[PATCH] Video: fb, add true ref_count atomicity
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>
diff --git a/drivers/video/riva/fbdev.c b/drivers/video/riva/fbdev.c
index 1a13966..7c19b5c2a 100644
--- a/drivers/video/riva/fbdev.c
+++ b/drivers/video/riva/fbdev.c
@@ -1101,10 +1101,10 @@
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;
@@ -1119,7 +1119,8 @@
riva_save_state(par, &par->initial_state);
}
- atomic_inc(&par->ref_count);
+ par->ref_count++;
+ mutex_unlock(&par->open_lock);
NVTRACE_LEAVE();
return 0;
}
@@ -1127,12 +1128,14 @@
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);
@@ -1141,7 +1144,8 @@
#endif
par->riva.LockUnlock(&par->riva, 1);
}
- atomic_dec(&par->ref_count);
+ par->ref_count--;
+ mutex_unlock(&par->open_lock);
NVTRACE_LEAVE();
return 0;
}
@@ -1999,6 +2003,7 @@
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;
diff --git a/drivers/video/riva/rivafb.h b/drivers/video/riva/rivafb.h
index 7fa13fc..48ead6d 100644
--- a/drivers/video/riva/rivafb.h
+++ b/drivers/video/riva/rivafb.h
@@ -53,7 +53,8 @@
#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;
