe_spu_info[node].list_mutex);
-			spu = ctx_location(aff_ref_spu, ctx->aff_offset, node);
-			if (spu && spu->alloc_state == SPU_FREE)
-				goto found;
-			mutex_unlock(&cbe_spu_info[node].list_mutex);
+	if (node == SPU_PLACE_ALL)
+		node = cpu_to_node(raw_smp_processor_id());
 
-			atomic_dec(&ctx->gang->aff_sched_count);
-			goto not_found;
-		}
-		mutex_unlock(&ctx->gang->aff_mutex);
-	}
-	node = cpu_to_node(raw_smp_processor_id());
 	for (n = 0; n < MAX_NUMNODES; n++, node++) {
 		node = (node < MAX_NUMNODES) ? node : 0;
-		if (!node_allowed(ctx, node))
+		if (!node_allowed(gang, node))
 			continue;
 
 		mutex_lock(&cbe_spu_info[node].list_mutex);
 		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
-			if (spu->alloc_state == SPU_FREE)
+			if ((spu->alloc_state == SPU_FREE) &&
+			    (spu->gang == gang))
 				goto found;
 		}
 		mutex_unlock(&cbe_spu_info[node].list_mutex);
 	}
-
- not_found:
-	spu_context_nospu_trace(spu_get_idle__not_found, ctx);
 	return NULL;
 
- found:
+found:
+	cbe_spu_info[node].nr_active++;
 	spu->alloc_state = SPU_USED;
+	spu->ctx = ctx;
 	mutex_unlock(&cbe_spu_info[node].list_mutex);
-	spu_context_trace(spu_get_idle__found, ctx, spu);
-	spu_init_channels(spu);
+
 	return spu;
 }
 
+static void __spu_schedule(struct spu_gang *gang, int node_chosen)
+{
+	struct spu_context *ctx;
+	struct spu *spu;
+
+	spu_del_from_rq(gang);
+
+	list_for_each_entry(ctx, &gang->list, gang_list) {
+		mutex_lock(&ctx->state_mutex);
+		BUG_ON(ctx->spu);
+		spu = spu_bind(gang, ctx, node_chosen);
+		BUG_ON(!spu);
+		spu_bind_context(spu, ctx);
+		spu_set_timeslice(ctx);
+		wake_up_all(&ctx->run_wq);
+		mutex_unlock(&ctx->state_mutex);
+	}
+}
+
+static void spu_unschedule(struct spu_gang *gang)
+{
+	struct spu_context *ctx;
+	struct spu *spu;
+	int node;
+
+	list_for_each_entry(ctx, &gang->list, gang_list) {
+
+		mutex_lock(&ctx->state_mutex);
+		spu = ctx->spu;
+		BUG_ON(!spu);
+		BUG_ON(spu->ctx != ctx);
+		BUG_ON(spu->gang != gang);
+		BUG_ON(spu->alloc_state != SPU_USED);
+		node = spu->node;
+		spu_unbind_context(spu, ctx);
+		mutex_lock(&cbe_spu_info[node].list_mutex);
+		cbe_spu_info[node].nr_active--;
+		spu->alloc_state = SPU_FREE;
+		spu->ctx = NULL;
+		spu->gang = NULL;
+		ctx->stats.invol_ctx_switch++;
+		spu->stats.invol_ctx_switch++;
+		mutex_unlock(&cbe_spu_info[node].list_mutex);
+		mutex_unlock(&ctx->state_mutex);
+	}
+}
+
+static int spu_get_idle(struct spu_gang *gang, int node)
+{
+	struct spu *spu;
+	int n, lnode, count, mode;
+	int ret = 0, found = 0;
+
+	spu_context_nospu_trace(spu_get_idle__enter, gang);
+
+	/* TO DO: SPU affinity scheduling. */
+
+	mode = SPU_RESERVE;
+
+spu_get_idle_top:
+
+	if (node == SPU_PLACE_ALL)
+		lnode = cpu_to_node(raw_smp_processor_id());
+	else
+		lnode = node;
+
+	for (n = 0, count = 0;
+	     n < MAX_NUMNODES && count < gang->contexts;
+	     n++, lnode++) {
+
+		lnode = (lnode < MAX_NUMNODES) ? lnode : 0;
+		if (!node_allowed(gang, lnode))
+			continue;
+
+		mutex_lock(&cbe_spu_info[lnode].list_mutex);
+		list_for_each_entry(spu, &cbe_spu_info[lnode].spus, cbe_list) {
+			switch (mode) {
+			case SPU_RESERVE :
+				if ((spu->alloc_state == SPU_FREE) &&
+				    (spu->gang == NULL)) {
+					spu_init_channels(spu);
+					spu->gang = gang;
+					if (++count == gang->contexts)
+						goto spu_get_idle_found;
+				}
+				break;
+			case SPU_RESERVE_UNDO :
+				if ((spu->alloc_state == SPU_FREE) &&
+				    (spu->gang == gang)) {
+					spu->gang = NULL;
+					if (++count == found)
+						goto spu_get_idle_found;
+				}
+				break;
+			}
+		}
+		mutex_unlock(&cbe_spu_info[lnode].list_mutex);
+	}
+	BUG_ON(mode != SPU_RESERVE);
+
+	found = count;
+	ret = -1;
+	mode = SPU_RESERVE_UNDO;
+
+	if (found)
+		goto spu_get_idle_top;
+	else
+		goto spu_get_idle_out;
+
+spu_get_idle_found:
+
+	found = count;
+
+	mutex_unlock(&cbe_spu_info[lnode].list_mutex);
+
+spu_get_idle_out:
+
+	if (ret)
+		spu_gang_nospu_trace(spu_get_idle__not_found,
+					gang, gang->contexts, found)
+	else
+		spu_gang_trace(spu_get_idle__found, gang, gang->contexts)
+
+	return ret;
+}
+
 /**
- * find_victim - find a lower priority context to preempt
- * @ctx:	canidate context for running
+ * find_victim - find a lower priority gang to preempt
+ * @gang:	canidate gang for running
  *
- * Returns the freed physical spu to run the new context on.
+ * Returns 0 for success (preemption occurred), -1 for failure
  */
-static struct spu *find_victim(struct spu_context *ctx)
+static int find_victim(struct spu_gang *gang, int node)
 {
-	struct spu_context *victim = NULL;
+	struct spu_gang *victim;
+	struct spu_context *ctx;
 	struct spu *spu;
-	int node, n;
+	int n, retry = 3;
 
