Subject: spufs: state_mutex cleanup

From: Christoph Hellwig <hch@lst.de>
Various cleanups in code surrounding the state semaphore:

 - inline spu_acquire/spu_release
 - cleanup spu_acquire_* and add kerneldoc comments to these functions
 - remove spu_release_exclusive and replace it with spu_release

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>

Index: linux-2.6/arch/powerpc/platforms/cell/spufs/context.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/context.c
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/context.c
@@ -96,16 +96,6 @@ void spu_forget(struct spu_context *ctx)
 	spu_release(ctx);
 }
 
-void spu_acquire(struct spu_context *ctx)
-{
-	mutex_lock(&ctx->state_mutex);
-}
-
-void spu_release(struct spu_context *ctx)
-{
-	mutex_unlock(&ctx->state_mutex);
-}
-
 void spu_unmap_mappings(struct spu_context *ctx)
 {
 	if (ctx->local_store)
@@ -120,66 +110,85 @@ void spu_unmap_mappings(struct spu_conte
 		unmap_mapping_range(ctx->signal2, 0, 0x4000, 1);
 }
 
+/**
+ * spu_acquire_exclusive - lock spu contex and protect against userspace access
+ * @ctx:	spu contex to lock
+ *
+ * Note:
+ *	Returns 0 and with the context locked on success
+ *	Returns negative error and with the context _unlocked_ on failure.
+ */
 int spu_acquire_exclusive(struct spu_context *ctx)
 {
-	int ret = 0;
+	int ret = -EINVAL;
 
-	mutex_lock(&ctx->state_mutex);
-	/* ctx is about to be freed, can't acquire any more */
-	if (!ctx->owner) {
-		ret = -EINVAL;
-		goto out;
-	}
+	spu_acquire(ctx);
+	/*
+	 * Context is about to be freed, so we can't acquire it anymore.
+	 */
+	if (!ctx->owner)
+		goto out_unlock;
 
 	if (ctx->state == SPU_STATE_SAVED) {
 		ret = spu_activate(ctx, 0);
 		if (ret)
-			goto out;
+			goto out_unlock;
 	} else {
-		/* We need to exclude userspace access to the context. */
+		/*
+		 * We need to exclude userspace access to the context.
+		 *
+		 * To protect against memory access we invalidate all ptes
+		 * and make sure the pagefault handlers block on the mutex.
+		 */
 		spu_unmap_mappings(ctx);
 	}
 
-out:
-	if (ret)
-		mutex_unlock(&ctx->state_mutex);
+	return 0;
+
+ out_unlock:
+	spu_release(ctx);
 	return ret;
 }
 
+/**
+ * spu_acquire_runnable - lock spu contex and make sure it is in runnable state
+ * @ctx:	spu contex to lock
+ *
+ * Note:
+ *	Returns 0 and with the context locked on success
+ *	Returns negative error and with the context _unlocked_ on failure.
+ */
 int spu_acquire_runnable(struct spu_context *ctx)
 {
-	int ret = 0;
-
-	mutex_lock(&ctx->state_mutex);
-	if (ctx->state == SPU_STATE_RUNNABLE) {
-		ctx->spu->prio = current->prio;
-		return 0;
-	}
-
-	/* ctx is about to be freed, can't acquire any more */
-	if (!ctx->owner) {
-		ret = -EINVAL;
-		goto out;
-	}
+	int ret = -EINVAL;
 
+	spu_acquire(ctx);
 	if (ctx->state == SPU_STATE_SAVED) {
+		/*
+		 * Context is about to be freed, so we can't acquire it anymore.
+		 */
+		if (!ctx->owner)
+			goto out_unlock;
 		ret = spu_activate(ctx, 0);
 		if (ret)
-			goto out;
-	}
+			goto out_unlock;
+	} else
+		ctx->spu->prio = current->prio;
 
-	/* On success, we return holding the lock */
-	return ret;
-out:
-	/* Release here, to simplify calling code. */
-	mutex_unlock(&ctx->state_mutex);
+	return 0;
 
+ out_unlock:
+	spu_release(ctx);
 	return ret;
 }
 
+/**
+ * spu_acquire_saved - lock spu contex and make sure it is in saved state
+ * @ctx:	spu contex to lock
+ */
 void spu_acquire_saved(struct spu_context *ctx)
 {
-	mutex_lock(&ctx->state_mutex);
-	if (ctx->state == SPU_STATE_RUNNABLE)
+	spu_acquire(ctx);
+	if (ctx->state != SPU_STATE_SAVED)
 		spu_deactivate(ctx);
 }
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/spufs.h
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/spufs.h
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -156,6 +156,16 @@ void spu_gang_remove_ctx(struct spu_gang
 void spu_gang_add_ctx(struct spu_gang *gang, struct spu_context *ctx);
 
 /* context management */
+static inline void spu_acquire(struct spu_context *ctx)
+{
+	mutex_lock(&ctx->state_mutex);
+}
+
+static inline void spu_release(struct spu_context *ctx)
+{
+	mutex_unlock(&ctx->state_mutex);
+}
+
 struct spu_context * alloc_spu_context(struct spu_gang *gang);
 void destroy_spu_context(struct kref *kref);
 struct spu_context * get_spu_context(struct spu_context *ctx);
@@ -163,17 +173,9 @@ int put_spu_context(struct spu_context *
 void spu_unmap_mappings(struct spu_context *ctx);
 
 void spu_forget(struct spu_context *ctx);
-void spu_acquire(struct spu_context *ctx);
-void spu_release(struct spu_context *ctx);
 int spu_acquire_runnable(struct spu_context *ctx);
 void spu_acquire_saved(struct spu_context *ctx);
 int spu_acquire_exclusive(struct spu_context *ctx);
-
-static inline void spu_release_exclusive(struct spu_context *ctx)
-{
-	mutex_unlock(&ctx->state_mutex);
-}
-
 int spu_activate(struct spu_context *ctx, u64 flags);
 void spu_deactivate(struct spu_context *ctx);
 void spu_yield(struct spu_context *ctx);
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/run.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/run.c
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/run.c
@@ -133,7 +133,7 @@ out_drop_priv:
 	spu_mfc_sr1_set(ctx->spu, sr1);
 
 out_unlock:
-	spu_release_exclusive(ctx);
+	spu_release(ctx);
 out:
 	return ret;
 }