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Date: Fri, 18 Apr 2008 21:45:21 -0400
From: Andres Salomon <dilinger@...ued.net>
To: Thiago Galesi <thiagogalesi@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
linux-fbdev-devel@...ts.sourceforge.net
Subject: Re: [Linux-fbdev-devel] [PATCH] fb: Remove use of lock_kernel /
unlock_kernel in fbmem
On Fri, 18 Apr 2008 21:54:43 -0300
Thiago Galesi <thiagogalesi@...il.com> wrote:
> Hello
>
>
> >Just a minor nit; in general, I'd think you would want to completely
> >initialize the structure (including calling mutex_init) before
> >registering the structure with the rest of the system (in this case,
> >with registered_fb and *_call_notifier_chain). Initializing after
> >registration is just asking for a race conditions.
>
> This is better??
That does look better, yes. Someone else who is familiar w/ the locking
semantics there would have to comment on the rest of it.
>
>
> ---
> This patch removes lock_kernel(), unlock_kernel() usage in fbmem.c and replaces it with a mutex
>
> Signed-off-by: Thiago Galesi <thiagogalesi@...il.com>
>
> ---
>
>
> Index: linux-2.6.23.1/drivers/video/fbmem.c
> ===================================================================
> --- linux-2.6.23.1.orig/drivers/video/fbmem.c 2008-04-16 18:52:32.000000000 -0300
> +++ linux-2.6.23.1/drivers/video/fbmem.c 2008-04-18 19:25:53.000000000 -0300
> @@ -987,7 +987,7 @@
> }
>
> static int
> -fb_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
> +__fb_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
> unsigned long arg)
> {
> int fbidx = iminor(inode);
> @@ -1085,6 +1085,28 @@
> }
> }
>
> +static int
> +fb_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + int fbidx = iminor(inode);
> + struct fb_info *info = registered_fb[fbidx];
> + int ret;
> +
> + mutex_lock(&info->hwlock);
> + ret = __fb_ioctl(inode, file, cmd, arg);
> + mutex_unlock(&info->hwlock);
> + return ret;
> +}
> +
> +static long
> +fb_unlocked_ioctl(struct file *file, unsigned int cmd,
> + unsigned long arg)
> +{
> + struct inode *inode = file->f_path.dentry->d_inode;
> + return fb_ioctl(inode, file, cmd, arg);
> +}
> +
> #ifdef CONFIG_COMPAT
> struct fb_fix_screeninfo32 {
> char id[16];
> @@ -1136,7 +1158,7 @@
> put_user(compat_ptr(data), &cmap->transp))
> return -EFAULT;
>
> - err = fb_ioctl(inode, file, cmd, (unsigned long) cmap);
> + err = __fb_ioctl(inode, file, cmd, (unsigned long) cmap);
>
> if (!err) {
> if (copy_in_user(&cmap32->start,
> @@ -1190,7 +1212,7 @@
>
> old_fs = get_fs();
> set_fs(KERNEL_DS);
> - err = fb_ioctl(inode, file, cmd, (unsigned long) &fix);
> + err = __fb_ioctl(inode, file, cmd, (unsigned long) &fix);
> set_fs(old_fs);
>
> if (!err)
> @@ -1208,7 +1230,7 @@
> struct fb_ops *fb = info->fbops;
> long ret = -ENOIOCTLCMD;
>
> - lock_kernel();
> + mutex_lock(&info->hwlock);
> switch(cmd) {
> case FBIOGET_VSCREENINFO:
> case FBIOPUT_VSCREENINFO:
> @@ -1217,7 +1239,7 @@
> case FBIOPUT_CON2FBMAP:
> arg = (unsigned long) compat_ptr(arg);
> case FBIOBLANK:
> - ret = fb_ioctl(inode, file, cmd, arg);
