The patch titled
revert "fbmem: fix fb_info->lock and mm->mmap_sem circular locking dependency"
has been added to the -mm tree. Its filename is
revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency.patch
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------------------------------------------------------
Subject: revert "fbmem: fix fb_info->lock and mm->mmap_sem circular locking dependency"
From: Krzysztof Helt <krzysztof.h1@xxxxx>
A conversion of the BLK to the fb_info->lock mutex brought some circular
locking dependencies. Despite extensive effort to fix these problems
there are still some bugs left. The last effort unveiled a problem
described below. It is not fixable without rethinking how locking should
be done inside the fbdev layer.
Short summary of the lock dep is:
1. sys_munmap() obtains [mm->mmap_sem] and calls indirectly
:: fb_release() obtains [fb_info->lock]
2. fb_ioctl() obtains [fb_info->lock] and calls indirectly
:: fb_notifier_call_chain() obtains [fb_notifier_list->rwsem]
3. driver_probe_device() calls indirectly
:: register_framebuffer() calls indirectly
:: fb_notifier_call_chain() obtains [fb_notifier_list->rwsem] and calls indirectly
:: sysfs_create_dir() obtains [sysfs_mutex]
4. sysfs_readdir() obtains [sysfs_mutex] and calls indirectly
:: copy_to_user() obtains [mm->mmap_sem]
Revert the BKL to mutex conversion patch
(3e680aae4e53ab54cdbb0c29257dae0cbb158e1c) while keeping the patch which
made the fb_ioctl and the fb_compat_ioctl using a common function
(a684e7d33096892093456dd56a582cfc3bfad648).
This patch: revert
: commit 66c1ca019078220dc1bf968f2bb18421100ef147
: Author: Andrea Righi <righi.andrea@xxxxxxxxx>
: Date: Tue Mar 31 15:25:18 2009 -0700
:
: fbmem: fix fb_info->lock and mm->mmap_sem circular locking dependency
Signed-off-by: Krzysztof Helt <krzysztof.h1@xxxxx>
Cc: Andrea Righi <righi.andrea@xxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/video/backlight/backlight.c | 3 -
drivers/video/backlight/lcd.c | 3 -
drivers/video/console/fbcon.c | 71 +++-----------------------
drivers/video/fbmem.c | 11 +++-
4 files changed, 19 insertions(+), 69 deletions(-)
diff -puN drivers/video/backlight/backlight.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/backlight/backlight.c
--- a/drivers/video/backlight/backlight.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/drivers/video/backlight/backlight.c
@@ -35,8 +35,6 @@ static int fb_notifier_callback(struct n
return 0;
bd = container_of(self, struct backlight_device, fb_notif);
- if (!lock_fb_info(evdata->info))
- return -ENODEV;
mutex_lock(&bd->ops_lock);
if (bd->ops)
if (!bd->ops->check_fb ||
@@ -49,7 +47,6 @@ static int fb_notifier_callback(struct n
backlight_update_status(bd);
}
mutex_unlock(&bd->ops_lock);
- unlock_fb_info(evdata->info);
return 0;
}
diff -puN drivers/video/backlight/lcd.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/backlight/lcd.c
--- a/drivers/video/backlight/lcd.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/drivers/video/backlight/lcd.c
@@ -40,8 +40,6 @@ static int fb_notifier_callback(struct n
if (!ld->ops)
return 0;
- if (!lock_fb_info(evdata->info))
- return -ENODEV;
mutex_lock(&ld->ops_lock);
if (!ld->ops->check_fb || ld->ops->check_fb(ld, evdata->info)) {
if (event == FB_EVENT_BLANK) {
@@ -53,7 +51,6 @@ static int fb_notifier_callback(struct n
}
}
mutex_unlock(&ld->ops_lock);
- unlock_fb_info(evdata->info);
return 0;
}
diff -puN drivers/video/console/fbcon.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/console/fbcon.c
--- a/drivers/video/console/fbcon.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/drivers/video/console/fbcon.c
@@ -2954,11 +2954,8 @@ static int fbcon_fb_unbind(int idx)
static int fbcon_fb_unregistered(struct fb_info *info)
{
- int i, idx;
+ int i, idx = info->node;
- if (!lock_fb_info(info))
- return -ENODEV;
- idx = info->node;
for (i = first_fb_vc; i <= last_fb_vc; i++) {
if (con2fb_map[i] == idx)
con2fb_map[i] = -1;
@@ -2982,14 +2979,13 @@ static int fbcon_fb_unregistered(struct
}
}