-	spu_context_nospu_trace(spu_find_victim__enter, ctx);
+	spu_context_nospu_trace(spu_find_victim__enter, gang);
+
+	if (node == SPU_PLACE_ALL)
+		node = cpu_to_node(raw_smp_processor_id());
 
-	/*
-	 * Look for a possible preemption candidate on the local node first.
-	 * If there is no candidate look at the other nodes.  This isn't
-	 * exactly fair, but so far the whole spu scheduler tries to keep
-	 * a strong node affinity.  We might want to fine-tune this in
-	 * the future.
-	 */
- restart:
-	node = cpu_to_node(raw_smp_processor_id());
 	for (n = 0; n < MAX_NUMNODES; n++, node++) {
+
 		node = (node < MAX_NUMNODES) ? node : 0;
-		if (!node_allowed(ctx, node))
+		if (!node_allowed(gang, node))
+			continue;
+restart_node:
+		/*
+		 * Retry to avoid algorithm deadlock.  The act of
+		 * unscheduling takes place before scheduling, so we can't
+		 * spin indefinitely in the unschedule (ie. find_victim)
+		 * waiting for a priority change to occur.
+		 */
+		if (!--retry)
 			continue;
 
+		victim = NULL;
+
 		mutex_lock(&cbe_spu_info[node].list_mutex);
 		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
-			struct spu_context *tmp = spu->ctx;
+			struct spu_gang *tmp = spu->gang;
+			struct spu_context *tmpc = spu->ctx;
 
-			if (tmp && tmp->prio > ctx->prio &&
-			    !(tmp->flags & SPU_CREATE_NOSCHED) &&
+			if ((spu->alloc_state == SPU_USED) &&
+			    (tmp != NULL) &&
+			    (tmp->prio > gang->prio) &&
+			   !(tmpc->flags & SPU_CREATE_NOSCHED) &&
 			    (!victim || tmp->prio > victim->prio)) {
-				victim = spu->ctx;
+				victim = tmp;
 			}
 		}
-		if (victim)
-			get_spu_context(victim);
 		mutex_unlock(&cbe_spu_info[node].list_mutex);
 
 		if (victim) {
 			/*
-			 * This nests ctx->state_mutex, but we always lock
+			 * This nests gang->mutex, but we always lock
 			 * higher priority contexts before lower priority
 			 * ones, so this is safe until we introduce
 			 * priority inheritance schemes.
 			 *
-			 * XXX if the highest priority context is locked,
-			 * this can loop a long time.  Might be better to
-			 * look at another context or give up after X retries.
+			 * XXX If victim no longer exists, we are referencing
+			 * stray kernel memory and changing it with the mutex
+			 * lock and subsequent actions.
 			 */
-			if (!mutex_trylock(&victim->state_mutex)) {
-				put_spu_context(victim);
-				victim = NULL;
-				goto restart;
+			if (test_bit(SPU_SCHED_DEACTIVATED, &gang->sched_flags))
+				goto restart_node;
+
+			if (!mutex_trylock(&victim->mutex)) {
+				goto restart_node;
 			}
 
-			spu = victim->spu;
-			if (!spu || victim->prio <= ctx->prio) {
+			if (!spu_gang_runnable(victim)) {
 				/*
 				 * This race can happen because we've dropped
 				 * the active list mutex.  Not a problem, just
 				 * restart the search.
 				 */
-				mutex_unlock(&victim->state_mutex);
-				put_spu_context(victim);
-				victim = NULL;
-				goto restart;
+				mutex_unlock(&victim->mutex);
+				goto restart_node;
 			}
 
-			spu_context_trace(__spu_deactivate__unload, ctx, spu);
+			ctx = list_first_entry(&victim->list,
+					struct spu_context, gang_list);
 
