Re: [Linux-fbdev-devel] [2.6.29-rc2] fb_mmap: circular locking dependency on hibernation

From: Andrey Borzenkov
Date: Wed Feb 04 2009 - 03:20:31 EST

On 3 of February 2009 13:09:38 Andrea Righi wrote:
> On 2009-02-02 18:36, Andrey Borzenkov wrote:
> > I hope you do not think I'm doing this on purpose? :)
>
> LOL!
>
> Don't worry, we'll be able to fix it before linux 3.0.0 (maybe).
>

My be earlier.

Tested-by: Andrey Borzenkov <arvidjaar@xxxxxxx>

This bug causes text mode corruption sometimes so patch should
definitely go into 2.6.29.

> > [ 241.668005]
> > ======================================================= [
> > 241.668044] [ INFO: possible circular locking dependency detected ]
> > [ 241.668068] 2.6.29-rc3-1avb #17
> > [ 241.668080]
> > ------------------------------------------------------- [
> > 241.668100] s2disk/4219 is trying to acquire lock:
> > [ 241.668118] (&fb_info->lock){--..}, at: [<c02235e7>]
> > fb_mmap+0x97/0x170
> > [ 241.668188]
> > [ 241.668190] but task is already holding lock:
> > [ 241.668207] (&mm->mmap_sem){----}, at: [<c010639e>]
> > sys_mmap2+0x8e/0xc0
> > [ 241.668256]
> > [ 241.668258] which lock already depends on the new lock.
> > [ 241.668262]
> > [ 241.668282]
> > [ 241.668284] the existing dependency chain (in reverse order) is:
> > [ 241.668305]
> > [ 241.668307] -> #2 (&mm->mmap_sem){----}:
> > [ 241.668331] [<c014520f>] __lock_acquire+0x129f/0x1930
> > [ 241.668362] [<c01458fc>] lock_acquire+0x5c/0x80
> > [ 241.668382] [<c0182117>] might_fault+0x77/0xa0
> > [ 241.668413] [<c0209916>] copy_to_user+0x36/0x120
> > [ 241.668439] [<c01a60f7>] filldir+0x97/0xe0
> > [ 241.668482] [<c01de339>] sysfs_readdir+0x129/0x220
> > [ 241.668508] [<c01a62a6>] vfs_readdir+0x86/0xa0
> > [ 241.668529] [<c01a63e8>] sys_getdents+0x68/0xc0
> > [ 241.668549] [<c010344a>] syscall_call+0x7/0xb
> > [ 241.668570] [<ffffffff>] 0xffffffff
> > [ 241.668650]
> > [ 241.668653] -> #1 (sysfs_mutex){--..}:
> > [ 241.668676] [<c014520f>] __lock_acquire+0x129f/0x1930
> > [ 241.668698] [<c01458fc>] lock_acquire+0x5c/0x80
> > [ 241.668718] [<c030820a>] mutex_lock_nested+0xba/0x2f0
> > [ 241.668749] [<c01de6cc>] sysfs_addrm_start+0x2c/0xc0
> > [ 241.668771] [<c01dec80>] create_dir+0x40/0x90
> > [ 241.668792] [<c01decfb>] sysfs_create_dir+0x2b/0x50
> > [ 241.668812] [<c02036bc>] kobject_add_internal+0xbc/0x1b0
> > [ 241.668853] [<c0203881>] kobject_add_varg+0x31/0x50
> > [ 241.668874] [<c02038fc>] kobject_add+0x2c/0x60
> > [ 241.668895] [<c0273718>] device_add+0xa8/0x550
> > [ 241.668938] [<c0273bd2>] device_register+0x12/0x20
> > [ 241.668960] [<c0273c8b>] device_create_vargs+0xab/0xc0
> > [ 241.668982] [<c0273cc8>] device_create+0x28/0x30
> > [ 241.669003] [<c026cf3d>] register_con_driver+0xed/0x130
> > [ 241.669027] [<c026e45b>] take_over_console+0x1b/0x50
> > [ 241.669049] [<c02304dd>] fbcon_takeover+0x5d/0xb0
> > [ 241.669081] [<c0231457>] fbcon_event_notify+0xb27/0xc20
