Commit 205153aa authored Oct 09, 2009 by Frederic Weisbecker Committed by Thomas Gleixner Oct 14, 2009

mem_class: Drop the bkl from memory_open()



The generic open callback for the mem class devices is "protected" by
the bkl.

Let's look at the datas manipulated inside memory_open:

- inode and file: safe
- the devlist: safe because it is constant
- the memdev classes inside this array are safe too (constant)

After we find out which memdev file operation we need to use, we call
its open callback. Depending on the targeted memdev, we call either
open_port() that doesn't manipulate any racy data (just a capable()
check), or we call nothing.

So it's safe to remove the big kernel lock there.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1255113062-5835-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 4c2aedc2

drivers/char/mem.c

+5 −12

Original line number	Diff line number	Diff line
		@@ -26,7 +26,6 @@
		#include <linux/bootmem.h>
		#include <linux/splice.h>
		#include <linux/pfn.h>
		#include <linux/smp_lock.h>

		#include <asm/uaccess.h>
		#include <asm/io.h>
		@@ -892,29 +891,23 @@ static int memory_open(struct inode inode, struct file filp)
		{
		int minor;
		const struct memdev *dev;
		int ret = -ENXIO;

		lock_kernel();

		minor = iminor(inode);
		if (minor >= ARRAY_SIZE(devlist))
		goto out;
		return -ENXIO;

		dev = &devlist[minor];
		if (!dev->fops)
		goto out;
		return -ENXIO;

		filp->f_op = dev->fops;
		if (dev->dev_info)
		filp->f_mapping->backing_dev_info = dev->dev_info;

		if (dev->fops->open)
		ret = dev->fops->open(inode, filp);
		else
		ret = 0;
		out:
		unlock_kernel();
		return ret;
		return dev->fops->open(inode, filp);

		return 0;
		}

		static const struct file_operations memory_fops = {

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