-			mutex_lock(&cbe_spu_info[node].list_mutex);
-			cbe_spu_info[node].nr_active--;
-			spu_unbind_context(spu, victim);
-			mutex_unlock(&cbe_spu_info[node].list_mutex);
+			if (!ctx->spu || victim->prio <= gang->prio) {
+				/*
+				 * This race can happen because we've dropped
+				 * the active list mutex.  Not a problem, just
+				 * restart the search.
+				 */
+				mutex_unlock(&victim->mutex);
+				goto restart_node;
+			}
 
-			victim->stats.invol_ctx_switch++;
-			spu->stats.invol_ctx_switch++;
-			if (test_bit(SPU_SCHED_SPU_RUN, &victim->sched_flags))
-				spu_add_to_rq(victim);
+			spu_gang_trace(__spu_deactivate__unload,
+						victim, victim->contexts);
 
-			mutex_unlock(&victim->state_mutex);
-			put_spu_context(victim);
+			spu_unschedule(victim);
+			spu_add_to_rq(victim);
 
-			return spu;
+			mutex_unlock(&victim->mutex);
+
+			return 0;
 		}
 	}
+	return -1;
+}
 
-	return NULL;
+static int spu_gang_placeable(struct spu_gang *gang,
+	struct spu_sched_stats *stats, int *node_chosen, int *node_preempt)
+{
+	/*
+	 * Strategy is to minimize preemption and to place contexts on
+	 * a single node, if possible.  Affinity gangs must be scheduled
+	 * on one node.  Identify nodes to preempt if necessary.
+	 */
+	if (has_affinity(gang)) {
+		if (stats->inode_icnt + stats->inode_pcnt >= gang->contexts) {
+			*node_chosen = stats->inode;
+			if (stats->inode_icnt < gang->contexts)
+				*node_preempt = stats->inode_icnt;
+			else
+				*node_preempt = SPU_PLACE_NONE;
+			return 1;
+		}
+		if (stats->pnode_icnt + stats->pnode_pcnt >= gang->contexts) {
+			*node_chosen = stats->pnode;
+			if (stats->pnode_icnt < gang->contexts)
+				*node_preempt = stats->pnode;
+			else
+				*node_preempt = SPU_PLACE_NONE;
+			return 1;
+		}
+		return 0;
+	}
+	if (stats->inode_icnt >= gang->contexts) {
+		*node_chosen = stats->inode;	/* allocate idle node */
+		*node_preempt = SPU_PLACE_NONE;
+		return 1;
+	}
+	if (stats->total_icnt >= gang->contexts) {
+		*node_chosen = SPU_PLACE_ALL;	/* allocate all nodes */
+		*node_preempt = SPU_PLACE_NONE;
+		return 1;
+	}
+	if (stats->inode_icnt + stats->inode_pcnt >= gang->contexts) {
+		*node_chosen = stats->inode;	/* allocate idle node */
+		*node_preempt = stats->inode;	/* preempt on idle node */
+		return 1;
+	}
+	if (stats->pnode_icnt + stats->pnode_pcnt >= gang->contexts) {
+		*node_chosen = stats->pnode;	/* allocate other node */
+		*node_preempt = stats->pnode;	/* preempt on other node */
+		return 1;
+	}
+	if (stats->total_icnt + stats->inode_pcnt >= gang->contexts) {
+		*node_chosen = SPU_PLACE_ALL;	/* allocate all nodes */
+		*node_preempt = stats->inode;	/* preempt on idle node */
+		return 1;
+	}
+	if (stats->total_icnt + stats->pnode_pcnt >= gang->contexts) {
+		*node_chosen = SPU_PLACE_ALL;	/* allocate all nodes */
+		*node_preempt = stats->pnode;	/* preempt other node */
+		return 1;
+	}
+	if (stats->total_icnt + stats->total_pcnt >= gang->contexts) {
+		*node_chosen = SPU_PLACE_ALL;	/* allocate nodes */
+		*node_preempt = SPU_PLACE_ALL;	/* preempt all nodes */
+		return 1;
+	}
+	return 0;
 }
 
-static void __spu_schedule(struct spu *spu, struct spu_context *ctx)
+static void spu_get_run_stats(struct spu_gang *gang,
+					struct spu_sched_stats *stats)
 {
-	int node = spu->node;
-	int success = 0;
+	struct spu *spu;
+	int n, node, count_idle, count_preempt;
 
-	spu_set_timeslice(ctx);
+	stats->inode = -1;		/* node with most idle spus */
+	stats->inode_icnt = 0; 		/* n idle on idle node */
+	stats->inode_pcnt = 0;		/* n preemptable on idle node */
+	stats->pnode = -1;		/* node with most preemptable spus */
+	stats->pnode_icnt = 0; 		/* n idle on preempt node */
+	stats->pnode_pcnt = 0; 		/* n preemptable on preempt node */
+	stats->total_icnt = 0; 		/* total idle across all nodes */
+	stats->total_pcnt = 0;		/* total preemptable across all nodes */
 