> > [ 241.669104] [<c030c683>] notifier_call_chain+0x53/0xa0
> > [ 241.669138] [<c0138ab4>]
> > __blocking_notifier_call_chain+0x44/0x60
> > [ 241.669218] [<c0138aea>]
> > blocking_notifier_call_chain+0x1a/0x20
> > [ 241.669246] [<c0222f81>] fb_notifier_call_chain+0x11/0x20
> > [ 241.669276] [<c0223f08>] register_framebuffer+0x168/0x220
> > [ 241.669305] [<c0414ba2>] vesafb_probe+0x542/0x783
> > [ 241.669347] [<c027687f>] platform_drv_probe+0xf/0x20
> > [ 241.669378] [<c0275a97>] driver_probe_device+0x87/0x1b0
> > [ 241.669404] [<c0275c58>] __device_attach+0x8/0x10
> > [ 241.669429] [<c02750db>] bus_for_each_drv+0x5b/0x80
> > [ 241.669460] [<c0275d06>] device_attach+0x76/0x80
> > [ 241.669484] [<c0274ef7>] bus_attach_device+0x47/0x70
> > [ 241.669511] [<c0273993>] device_add+0x323/0x550
> > [ 241.669536] [<c0277255>] platform_device_add+0x175/0x1c0
> > [ 241.669567] [<c0414e7d>] vesafb_init+0x9a/0x1ec
> > [ 241.669592] [<c010111a>] do_one_initcall+0x2a/0x160
> > [ 241.669619] [<c04004d5>] kernel_init+0x83/0xd5
> > [ 241.669661] [<c0103a77>] kernel_thread_helper+0x7/0x10
> > [ 241.669688] [<ffffffff>] 0xffffffff
> > [ 241.669737]
> > [ 241.669739] -> #0 (&fb_info->lock){--..}:
> > [ 241.669770] [<c014537c>] __lock_acquire+0x140c/0x1930
> > [ 241.669797] [<c01458fc>] lock_acquire+0x5c/0x80
> > [ 241.669821] [<c030820a>] mutex_lock_nested+0xba/0x2f0
> > [ 241.669847] [<c02235e7>] fb_mmap+0x97/0x170
> > [ 241.669872] [<c0188c76>] mmap_region+0x1d6/0x530
> > [ 241.669908] [<c01891a3>] do_mmap_pgoff+0x1d3/0x2f0
> > [ 241.669934] [<c01063bd>] sys_mmap2+0xad/0xc0
> > [ 241.669959] [<c0103371>] sysenter_do_call+0x12/0x31
> > [ 241.669984] [<ffffffff>] 0xffffffff
> > [ 241.670009]
> > [ 241.670012] other info that might help us debug this:
> > [ 241.670015]
> > [ 241.670049] 1 lock held by s2disk/4219:
> > [ 241.670065] #0: (&mm->mmap_sem){----}, at: [<c010639e>]
> > sys_mmap2+0x8e/0xc0
> > [ 241.670092]
> > [ 241.670092] stack backtrace:
> > [ 241.670092] Pid: 4219, comm: s2disk Not tainted 2.6.29-rc3-1avb
> > #17 [ 241.670092] Call Trace:
> > [ 241.670092] [<c0306e38>] ? printk+0x18/0x20
> > [ 241.670092] [<c0143b1f>] print_circular_bug_tail+0xcf/0xe0
> > [ 241.670092] [<c014537c>] __lock_acquire+0x140c/0x1930
> > [ 241.670092] [<c01487f0>] ? futex_wait+0x170/0x450
> > [ 241.670092] [<c011826c>] ? try_to_wake_up+0x10c/0x120
> > [ 241.670092] [<c0309d15>] ? _spin_unlock_irqrestore+0x35/0x60
> > [ 241.670092] [<c0141105>] ? lock_release_holdtime+0x35/0x210
> > [ 241.670092] [<c01458fc>] lock_acquire+0x5c/0x80
> > [ 241.670092] [<c02235e7>] ? fb_mmap+0x97/0x170
> > [ 241.670092] [<c030820a>] mutex_lock_nested+0xba/0x2f0
> > [ 241.670092] [<c02235e7>] ? fb_mmap+0x97/0x170
> > [ 241.670092] [<c02235e7>] ? fb_mmap+0x97/0x170
> > [ 241.670092] [<c019542d>] ? kmem_cache_alloc+0xad/0x100
> > [ 241.670092] [<c02235e7>] fb_mmap+0x97/0x170
> > [ 241.670092] [<c0188c76>] mmap_region+0x1d6/0x530
> > [ 241.670092] [<c0186cfd>] ?