> + ret = __fb_ioctl(inode, file, cmd, arg);
> break;
>
> case FBIOGET_FSCREENINFO:
> @@ -1234,7 +1256,7 @@
> ret = fb->fb_compat_ioctl(info, cmd, arg);
> break;
> }
> - unlock_kernel();
> + mutex_unlock(&info->hwlock);
> return ret;
> }
> #endif
> @@ -1256,13 +1278,13 @@
> return -ENODEV;
> if (fb->fb_mmap) {
> int res;
> - lock_kernel();
> + mutex_lock(&info->hwlock);
> res = fb->fb_mmap(info, vma);
> - unlock_kernel();
> + mutex_unlock(&info->hwlock);
> return res;
> }
>
> - lock_kernel();
> + mutex_lock(&info->hwlock);
>
> /* frame buffer memory */
> start = info->fix.smem_start;
> @@ -1271,13 +1293,13 @@
> /* memory mapped io */
> off -= len;
> if (info->var.accel_flags) {
> - unlock_kernel();
> + mutex_unlock(&info->hwlock);
> return -EINVAL;
> }
> start = info->fix.mmio_start;
> len = PAGE_ALIGN((start & ~PAGE_MASK) + info->fix.mmio_len);
> }
> - unlock_kernel();
> + mutex_unlock(&info->hwlock);
> start &= PAGE_MASK;
> if ((vma->vm_end - vma->vm_start + off) > len)
> return -EINVAL;
> @@ -1323,25 +1345,25 @@
> {
> struct fb_info * const info = file->private_data;
>
> - lock_kernel();
> + mutex_lock(&info->hwlock);
> if (info->fbops->fb_release)
> info->fbops->fb_release(info,1);
> module_put(info->fbops->owner);
> - unlock_kernel();
> + mutex_unlock(&info->hwlock);
> return 0;
> }
>
> static const struct file_operations fb_fops = {
> - .owner = THIS_MODULE,
> - .read = fb_read,
> - .write = fb_write,
> - .ioctl = fb_ioctl,
> + .owner = THIS_MODULE,
> + .read = fb_read,
> + .write = fb_write,
> + .unlocked_ioctl = fb_unlocked_ioctl,
> #ifdef CONFIG_COMPAT
> - .compat_ioctl = fb_compat_ioctl,
> + .compat_ioctl = fb_compat_ioctl,
> #endif
> - .mmap = fb_mmap,
> - .open = fb_open,
> - .release = fb_release,
> + .mmap = fb_mmap,
> + .open = fb_open,
> + .release = fb_release,
> #ifdef HAVE_ARCH_FB_UNMAPPED_AREA
> .get_unmapped_area = get_fb_unmapped_area,
> #endif
> @@ -1377,6 +1399,7 @@
> break;
> fb_info->node = i;
>
> + mutex_init(&fb_info->hwlock);
> fb_info->dev = device_create(fb_class, fb_info->device,
> MKDEV(FB_MAJOR, i), "fb%d", i);
> if (IS_ERR(fb_info->dev)) {
> @@ -1413,6 +1436,7 @@
>
> event.info = fb_info;
> fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);
> +
> return 0;
> }
>
> @@ -1464,6 +1488,7 @@
> device_destroy(fb_class, MKDEV(FB_MAJOR, i));
> event.info = fb_info;
> fb_notifier_call_chain(FB_EVENT_FB_UNREGISTERED, &event);
> + mutex_destroy(&fb_info.hwlock);
> done:
> return ret;
> }
> Index: linux-2.6.23.1/include/linux/fb.h
> ===================================================================
> --- linux-2.6.23.1.orig/include/linux/fb.h 2008-04-16 18:52:32.000000000 -0300
> +++ linux-2.6.23.1/include/linux/fb.h 2008-04-16 18:53:22.000000000 -0300
> @@ -802,6 +802,7 @@
> struct list_head modelist; /* mode list */
> struct fb_videomode *mode; /* current mode */
>
> + struct mutex hwlock; /* mutex for protecting hw ops */
> #ifdef CONFIG_FB_BACKLIGHT
> /* assigned backlight device */
> /* set before framebuffer registration,
>
>
>
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