[POWERPC] spufs: fix rescheduling of non-runnable contexts

At present, we can hit the BUG_ON in __spu_update_sched_info by reading
the regs file of a context between two calls to spu_run. The
spu_release_saved called by spufs_regs_read() is resulting in the (now
non-runnable) context being placed back on the run queue, so the next
call to spu_run ends up in the bug condition.

This change uses the SPU_SCHED_SPU_RUN flag to only reschedule a context
if it's still in spu_run().

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

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

@@ -170,7 +170,8 @@ void spu_release_saved(struct spu_context *ctx)
 {
 	BUG_ON(ctx->state != SPU_STATE_SAVED);
 
-	if (test_and_clear_bit(SPU_SCHED_WAS_ACTIVE, &ctx->sched_flags))
+	if (test_and_clear_bit(SPU_SCHED_WAS_ACTIVE, &ctx->sched_flags) &&
+			test_bit(SPU_SCHED_SPU_RUN, &ctx->sched_flags))
 		spu_activate(ctx, 0);
 
 	spu_release(ctx);