> > arch_get_unmapped_area_topdown+0x8d/0x170 [ 241.670092]
> > [<c01891a3>] do_mmap_pgoff+0x1d3/0x2f0
> > [ 241.670092] [<c01063bd>] sys_mmap2+0xad/0xc0
> > [ 241.670092] [<c0103371>] sysenter_do_call+0x12/0x31
> > [ 244.217754] Syncing filesystems ... done.
> > [ 244.228175] Freezing user space processes ... (elapsed 0.00
> > seconds) done.
>
> OK, another patch. This one is a cumulative patch against the latest
> Linus' git.
>
> Thanks again!
> -Andrea
>
> ---
> fbmem: fix circular locking dependency between fb_info->lock and
> mm->mmap_sem
>
> Avoid calling copy_from/to_user() with fb_info->lock mutex held in
> the framebuffer's ioctl().
>
> fb_mmap() is called under mm->mmap_sem (A) held, that also acquires
> fb_info->lock (B); fb_ioctl() takes fb_info->lock (B) and does
> copy_from/to_user() that might acquire mm->mmap_sem (A), causing a
> deadlock.
>
> Also fix other potential circular locking dependencies (always
> between fb_info->lock and mm->mmap_sem) in fbcon that occur calling
> the blocking fb_notifier_call_chain() with fb_info->lock held.
>
> NOTE: it doesn't push down the fb_info->lock in each own driver's
> specific fb_ioctl() implementation, so there are still some potential
> deadlocks elsewhere.
>
> CC: Andrey Borzenkov <arvidjaar@xxxxxxx>
> Signed-off-by: Andrea Righi <righi.andrea@xxxxxxxxx>
> ---
> drivers/video/backlight/backlight.c | 3 +
> drivers/video/backlight/lcd.c | 3 +
> drivers/video/console/fbcon.c | 73 +++++++++++++++++---
> drivers/video/fbcmap.c | 20 ++++--
> drivers/video/fbmem.c | 128
> +++++++++++++++++------------------ include/linux/fb.h
> | 15 ++++
> 6 files changed, 160 insertions(+), 82 deletions(-)
>
> diff --git a/drivers/video/backlight/backlight.c
> b/drivers/video/backlight/backlight.c index 157057c..dd37cbc 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -35,6 +35,8 @@ static int fb_notifier_callback(struct
> notifier_block *self, 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 ||
> @@ -47,6 +49,7 @@ static int fb_notifier_callback(struct
> notifier_block *self, backlight_update_status(bd);
> }
> mutex_unlock(&bd->ops_lock);
> + unlock_fb_info(evdata->info);
> return 0;
> }
>
> diff --git a/drivers/video/backlight/lcd.c
> b/drivers/video/backlight/lcd.c index b644947..0bb13df 100644
> --- a/drivers/video/backlight/lcd.c
> +++ b/drivers/video/backlight/lcd.c
> @@ -40,6 +40,8 @@ static int fb_notifier_callback(struct
> notifier_block *self, 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) {
> @@ -51,6 +53,7 @@ static int fb_notifier_callback(struct
> notifier_block *self, }
> }
> mutex_unlock(&ld->ops_lock);
> + unlock_fb_info(evdata->info);
> return 0;
> }
>
> diff --git a/drivers/video/console/fbcon.c
> b/drivers/video/console/fbcon.c index 1657b96..2cd500a 100644
> --- a/drivers/video/console/fbcon.c
> +++ b/drivers/video/console/fbcon.c
> @@ -2954,8 +2954,11 @@ static int fbcon_fb_unbind(int idx)
>
> static int fbcon_fb_unregistered(struct fb_info *info)
> {
> - int i, idx = info->node;
> + int i, idx;
>