- if (primary_device == idx)
- primary_device = -1;
-
- unlock_fb_info(info);
-
if (!num_registered_fb)
unregister_con_driver(&fb_con);
+
+ if (primary_device == idx)
+ primary_device = -1;
+
return 0;
}
@@ -3025,13 +3021,9 @@ static inline void fbcon_select_primary(
static int fbcon_fb_registered(struct fb_info *info)
{
- int ret = 0, i, idx;
+ int ret = 0, i, idx = info->node;
- if (!lock_fb_info(info))
- return -ENODEV;
- idx = info->node;
fbcon_select_primary(info);
- unlock_fb_info(info);
if (info_idx == -1) {
for (i = first_fb_vc; i <= last_fb_vc; i++) {
@@ -3140,7 +3132,7 @@ static int fbcon_event_notify(struct not
struct fb_videomode *mode;
struct fb_con2fbmap *con2fb;
struct fb_blit_caps *caps;
- int idx, ret = 0;
+ int ret = 0;
/*
* ignore all events except driver registration and deregistration
@@ -3152,54 +3144,23 @@ static int fbcon_event_notify(struct not
switch(action) {
case FB_EVENT_SUSPEND:
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
fbcon_suspended(info);
- unlock_fb_info(info);
break;
case FB_EVENT_RESUME:
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
fbcon_resumed(info);
- unlock_fb_info(info);
break;
case FB_EVENT_MODE_CHANGE:
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
fbcon_modechanged(info);
- unlock_fb_info(info);
break;
case FB_EVENT_MODE_CHANGE_ALL:
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
fbcon_set_all_vcs(info);
- unlock_fb_info(info);
break;
case FB_EVENT_MODE_DELETE:
mode = event->data;
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
ret = fbcon_mode_deleted(info, mode);
- unlock_fb_info(info);
break;
case FB_EVENT_FB_UNBIND:
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
- idx = info->node;
- unlock_fb_info(info);
- ret = fbcon_fb_unbind(idx);
+ ret = fbcon_fb_unbind(info->node);
break;
case FB_EVENT_FB_REGISTERED:
ret = fbcon_fb_registered(info);
@@ -3217,31 +3178,17 @@ static int fbcon_event_notify(struct not
con2fb->framebuffer = con2fb_map[con2fb->console - 1];
break;
case FB_EVENT_BLANK:
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
fbcon_fb_blanked(info, *(int *)event->data);
- unlock_fb_info(info);
break;
case FB_EVENT_NEW_MODELIST:
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
fbcon_new_modelist(info);
- unlock_fb_info(info);
break;
case FB_EVENT_GET_REQ:
caps = event->data;
- if (!lock_fb_info(info)) {
- ret = -ENODEV;
- goto done;
- }
fbcon_get_requirement(info, caps);
- unlock_fb_info(info);
break;
}
+
done:
return ret;
}
diff -puN drivers/video/fbmem.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency drivers/video/fbmem.c
--- a/drivers/video/fbmem.c~revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency
+++ a/drivers/video/fbmem.c
@@ -1086,8 +1086,13 @@ static long do_fb_ioctl(struct fb_info *
return -EINVAL;
con2fb.framebuffer = -1;
event.data = &con2fb;
+
+ if (!lock_fb_info(info))
+ return -ENODEV;
event.info = info;
fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP, &event);
+ unlock_fb_info(info);
+
ret = copy_to_user(argp, &con2fb, sizeof(con2fb)) ? -EFAULT : 0;
break;
case FBIOPUT_CON2FBMAP:
@@ -1104,8 +1109,12 @@ static long do_fb_ioctl(struct fb_info *
break;
}
event.data = &con2fb;
+ if (!lock_fb_info(info))
+ return -ENODEV;
event.info = info;
- ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP, &event);
+ ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP,
+ &event);
+ unlock_fb_info(info);
break;
case FBIOBLANK:
if (!lock_fb_info(info))
_
Patches currently in -mm which might be from krzysztof.h1@xxxxx are
viafb-make-it-work-on-x86_64.patch
linux-next.patch
revert-fbdev-fix-info-lock-deadlock-in-fbcon_event_notify.patch
revert-fbdev-uninline-lock_fb_info.patch
revert-fbmem-fix-fb_info-lock-and-mm-mmap_sem-circular-locking-dependency.patch
revert-fbmem-dont-call-copy_from-to_user-with-mutex-held.patch
chipsfb-remove-redundant-assignment.patch
igafb-use-framebuffer_alloc-to-allocate-fb_info-struct.patch
offb-use-framebuffer_alloc-to-allocate-fb_info-struct.patch
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