-	mutex_lock(&cbe_spu_info[node].list_mutex);
-	if (spu->ctx == NULL) {
-		spu_bind_context(spu, ctx);
-		cbe_spu_info[node].nr_active++;
-		spu->alloc_state = SPU_USED;
-		success = 1;
-	}
-	mutex_unlock(&cbe_spu_info[node].list_mutex);
+	node = cpu_to_node(raw_smp_processor_id());
+	for (n = 0; n < MAX_NUMNODES; n++, node++) {
 
-	if (success)
-		wake_up_all(&ctx->run_wq);
-	else
-		spu_add_to_rq(ctx);
-}
+		node = (node < MAX_NUMNODES) ? node : 0;
+		if (!node_allowed(gang, node))
+			continue;
 
-static void spu_schedule(struct spu *spu, struct spu_context *ctx)
-{
-	/* not a candidate for interruptible because it's called either
-	   from the scheduler thread or from spu_deactivate */
-	mutex_lock(&ctx->state_mutex);
-	if (ctx->state == SPU_STATE_SAVED)
-		__spu_schedule(spu, ctx);
-	spu_release(ctx);
+		count_idle = 0;
+		count_preempt = 0;
+
+		mutex_lock(&cbe_spu_info[node].list_mutex);
+		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list) {
+			struct spu_gang *tmp = spu->gang;
+			struct spu_context *tmpc = spu->ctx;
+
+			switch (spu->alloc_state) {
+			case SPU_FREE :
+				if (!tmp)
+					count_idle++;
+				break;
+			case SPU_USED :
+				if (tmpc &&
+				   !(tmpc->flags & SPU_CREATE_NOSCHED)) {
+					if (tmp == gang) /* yield/deactivate */
+						count_idle++;
+					else if (tmp->prio > gang->prio)
+						count_preempt++;
+				}
+				break;
+			}
+		}
+		mutex_unlock(&cbe_spu_info[node].list_mutex);
+
+		if (stats->inode == -1 || stats->inode_icnt < count_idle) {
+			stats->inode_icnt = count_idle;
+			stats->inode_pcnt = count_preempt;
+			stats->inode = node;
+		}
+
+		if (stats->pnode == -1 || stats->pnode_pcnt < count_preempt) {
+			stats->pnode_icnt = count_idle;
+			stats->pnode_pcnt = count_preempt;
+			stats->pnode = node;
+		}
+
+		stats->total_icnt += count_idle;
+		stats->total_pcnt += count_preempt;
+	}
 }
 
-/**
- * spu_unschedule - remove a context from a spu, and possibly release it.
- * @spu:	The SPU to unschedule from
- * @ctx:	The context currently scheduled on the SPU
- * @free_spu	Whether to free the SPU for other contexts
- *
- * Unbinds the context @ctx from the SPU @spu. If @free_spu is non-zero, the
- * SPU is made available for other contexts (ie, may be returned by
- * spu_get_idle). If this is zero, the caller is expected to schedule another
- * context to this spu.
- *
- * Should be called with ctx->state_mutex held.
- */
-static void spu_unschedule(struct spu *spu, struct spu_context *ctx,
-		int free_spu)
+static int spu_gang_schedulable(struct spu_gang *gang,
+		int *node_chosen, int *node_preempt)
 {
-	int node = spu->node;
+	struct spu_sched_stats stats;
+	int ret;
 
-	mutex_lock(&cbe_spu_info[node].list_mutex);
-	cbe_spu_info[node].nr_active--;
-	if (free_spu)
-		spu->alloc_state = SPU_FREE;
-	spu_unbind_context(spu, ctx);
-	ctx->stats.invol_ctx_switch++;
-	spu->stats.invol_ctx_switch++;
-	mutex_unlock(&cbe_spu_info[node].list_mutex);
+	mutex_lock(&spu_prio->runq_lock);
+	spu_get_run_stats(gang, &stats);
+	mutex_unlock(&spu_prio->runq_lock);
+	ret = spu_gang_placeable(gang, &stats, node_chosen, node_preempt);
+	return ret;
 }
 
+
 /**
  * spu_activate - find a free spu for a context and execute it
- * @ctx:	spu context to schedule
- * @flags:	flags (currently ignored)
+ * @ctx:		spu context to schedule
+ * @flags:		flags (currently ignored)
  *
  * Tries to find a free spu to run @ctx.  If no free spu is available
  * add the context to the runqueue so it gets woken up once an spu
@@ -799,100 +998,184 @@ static void spu_unschedule(struct spu *spu, struct spu_context *ctx,
  */
 int spu_activate(struct spu_context *ctx, unsigned long flags)
 {
-	struct spu *spu;
+	struct spu_gang *gang = ctx->gang;
+	int ret, node_chosen, node_preempt;
+
+	if (signal_pending(current))
+		return -ERESTARTSYS;
 
-	/*
-	 * If there are multiple threads waiting for a single context
-	 * only one actually binds the context while the others will
-	 * only be able to acquire the state_mutex once the context
-	 * already is in runnable state.
-	 */
 	if (ctx->spu)
 		return 0;
 
