Subject: Re: [PATCH] RTAS - adapt procfs interface

From: Nathan Lynch <[email-masked]>
Date: Tue, 1 Apr 2008 15:04:04 -0500

Nathan Lynch wrote:
> 
> One could argue that the real problem is using the proc_dir_entry's
> reference count to enforce exclusive open.

I think this is better... the way these files are used is lame, but
this should preserve the existing behavior.  I haven't yet tested
this, can you?

diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
index f227659..00bc308 100644
--- a/arch/powerpc/kernel/rtas_flash.c
+++ b/arch/powerpc/kernel/rtas_flash.c
@@ -139,7 +139,7 @@ struct rtas_validate_flash_t
 	unsigned int update_results;	/* Update results token */
 };
 
-static DEFINE_SPINLOCK(flash_file_open_lock);
+static atomic_t open_count = ATOMIC_INIT(0);
 static struct proc_dir_entry *firmware_flash_pde;
 static struct proc_dir_entry *firmware_update_pde;
 static struct proc_dir_entry *validate_pde;
@@ -216,7 +216,7 @@ static int rtas_flash_release(struct inode *inode, struct file *file)
 		uf->flist = NULL;
 	}
 
-	atomic_dec(&dp->count);
+	atomic_dec(&open_count);
 	return 0;
 }
 
@@ -352,26 +352,17 @@ static ssize_t rtas_flash_write(struct file *file, const char __user *buffer,
 
 static int rtas_excl_open(struct inode *inode, struct file *file)
 {
-	struct proc_dir_entry *dp = PDE(inode);
-
-	/* Enforce exclusive open with use count of PDE */
-	spin_lock(&flash_file_open_lock);
-	if (atomic_read(&dp->count) > 1) {
-		spin_unlock(&flash_file_open_lock);
+	if (atomic_inc_return(&open_count) > 1) {
+		atomic_dec(&open_count);
 		return -EBUSY;
 	}
 
-	atomic_inc(&dp->count);
-	spin_unlock(&flash_file_open_lock);
-	
 	return 0;
 }
 
 static int rtas_excl_release(struct inode *inode, struct file *file)
 {
-	struct proc_dir_entry *dp = PDE(inode);
-
-	atomic_dec(&dp->count);
+	atomic_dec(&open_count);
 
 	return 0;
 }
@@ -580,7 +571,7 @@ static int validate_flash_release(struct inode *inode, struct file *file)
 	}
 
 	/* The matching atomic_inc was in rtas_excl_open() */
-	atomic_dec(&dp->count);
+	atomic_dec(&open_count);
 
 	return 0;
 }