> + 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;
> @@ -2979,13 +2982,14 @@ static int fbcon_fb_unregistered(struct
> fb_info *info) }
> }
>
> - if (!num_registered_fb)
> - unregister_con_driver(&fb_con);
> -
> -
> if (primary_device == idx)
> primary_device = -1;
>
> + unlock_fb_info(info);
> +
> + if (!num_registered_fb)
> + unregister_con_driver(&fb_con);
> +
> return 0;
> }
>
> @@ -3021,9 +3025,13 @@ static inline void fbcon_select_primary(struct
> fb_info *info)
>
> static int fbcon_fb_registered(struct fb_info *info)
> {
> - int ret = 0, i, idx = info->node;
> + int ret = 0, i, idx;
>
> + 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++) {
> @@ -3124,7 +3132,7 @@ static void fbcon_get_requirement(struct
> fb_info *info, }
> }
>
> -static int fbcon_event_notify(struct notifier_block *self,
> +static int fbcon_event_notify(struct notifier_block *self,
> unsigned long action, void *data)
> {
> struct fb_event *event = data;
> @@ -3132,7 +3140,7 @@ static int fbcon_event_notify(struct
> notifier_block *self, struct fb_videomode *mode;
> struct fb_con2fbmap *con2fb;
> struct fb_blit_caps *caps;
> - int ret = 0;
> + int idx, ret = 0;
>
> /*
> * ignore all events except driver registration and deregistration
> @@ -3144,23 +3152,54 @@ static int fbcon_event_notify(struct
> notifier_block *self,
>
> 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:
> - ret = fbcon_fb_unbind(info->node);
> + if (!lock_fb_info(info)) {
> + ret = -ENODEV;
> + goto done;
> + }
> + idx = info->node;
> + unlock_fb_info(info);
> + ret = fbcon_fb_unbind(idx);
> break;
> case FB_EVENT_FB_REGISTERED:
> ret = fbcon_fb_registered(info);
> @@ -3178,17 +3217,31 @@ static int fbcon_event_notify(struct
> notifier_block *self, 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 --git a/drivers/video/fbcmap.c b/drivers/video/fbcmap.c
> index 91b78e6..f53b9f1 100644
> --- a/drivers/video/fbcmap.c
> +++ b/drivers/video/fbcmap.c
> @@ -250,10 +250,6 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap,
> struct fb_info *info) int rc, size = cmap->len * sizeof(u16);
> struct fb_cmap umap;
>
> - if (cmap->start < 0 || (!info->fbops->fb_setcolreg &&
> - !info->fbops->fb_setcmap))
> - return -EINVAL;
> -
> memset(&umap, 0, sizeof(struct fb_cmap));
> rc = fb_alloc_cmap(&umap, cmap->len, cmap->transp != NULL);
> if (rc)
> @@ -262,11 +258,23 @@ int fb_set_user_cmap(struct fb_cmap_user *cmap,
> struct fb_info *info) copy_from_user(umap.green, cmap->green, size)
> ||
> copy_from_user(umap.blue, cmap->blue, size) ||
> (cmap->transp && copy_from_user(umap.transp, cmap->transp,
> size))) { - fb_dealloc_cmap(&umap);
> - return -EFAULT;
> + rc = -EFAULT;
> + goto out;
> }
> umap.start = cmap->start;
> + if (!lock_fb_info(info)) {
> + rc = -ENODEV;
> + goto out;
> + }
> + if (cmap->start < 0 || (!info->fbops->fb_setcolreg &&
> + !info->fbops->fb_setcmap)) {
> + rc = -EINVAL;
> + goto out1;
> + }
> rc = fb_set_cmap(&umap, info);
> +out1:
> + unlock_fb_info(info);
> +out:
> fb_dealloc_cmap(&umap);
> return rc;
> }
> diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
> index 756efeb..5cdee72 100644
> --- a/drivers/video/fbmem.c
> +++ b/drivers/video/fbmem.c
> @@ -1013,132 +1013,132 @@ static long do_fb_ioctl(struct fb_info
> *info, unsigned int cmd, struct fb_var_screeninfo var;
> struct fb_fix_screeninfo fix;
> struct fb_con2fbmap con2fb;
> + struct fb_cmap cmap_from;
> struct fb_cmap_user cmap;
> struct fb_event event;
> void __user *argp = (void __user *)arg;
> long ret = 0;
>
> - fb = info->fbops;
> - if (!fb)
> - return -ENODEV;
> -
> switch (cmd) {
> case FBIOGET_VSCREENINFO:
> - ret = copy_to_user(argp, &info->var,
> - sizeof(var)) ? -EFAULT : 0;
> + if (!lock_fb_info(info))
> + return -ENODEV;
> + var = info->var;
> + unlock_fb_info(info);
> +
> + ret = copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0;
> break;
> case FBIOPUT_VSCREENINFO:
> - if (copy_from_user(&var, argp, sizeof(var))) {
> - ret = -EFAULT;
> - break;
> - }
> + if (copy_from_user(&var, argp, sizeof(var)))
> + return -EFAULT;
> + if (!lock_fb_info(info))
> + return -ENODEV;
> acquire_console_sem();
> info->flags |= FBINFO_MISC_USEREVENT;
> ret = fb_set_var(info, &var);
> info->flags &= ~FBINFO_MISC_USEREVENT;
> release_console_sem();
> - if (ret == 0 && copy_to_user(argp, &var, sizeof(var)))
> + unlock_fb_info(info);
> + if (!ret && copy_to_user(argp, &var, sizeof(var)))
> ret = -EFAULT;
> break;
> case FBIOGET_FSCREENINFO:
> - ret = copy_to_user(argp, &info->fix,
> - sizeof(fix)) ? -EFAULT : 0;
> + if (!lock_fb_info(info))
> + return -ENODEV;
> + fix = info->fix;
> + unlock_fb_info(info);
> +
> + ret = copy_to_user(argp, &fix, sizeof(fix)) ? -EFAULT : 0;
> break;
> case FBIOPUTCMAP:
> if (copy_from_user(&cmap, argp, sizeof(cmap)))
> - ret = -EFAULT;
> - else
> - ret = fb_set_user_cmap(&cmap, info);
> + return -EFAULT;
> + ret = fb_set_user_cmap(&cmap, info);
> break;
> case FBIOGETCMAP:
> if (copy_from_user(&cmap, argp, sizeof(cmap)))
> - ret = -EFAULT;
> - else
> - ret = fb_cmap_to_user(&info->cmap, &cmap);
> + return -EFAULT;
> + if (!lock_fb_info(info))
> + return -ENODEV;
> + cmap_from = info->cmap;
> + unlock_fb_info(info);
> + ret = fb_cmap_to_user(&cmap_from, &cmap);
> break;
> case FBIOPAN_DISPLAY:
> - if (copy_from_user(&var, argp, sizeof(var))) {
> - ret = -EFAULT;
> - break;
> - }
> + if (copy_from_user(&var, argp, sizeof(var)))
> + return -EFAULT;
> + if (!lock_fb_info(info))
> + return -ENODEV;
> acquire_console_sem();
> ret = fb_pan_display(info, &var);
> release_console_sem();
> + unlock_fb_info(info);
> if (ret == 0 && copy_to_user(argp, &var, sizeof(var)))
> - ret = -EFAULT;
> + return -EFAULT;
> break;
> case FBIO_CURSOR:
> ret = -EINVAL;
> break;
> case FBIOGET_CON2FBMAP:
> if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
> - ret = -EFAULT;
> - else if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
> - ret = -EINVAL;
> - else {
> - con2fb.framebuffer = -1;
> - event.info = info;
> - event.data = &con2fb;
> - fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP,
