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[PATCH] Video: fb, add true ref_count atomicity
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Some of fb drivers uses atomic_t in bad manner, since there are still some
race-prone gaps.  Use mutexes to protect open/close code sections with
ref_count testing and finally use simple uint.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Denis Oliver Kropp <dok@directfb.org>
Cc: James Simmons <jsimmons@infradead.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Jiri Slaby authored and Linus Torvalds committed Feb 12, 2007
1 parent 52e7c92 commit c4f28e5
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Showing 7 changed files with 62 additions and 35 deletions.
3 changes: 2 additions & 1 deletion drivers/video/i810/i810.h
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Original file line number Diff line number Diff line change
Expand Up @@ -264,7 +264,8 @@ struct i810fb_par {
struct heap_data cursor_heap;
struct vgastate state;
struct i810fb_i2c_chan chan[3];
atomic_t use_count;
struct mutex open_lock;
unsigned int use_count;
u32 pseudo_palette[17];
unsigned long mmio_start_phys;
u8 __iomem *mmio_start_virtual;
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25 changes: 15 additions & 10 deletions drivers/video/i810/i810_main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1235,9 +1235,9 @@ static int i810fb_getcolreg(u8 regno, u8 *red, u8 *green, u8 *blue,
static int i810fb_open(struct fb_info *info, int user)
{
struct i810fb_par *par = info->par;
u32 count = atomic_read(&par->use_count);

if (count == 0) {

mutex_lock(&par->open_lock);
if (par->use_count == 0) {
memset(&par->state, 0, sizeof(struct vgastate));
par->state.flags = VGA_SAVE_CMAP;
par->state.vgabase = par->mmio_start_virtual;
Expand All @@ -1246,26 +1246,29 @@ static int i810fb_open(struct fb_info *info, int user)
i810_save_vga_state(par);
}

atomic_inc(&par->use_count);
par->use_count++;
mutex_unlock(&par->open_lock);

return 0;
}

static int i810fb_release(struct fb_info *info, int user)
{
struct i810fb_par *par = info->par;
u32 count;

count = atomic_read(&par->use_count);
if (count == 0)

mutex_lock(&par->open_lock);
if (par->use_count == 0) {
mutex_unlock(&par->open_lock);
return -EINVAL;
}

if (count == 1) {
if (par->use_count == 1) {
i810_restore_vga_state(par);
restore_vga(&par->state);
}

atomic_dec(&par->use_count);
par->use_count--;
mutex_unlock(&par->open_lock);

return 0;
}
Expand Down Expand Up @@ -1752,6 +1755,8 @@ static void __devinit i810_init_monspecs(struct fb_info *info)
static void __devinit i810_init_defaults(struct i810fb_par *par,
struct fb_info *info)
{
mutex_init(&par->open_lock);

if (voffset)
v_offset_default = voffset;
else if (par->aperture.size > 32 * 1024 * 1024)
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21 changes: 14 additions & 7 deletions drivers/video/neofb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -556,29 +556,35 @@ static int
neofb_open(struct fb_info *info, int user)
{
struct neofb_par *par = info->par;
int cnt = atomic_read(&par->ref_count);

if (!cnt) {
mutex_lock(&par->open_lock);
if (!par->ref_count) {
memset(&par->state, 0, sizeof(struct vgastate));
par->state.flags = VGA_SAVE_MODE | VGA_SAVE_FONTS;
save_vga(&par->state);
}
atomic_inc(&par->ref_count);
par->ref_count++;
mutex_unlock(&par->open_lock);

return 0;
}

static int
neofb_release(struct fb_info *info, int user)
{
struct neofb_par *par = info->par;
int cnt = atomic_read(&par->ref_count);

if (!cnt)
mutex_lock(&par->open_lock);
if (!par->ref_count) {
mutex_unlock(&par->open_lock);
return -EINVAL;
if (cnt == 1) {
}
if (par->ref_count == 1) {
restore_vga(&par->state);
}
atomic_dec(&par->ref_count);
par->ref_count--;
mutex_unlock(&par->open_lock);

return 0;
}

Expand Down Expand Up @@ -2047,6 +2053,7 @@ static struct fb_info *__devinit neo_alloc_fb_info(struct pci_dev *dev, const st

info->fix.accel = id->driver_data;

mutex_init(&par->open_lock);
par->pci_burst = !nopciburst;
par->lcd_stretch = !nostretch;
par->libretto = libretto;
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19 changes: 12 additions & 7 deletions drivers/video/riva/fbdev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1101,10 +1101,10 @@ static int riva_get_cmap_len(const struct fb_var_screeninfo *var)
static int rivafb_open(struct fb_info *info, int user)
{
struct riva_par *par = info->par;
int cnt = atomic_read(&par->ref_count);