-spu_activate_top:
-	if (signal_pending(current))
-		return -ERESTARTSYS;
+	if (!mutex_trylock(&gang->mutex)) {
+		spu_release(ctx);
+		mutex_lock(&gang->mutex);
+		mutex_lock(&ctx->state_mutex);
+	}
 
-	spu = spu_get_idle(ctx);
 	/*
-	 * If this is a realtime thread we try to get it running by
-	 * preempting a lower priority thread.
+	 * Recheck as we released lock. Context could have been activated
+	 * if it was previously started and sliced.
 	 */
-	if (!spu && rt_prio(ctx->prio))
-		spu = find_victim(ctx);
-	if (spu) {
-		unsigned long runcntl;
-
-		runcntl = ctx->ops->runcntl_read(ctx);
-		__spu_schedule(spu, ctx);
-		if (runcntl & SPU_RUNCNTL_RUNNABLE)
-			spuctx_switch_state(ctx, SPU_UTIL_USER);
-
+	if (ctx->spu) {
+		mutex_unlock(&gang->mutex);
 		return 0;
 	}
 
-	if (ctx->flags & SPU_CREATE_NOSCHED) {
-		spu_prio_wait(ctx);
-		goto spu_activate_top;
+	if (!spu_gang_runnable(gang)) {
+		mutex_unlock(&gang->mutex);
+		if (ctx->flags & SPU_CREATE_NOSCHED) {
+			ret = spufs_wait(ctx->run_wq,
+				ctx->state == SPU_STATE_RUNNABLE);
+			if (unlikely(ret)) {
+				spu_del_from_rq(gang);
+				mutex_lock(&ctx->state_mutex);
+			}
+			return ret;
+		}
+		return 0;
 	}
+	spu_release(ctx);
+
+	/*
+	 * Activation assumes gang is not on the runqueue as it is
+	 * about to be activated. It could be on the runqueue, if it
+	 * were time sliced while executing user mode code.
+	 */
+	spu_del_from_rq(gang);
+
+	clear_bit(SPU_SCHED_DEACTIVATED, &gang->sched_flags);
 
-	spu_add_to_rq(ctx);
+spu_activate_top:
+
+	if (spu_gang_schedulable(gang, &node_chosen, &node_preempt)) {
 
+		if (node_preempt != SPU_PLACE_NONE) {
+			ret = find_victim(gang, node_preempt);
+			if (unlikely(ret))
+				goto spu_activate_rq;
+		}
+
+		ret = spu_get_idle(gang, node_chosen);
+		if (ret)
+			goto spu_activate_top;
+		__spu_schedule(gang, node_chosen);
+	} else {
+
+spu_activate_rq:
+		spu_add_to_rq(gang);
+		if (ctx->flags & SPU_CREATE_NOSCHED) {
+			spu_acquire(ctx);
+			mutex_unlock(&gang->mutex);
+			ret = spufs_wait(ctx->run_wq,
+				ctx->state == SPU_STATE_RUNNABLE);
+			if (unlikely(ret)) {
+				spu_del_from_rq(gang);
+				mutex_lock(&ctx->state_mutex);
+			}
+			return ret;
+		}
+	}
+	mutex_lock(&ctx->state_mutex);
+	mutex_unlock(&gang->mutex);
 	return 0;
 }
 
 /**
- * grab_runnable_context - try to find a runnable context
+ * grab_runnable_gang - try to find a runnable gang
  *
- * Remove the highest priority context on the runqueue and return it
- * to the caller.  Returns %NULL if no runnable context was found.
+ * Remove the highest priority gang on the runqueue and return it
+ * to the caller.  Returns %NULL if no runnable gang was found.
  */
-static struct spu_context *grab_runnable_context(int prio, int node)
+static struct spu_gang *grab_runnable_gang(struct spu_gang *old,
+		int prio, int *node_chosen, int *node_preempt)
 {
+	struct spu_sched_stats stats, lstats;
 	struct spu_context *ctx;
-	int best;
+	struct spu_gang *gang;
+	int ret, best;
 
+	/*
+	 * If old != NULL, then caller is spu_yield or spu_deactivate.  We
+	 * can use idle spus and spus assigned to old.  Else the caller is the
+	 * scheduler thread (time slicer) and we may only use idle spus.  In
+	 * neither case are we allowed to preempt.  Preemption is only done by
+	 * spu_activation which assumes that the gang is not on the runqueue.
+	 * The fact that we are getting the gang from the runqueue implies
+	 * that it has a less favored priority than anything currently
+	 * running. spu_activate does not call this routine.
+	 */
 	mutex_lock(&spu_prio->runq_lock);
+	if (old) {
+		ctx = list_first_entry(&old->list,
+				struct spu_context, gang_list);
+		BUG_ON(!ctx->spu);
+		spu_get_run_stats(old, &stats);
+	}
 	best = find_first_bit(spu_prio->bitmap, prio);
 	while (best < prio) {
 		struct list_head *rq = &spu_prio->runq[best];
 
