[PATCH] spufs: serialize sys_spu_run per spu

During an earlier cleanup, we lost the serialization
of multiple spu_run calls performed on the same
spu_context. In order to get this back, introduce a
mutex in the spu_context that is held inside of spu_run.

Noticed by Al Viro.

Signed-off-by: Arnd Bergmann <arndb@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 12 insertions, 5 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/context.c b/arch/powerpc/platforms/cell/spufs/context.c
index 903c35d19577..c5cd55ac848d 100644
--- a/arch/powerpc/platforms/cell/spufs/context.c
+++ b/arch/powerpc/platforms/cell/spufs/context.c
@@ -43,6 +43,7 @@ struct spu_context *alloc_spu_context(struct address_space *local_store)
         spin_lock_init(&ctx->mmio_lock);
         kref_init(&ctx->kref);
         init_rwsem(&ctx->state_sema);
+        init_MUTEX(&ctx->run_sema);
         init_waitqueue_head(&ctx->ibox_wq);
         init_waitqueue_head(&ctx->wbox_wq);
         init_waitqueue_head(&ctx->stop_wq);
diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index 9738de727f32..e63426822fd5 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -620,8 +620,12 @@ long spufs_run_spu(struct file *file, struct spu_context *ctx,
 {
         int ret;
 
-        if ((ret = spu_run_init(ctx, npc, status)) != 0)
-                return ret;
+        if (down_interruptible(&ctx->run_sema))
+                return -ERESTARTSYS;
+
+        ret = spu_run_init(ctx, npc, status);
+        if (ret)
+                goto out;
 
         do {
                 ret = spufs_wait(ctx->stop_wq, spu_stopped(ctx, status));
@@ -629,9 +633,8 @@ long spufs_run_spu(struct file *file, struct spu_context *ctx,
                         break;
                 if (unlikely(ctx->state != SPU_STATE_RUNNABLE)) {
                         ret = spu_reacquire_runnable(ctx, npc, status);
-                        if (ret) {
-                                return ret;
-                        }
+                        if (ret)
+                                goto out;
                         continue;
                 }
                 ret = spu_process_events(ctx);
@@ -645,6 +648,8 @@ long spufs_run_spu(struct file *file, struct spu_context *ctx,
                 ret = *status;
         spu_yield(ctx);
 
+out:
+        up(&ctx->run_sema);
         return ret;
 }
 
diff --git a/arch/powerpc/platforms/cell/spufs/spufs.h b/arch/powerpc/platforms/cell/spufs/spufs.h
index 420953b58881..b50474450819 100644
--- a/arch/powerpc/platforms/cell/spufs/spufs.h
+++ b/arch/powerpc/platforms/cell/spufs/spufs.h
@@ -48,6 +48,7 @@ struct spu_context {
 
         enum { SPU_STATE_RUNNABLE, SPU_STATE_SAVED } state;
         struct rw_semaphore state_sema;
+        struct semaphore run_sema;
 
         struct mm_struct *owner;