NVTRACE_ENTER();
if (!cnt) {
mutex_lock(&par->open_lock);
if (!par->ref_count) {
#ifdef CONFIG_X86
memset(&par->state, 0, sizeof(struct vgastate));
par->state.flags = VGA_SAVE_MODE | VGA_SAVE_FONTS;
Expand All @@ -1119,20 +1119,23 @@ static int rivafb_open(struct fb_info *info, int user)

riva_save_state(par, &par->initial_state);
}
atomic_inc(&par->ref_count);
par->ref_count++;
mutex_unlock(&par->open_lock);
NVTRACE_LEAVE();
return 0;
}

static int rivafb_release(struct fb_info *info, int user)
{
struct riva_par *par = info->par;
int cnt = atomic_read(&par->ref_count);

NVTRACE_ENTER();
if (!cnt)
mutex_lock(&par->open_lock);
if (!par->ref_count) {
mutex_unlock(&par->open_lock);
return -EINVAL;
if (cnt == 1) {
}
if (par->ref_count == 1) {
par->riva.LockUnlock(&par->riva, 0);
par->riva.LoadStateExt(&par->riva, &par->initial_state.ext);
riva_load_state(par, &par->initial_state);
Expand All @@ -1141,7 +1144,8 @@ static int rivafb_release(struct fb_info *info, int user)
#endif
par->riva.LockUnlock(&par->riva, 1);
}
atomic_dec(&par->ref_count);
par->ref_count--;
mutex_unlock(&par->open_lock);
NVTRACE_LEAVE();
return 0;
}
Expand Down Expand Up @@ -1999,6 +2003,7 @@ static int __devinit rivafb_probe(struct pci_dev *pd,
goto err_disable_device;
}

mutex_init(&default_par->open_lock);
default_par->riva.Architecture = riva_get_arch(pd);

default_par->Chipset = (pd->vendor << 16) | pd->device;
Expand Down
3 changes: 2 additions & 1 deletion drivers/video/riva/rivafb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,8 @@ struct riva_par {
#ifdef CONFIG_X86
struct vgastate state;
#endif
atomic_t ref_count;
struct mutex open_lock;
unsigned int ref_count;
unsigned char *EDID;
unsigned int Chipset;
int forceCRTC;
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23 changes: 15 additions & 8 deletions drivers/video/vga16fb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,8 @@ struct vga16fb_par {
unsigned char ClockingMode; /* Seq-Controller:01h */
} vga_state;
struct vgastate state;
atomic_t ref_count;
struct mutex open_lock;
unsigned int ref_count;
int palette_blanked, vesa_blanked, mode, isVGA;
u8 misc, pel_msk, vss, clkdiv;
u8 crtc[VGA_CRT_C];
Expand Down Expand Up @@ -300,28 +301,33 @@ static void vga16fb_clock_chip(struct vga16fb_par *par,
static int vga16fb_open(struct fb_info *info, int user)
{
struct vga16fb_par *par = info->par;
int cnt = atomic_read(&par->ref_count);

if (!cnt) {
mutex_lock(&par->open_lock);
if (!par->ref_count) {
memset(&par->state, 0, sizeof(struct vgastate));
par->state.flags = VGA_SAVE_FONTS | VGA_SAVE_MODE |
VGA_SAVE_CMAP;
save_vga(&par->state);
}
atomic_inc(&par->ref_count);
par->ref_count++;
mutex_unlock(&par->open_lock);

return 0;
}

static int vga16fb_release(struct fb_info *info, int user)
{
struct vga16fb_par *par = info->par;
int cnt = atomic_read(&par->ref_count);

if (!cnt)
mutex_lock(&par->open_lock);
if (!par->ref_count) {
mutex_unlock(&par->open_lock);
return -EINVAL;
if (cnt == 1)
}
if (par->ref_count == 1)
restore_vga(&par->state);
atomic_dec(&par->ref_count);
par->ref_count--;
mutex_unlock(&par->open_lock);

return 0;
}
Expand Down Expand Up @@ -1357,6 +1363,7 @@ static int __init vga16fb_probe(struct platform_device *dev)
printk(KERN_INFO "vga16fb: mapped to 0x%p\n", info->screen_base);
par = info->par;

mutex_init(&par->open_lock);
par->isVGA = ORIG_VIDEO_ISVGA;
par->palette_blanked = 0;
par->vesa_blanked = 0;
Expand Down
3 changes: 2 additions & 1 deletion include/video/neomagic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -140,7 +140,8 @@ typedef volatile struct {

struct neofb_par {
struct vgastate state;
atomic_t ref_count;
struct mutex open_lock;
unsigned int ref_count;

unsigned char MiscOutReg; /* Misc */
unsigned char CRTC[25]; /* Crtc Controller */
Expand Down

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