-		list_for_each_entry(ctx, rq, rq) {
-			/* XXX(hch): check for affinity here aswell */
-			if (__node_allowed(ctx, node)) {
-				__spu_del_from_rq(ctx);
+		list_for_each_entry(gang, rq, rq) {
+			if (old) {
+				lstats = stats;
+				if (!node_allowed(gang, lstats.inode))
+					lstats.inode_icnt = 0;
+			} else {
+				spu_get_run_stats(gang, &lstats);
+			}
+			ret = spu_gang_placeable(gang, &lstats,
+						node_chosen, node_preempt);
+			if (ret && (*node_preempt == SPU_PLACE_NONE)) {
+				__spu_del_from_rq(gang);
 				goto found;
 			}
 		}
 		best++;
 	}
-	ctx = NULL;
- found:
+	gang = NULL;
+found:
 	mutex_unlock(&spu_prio->runq_lock);
-	return ctx;
+	return gang;
 }
 
-static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio)
+static int __spu_deactivate(struct spu_gang *gang, int force, int max_prio)
 {
-	struct spu *spu = ctx->spu;
-	struct spu_context *new = NULL;
+	struct spu_gang *new;
+	struct spu_context *ctx;
+	int ret, node_chosen, node_preempt;
 
-	if (spu) {
-		new = grab_runnable_context(max_prio, spu->node);
-		if (new || force) {
-			spu_unschedule(spu, ctx, new == NULL);
-			if (new) {
-				if (new->flags & SPU_CREATE_NOSCHED)
-					wake_up(&new->stop_wq);
-				else {
-					spu_release(ctx);
-					spu_schedule(spu, new);
-					/* this one can't easily be made
-					   interruptible */
-					mutex_lock(&ctx->state_mutex);
-				}
+	ctx = list_first_entry(&gang->list, struct spu_context, gang_list);
+	if (!ctx->spu)
+		return 0;
+
+	new = grab_runnable_gang(gang, max_prio, &node_chosen, &node_preempt);
+	if (new || force) {
+		spu_unschedule(gang);
+		if (new) {
+			/*
+			 * None of these locks can be easily made interruptible
+			 */
+			mutex_unlock(&gang->mutex);
+
+			/*
+			 * Schedule gang taken from runqueue.  Should fit, but
+			 * might not as we dropped the lock above.  Also, it
+			 * could have been activated by spu_run.
+			 */
+			mutex_lock(&new->mutex);
+			ctx = list_first_entry(&new->list,
+				struct spu_context, gang_list);
+			if (!ctx->spu) {
+				ret = spu_get_idle(new, node_chosen);
+				if (ret)
+					spu_add_to_rq(new);
+				else
+					__spu_schedule(new, node_chosen);
 			}
+			mutex_unlock(&new->mutex);
+
+			mutex_lock(&gang->mutex);
 		}
 	}
 
@@ -906,67 +1189,85 @@ static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio)
  * Unbind @ctx from the physical spu it is running on and schedule
  * the highest priority context to run on the freed physical spu.
  */
-void spu_deactivate(struct spu_context *ctx)
+void spu_deactivate(struct spu_gang *gang)
 {
-	spu_context_nospu_trace(spu_deactivate__enter, ctx);
-	__spu_deactivate(ctx, 1, MAX_PRIO);
+	spu_context_nospu_trace(spu_deactivate__enter, gang);
+	set_bit(SPU_SCHED_DEACTIVATED, &gang->sched_flags);
+	__spu_deactivate(gang, 1, MAX_PRIO);
+	spu_del_from_rq(gang);
 }
 
 /**
  * spu_yield -	yield a physical spu if others are waiting
  * @ctx:	spu context to yield
  *
- * Check if there is a higher priority context waiting and if yes
- * unbind @ctx from the physical spu and schedule the highest
- * priority context to run on the freed physical spu instead.
+ * Check if there is a higher priority gang waiting and if yes
+ * unbind @ctx and any other within the same gang freeing one or
+ * more physical spus and schedule the highest priority gang
+ * to run on the freed physical spu(s) instead.  The gang is added
+ * back to the runqueue, so that it may be resumed by the scheduler
+ * as soon as there are idle spus.
  */
 void spu_yield(struct spu_context *ctx)
 {
-	spu_context_nospu_trace(spu_yield__enter, ctx);
+	struct spu_gang *gang = ctx->gang;
+	int ret;
+
+	spu_context_nospu_trace(spu_yield__enter, gang);
 	if (!(ctx->flags & SPU_CREATE_NOSCHED)) {
-		mutex_lock(&ctx->state_mutex);
-		__spu_deactivate(ctx, 0, MAX_PRIO);
-		mutex_unlock(&ctx->state_mutex);
+		mutex_lock(&gang->mutex);
+		ret = __spu_deactivate(gang, 0, MAX_PRIO);
+		if (ret)
+			spu_add_to_rq(gang);
+		mutex_unlock(&gang->mutex);
 	}
 }
 
-static noinline void spusched_tick(struct spu_context *ctx)
+static noinline int spusched_tick(struct spu_gang *gang,
+					struct spu_context *ctx,
+					int preempt)
 {
-	struct spu_context *new = NULL;
-	struct spu *spu = NULL;
+	int best, yield;
+	int npreempted = 0;
 
