Date: Fri, 20 Oct 2006 14:56:01 +0100 (BST)
From: Daniel Drake <ddrake@brontes3d.com>
Subject: video1394: remove BKL contention

video1394 does not need to take the BKL. The data structures shared between
file_operations and interrupts are already protected through context-specific
spinlocks.

The only other danger is video1394_release() being called during another
operation, however this cannot happen because release is only ever invoked
when the last thread has closed the fd.

Signed-off-by: Daniel Drake <ddrake@brontes3d.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---
Index: linux/drivers/ieee1394/video1394.c
===================================================================
--- linux.orig/drivers/ieee1394/video1394.c
+++ linux/drivers/ieee1394/video1394.c
@@ -714,8 +714,8 @@ static inline unsigned video1394_buffer_
 	return ret;
 }
 
-static int __video1394_ioctl(struct file *file,
-			     unsigned int cmd, unsigned long arg)
+static long video1394_ioctl(struct file *file,
+			    unsigned int cmd, unsigned long arg)
 {
 	struct file_ctx *ctx = (struct file_ctx *)file->private_data;
 	struct ti_ohci *ohci = ctx->ohci;
@@ -1158,15 +1158,6 @@ static int __video1394_ioctl(struct file
 	}
 }
 
-static long video1394_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
-{
-	int err;
-	lock_kernel();
-	err = __video1394_ioctl(file, cmd, arg);
-	unlock_kernel();
-	return err;
-}
-
 /*
  *	This maps the vmalloced and reserved buffer to user space.
  *
@@ -1179,17 +1170,14 @@ static long video1394_ioctl(struct file 
 static int video1394_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct file_ctx *ctx = (struct file_ctx *)file->private_data;
-	int res = -EINVAL;
 
-	lock_kernel();
 	if (ctx->current_ctx == NULL) {
 		PRINT(KERN_ERR, ctx->ohci->host->id,
 				"Current iso context not set");
-	} else
-		res = dma_region_mmap(&ctx->current_ctx->dma, file, vma);
-	unlock_kernel();
+		return -EINVAL;
+	}
 
-	return res;
+	return dma_region_mmap(&ctx->current_ctx->dma, file, vma);
 }
 
 static unsigned int video1394_poll(struct file *file, poll_table *pt)
@@ -1200,14 +1188,12 @@ static unsigned int video1394_poll(struc
 	struct dma_iso_ctx *d;
 	int i;
 
-	lock_kernel();
 	ctx = file->private_data;
 	d = ctx->current_ctx;
 	if (d == NULL) {
 		PRINT(KERN_ERR, ctx->ohci->host->id,
 				"Current iso context not set");
-		mask = POLLERR;
-		goto done;
+		return POLLERR;
 	}
 
 	poll_wait(file, &d->waitq, pt);
@@ -1220,8 +1206,6 @@ static unsigned int video1394_poll(struc
 		}
 	}
 	spin_unlock_irqrestore(&d->lock, flags);
-done:
-	unlock_kernel();
 
 	return mask;
 }
@@ -1257,7 +1241,6 @@ static int video1394_release(struct inod
 	struct list_head *lh, *next;
 	u64 mask;
 
-	lock_kernel();
 	list_for_each_safe(lh, next, &ctx->context_list) {
 		struct dma_iso_ctx *d;
 		d = list_entry(lh, struct dma_iso_ctx, link);
@@ -1278,7 +1261,6 @@ static int video1394_release(struct inod
 	kfree(ctx);
 	file->private_data = NULL;
 
-	unlock_kernel();
 	return 0;
 }