-	if (spu_acquire(ctx))
-		BUG();	/* a kernel thread never has signals pending */
+	if (test_bit(SPU_SCHED_DEACTIVATED, &gang->sched_flags))
+		return 0;
 
-	if (ctx->state != SPU_STATE_RUNNABLE)
-		goto out;
-	if (ctx->flags & SPU_CREATE_NOSCHED)
-		goto out;
-	if (ctx->policy == SCHED_FIFO)
-		goto out;
+	mutex_lock(&gang->mutex);
 
-	if (--ctx->time_slice && test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
-		goto out;
+	BUG_ON(!spu_gang_runnable(gang));
 
-	spu = ctx->spu;
+	if (!ctx->spu)
+		goto out;
 
-	spu_context_trace(spusched_tick__preempt, ctx, spu);
+	if (ctx->flags & SPU_CREATE_NOSCHED)
+		goto out;
 
-	new = grab_runnable_context(ctx->prio + 1, spu->node);
-	if (new) {
-		spu_unschedule(spu, ctx, 0);
-		if (test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
-			spu_add_to_rq(ctx);
-	} else {
+	/*
+	 * If nrunnable is zero, then all of the contexts are in user mode.
+	 */
+	yield = !atomic_read(&gang->nrunnable);
+
+	if (yield || ((ctx->policy != SCHED_FIFO) && (!--ctx->time_slice))) {
+		if (spu_prio->nr_waiting) {
+			best = find_first_bit(spu_prio->bitmap, gang->prio);
+			if (yield || (preempt && best <= gang->prio)) {
+				spu_context_trace(spusched_tick__preempt,
+							ctx, ctx->spu);
+				npreempted = gang->contexts;
+				spu_unschedule(gang);
+				spu_add_to_rq(gang);
+				goto out;
+			}
+		}
 		spu_context_nospu_trace(spusched_tick__newslice, ctx);
-		if (!ctx->time_slice)
+		if (ctx->policy != SCHED_FIFO)
 			ctx->time_slice++;
 	}
 out:
-	spu_release(ctx);
+	mutex_unlock(&gang->mutex);
 
-	if (new)
-		spu_schedule(spu, new);
+	return npreempted;
 }
 
 /**
@@ -1019,30 +1320,104 @@ static void spuloadavg_wake(unsigned long data)
 
 static int spusched_thread(void *unused)
 {
+	struct spu_gang *gang;
+	struct spu_context *ctx;
 	struct spu *spu;
-	int node;
+	int node, active, pnode, preempted, maxcontexts, retry, deactivated;
 
 	while (!kthread_should_stop()) {
 		set_current_state(TASK_INTERRUPTIBLE);
 		schedule();
-		for (node = 0; node < MAX_NUMNODES; node++) {
+
+		/*
+		 * Try to limit the number of context switches because
+		 * we preempt all of the contexts first and then place
+		 * them.  We preempt first as the next gang to run may
+		 * not fit.  Also, it helps us place NUMA and SPU affinity
+		 * jobs as they have special requirements.  Not that we
+		 * are doing that now, but we could. The downside is
+		 * that we will have a little more idle time.  What we
+		 * want to avoid is preempting and then rescheduling
+		 * the same job as it creates hicups in the execution.
+		 */
+		maxcontexts = spu_prio->nr_contexts;
+		preempted = 0;
+
+		/*
+		 * Time slice contexts first assuming that there are
+		 * spe jobs waiting to run.  The next gang to be scheduled
+		 * is of indeterminate size, so it is not sufficient to
+		 * follow the traditional mode which assumes a 1:1
+		 * replacement (1 spu : 1 spe context).
+		 */
+		for (node = 0, active = 0; node < MAX_NUMNODES; node++) {
 			struct mutex *mtx = &cbe_spu_info[node].list_mutex;
 
 			mutex_lock(mtx);
 			list_for_each_entry(spu, &cbe_spu_info[node].spus,
 					cbe_list) {
-				struct spu_context *ctx = spu->ctx;
-
-				if (ctx) {
+				if (spu->alloc_state == SPU_USED) {
+					gang = spu->gang;
+					BUG_ON(!gang);
+					ctx = spu->ctx;
 					get_spu_context(ctx);
 					mutex_unlock(mtx);
-					spusched_tick(ctx);
+					preempted += spusched_tick(gang, ctx,
+						preempted < maxcontexts);
 					mutex_lock(mtx);
 					put_spu_context(ctx);
+					active++;
 				}
 			}
 			mutex_unlock(mtx);
 		}
+
+		spu_sched_stats(spusched_thread__timeslice,
+					maxcontexts, active, preempted);
+
+		/*
+		 * Place as many gangs as possible.  A gang might fail to
+		 * be placed if it has NUMA bindings, SPU Affinity, or is
+		 * to big to fit.  On failure, the gang is added to the
+		 * back of the runqueue, which effectively allows us to
+		 * skip over a job, assuming it is not the only one at a
+		 * given priority level.
+		 */
+		retry = 0;
+		active = 0;
+		while (retry < maxcontexts) {
+
+			gang = grab_runnable_gang(NULL, MAX_PRIO,
+					&node, &pnode);
+			if (!gang)
+				break;
+
+			/*
+			 * Must recheck state as we have dropped all locks.
+			 * It could be running, deactivated, or destroyed. The
+			 * latter is still a problem. See find_victim (XXX).
+			 */
+			deactivated = test_bit(SPU_SCHED_DEACTIVATED,
+						&gang->sched_flags);
+			if (!deactivated) {
+				mutex_lock(&gang->mutex);
+				ctx = list_first_entry(&gang->list,
+					struct spu_context, gang_list);
+				if (!ctx->spu) {
+					if (spu_get_idle(gang, node)) {
+						spu_add_to_rq(gang);
+						retry++;
+					} else {
+						__spu_schedule(gang, node);
+						active++;
+					}
+				}
+				mutex_unlock(&gang->mutex);
+			}
+		}
+
+		spu_sched_stats(spusched_thread__scheduled,
+				spu_prio->nr_contexts, active, retry);
 	}
 
 	return 0;
@@ -1180,8 +1555,10 @@ void spu_sched_exit(void)
 	for (node = 0; node < MAX_NUMNODES; node++) {
 		mutex_lock(&cbe_spu_info[node].list_mutex);
 		list_for_each_entry(spu, &cbe_spu_info[node].spus, cbe_list)
-			if (spu->alloc_state != SPU_FREE)
+			if (spu->alloc_state != SPU_FREE) {
 				spu->alloc_state = SPU_FREE;
+				spu->gang = NULL;
+			}
 		mutex_unlock(&cbe_spu_info[node].list_mutex);
 	}
 	kfree(spu_prio);
diff --git a/arch/powerpc/platforms/cell/spufs/spufs.h b/arch/powerpc/platforms/cell/spufs/spufs.h
index a8f5203..8e84481 100644
--- a/arch/powerpc/platforms/cell/spufs/spufs.h
+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -47,11 +47,12 @@ enum {
 struct spu_context_ops;
 struct spu_gang;
 
-/* ctx->sched_flags */
+/* ctx->sched_flags and gang->sched_flags */
 enum {
 	SPU_SCHED_NOTIFY_ACTIVE,
-	SPU_SCHED_WAS_ACTIVE,	/* was active upon spu_acquire_saved()  */
 	SPU_SCHED_SPU_RUN,	/* context is within spu_run */
+	SPU_SCHED_JUST_CREATED,	/* context created but not started */
+	SPU_SCHED_DEACTIVATED,	/* gang has been deactivated */
 };
 
 enum {
@@ -121,7 +122,6 @@ struct spu_context {
 	pid_t tid;
 
 	/* scheduler fields */
-	struct list_head rq;
 	unsigned int time_slice;
 	unsigned long sched_flags;
 	cpumask_t cpus_allowed;
@@ -165,7 +165,12 @@ struct spu_gang {
 	cpumask_t cpus_allowed;
 	int policy;
 	int prio;
+	atomic_t nstarted;
+	atomic_t nrunnable;
+	unsigned long sched_flags;
+	struct list_head rq;
 
+	/* spu scheduler affinity fields */
 	struct spu_context *aff_ref_ctx;
 	struct list_head aff_list_head;
 	struct mutex aff_mutex;
@@ -174,6 +179,11 @@ struct spu_gang {
 	atomic_t aff_sched_count;
 };
 
+static inline int spu_gang_runnable(struct spu_gang *g)
+{
+	return (g->contexts && (atomic_read(&g->nstarted) == g->contexts));
+}
+
 /* Flag bits for spu_gang aff_flags */
 #define AFF_OFFSETS_SET		1
 #define AFF_MERGED		2
@@ -298,9 +308,8 @@ int __must_check spu_acquire_saved(struct spu_context *ctx);
 void spu_release_saved(struct spu_context *ctx);
 
 int spu_stopped(struct spu_context *ctx, u32 * stat);
-void spu_del_from_rq(struct spu_context *ctx);
 int spu_activate(struct spu_context *ctx, unsigned long flags);
-void spu_deactivate(struct spu_context *ctx);
+void spu_deactivate(struct spu_gang *gang);
 void spu_yield(struct spu_context *ctx);
 void spu_switch_notify(struct spu *spu, struct spu_context *ctx);
 void spu_switch_log_notify(struct spu *spu, struct spu_context *ctx,
@@ -377,6 +386,12 @@ extern void spu_free_lscsa(struct spu_state *csa);
 extern void spuctx_switch_state(struct spu_context *ctx,
 		enum spu_utilization_state new_state);
 
+#define spu_sched_stats(name, maxcontexts, active, preempted) \
+	trace_mark(name, "%d %d %d", maxcontexts, active, preempted);
+#define spu_gang_trace(name, gang, cnt) \
+	trace_mark(name, "%p %d", gang, cnt);
+#define spu_gang_nospu_trace(name, gang, cnt, found) \
+	trace_mark(name, "%p %d %d", gang, cnt, found);
 #define spu_context_trace(name, ctx, spu) \
 	trace_mark(name, "ctx %p spu %p", ctx, spu);
 #define spu_context_nospu_trace(name, ctx) \