> - &event);
> - ret = copy_to_user(argp, &con2fb,
> - sizeof(con2fb)) ? -EFAULT : 0;
> - }
> + return -EFAULT;
> + if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
> + return -EINVAL;
> + con2fb.framebuffer = -1;
> + event.data = &con2fb;
> + event.info = info;
> + fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP, &event);
> +
> + ret = copy_to_user(argp, &con2fb, sizeof(con2fb)) ? -EFAULT : 0;
> break;
> case FBIOPUT_CON2FBMAP:
> - if (copy_from_user(&con2fb, argp, sizeof(con2fb))) {
> - ret = -EFAULT;
> - break;
> - }
> - if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES) {
> - ret = -EINVAL;
> - break;
> - }
> - if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX) {
> - ret = -EINVAL;
> - break;
> - }
> + if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
> + return -EFAULT;
> + if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
> + return -EINVAL;
> + if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX)
> + return -EINVAL;
> if (!registered_fb[con2fb.framebuffer])
> request_module("fb%d", con2fb.framebuffer);
> if (!registered_fb[con2fb.framebuffer]) {
> ret = -EINVAL;
> break;
> }
> - event.info = info;
> event.data = &con2fb;
> + event.info = info;
> ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP,
> &event);
> break;
> case FBIOBLANK:
> + if (!lock_fb_info(info))
> + return -ENODEV;
> acquire_console_sem();
> info->flags |= FBINFO_MISC_USEREVENT;
> ret = fb_blank(info, arg);
> info->flags &= ~FBINFO_MISC_USEREVENT;
> release_console_sem();
> - break;;
> + unlock_fb_info(info);
> + break;
> default:
> - if (fb->fb_ioctl == NULL)
> - ret = -ENOTTY;
> - else
> + if (!lock_fb_info(info))
> + return -ENODEV;
> + fb = info->fbops;
> + if (fb->fb_ioctl)
> ret = fb->fb_ioctl(info, cmd, arg);
> + else
> + ret = -ENOTTY;
> + unlock_fb_info(info);
> }
> return ret;
> }
>
> static long fb_ioctl(struct file *file, unsigned int cmd, unsigned
> long arg) -__acquires(&info->lock)
> -__releases(&info->lock)
> {
> struct inode *inode = file->f_path.dentry->d_inode;
> int fbidx = iminor(inode);
> - struct fb_info *info;
> - long ret;
> + struct fb_info *info = registered_fb[fbidx];
>
> - info = registered_fb[fbidx];
> - mutex_lock(&info->lock);
> - ret = do_fb_ioctl(info, cmd, arg);
> - mutex_unlock(&info->lock);
> - return ret;
> + return do_fb_ioctl(info, cmd, arg);
> }
>
> #ifdef CONFIG_COMPAT
> @@ -1257,8 +1257,6 @@ static int fb_get_fscreeninfo(struct fb_info
> *info, unsigned int cmd,
>
> static long fb_compat_ioctl(struct file *file, unsigned int cmd,
> unsigned long arg)
> -__acquires(&info->lock)
> -__releases(&info->lock)
> {
> struct inode *inode = file->f_path.dentry->d_inode;
> int fbidx = iminor(inode);
> @@ -1266,7 +1264,6 @@ __releases(&info->lock)
> struct fb_ops *fb = info->fbops;
> long ret = -ENOIOCTLCMD;
>
> - mutex_lock(&info->lock);
> switch(cmd) {
> case FBIOGET_VSCREENINFO:
> case FBIOPUT_VSCREENINFO:
> @@ -1292,7 +1289,6 @@ __releases(&info->lock)
> ret = fb->fb_compat_ioctl(info, cmd, arg);
> break;
> }
> - mutex_unlock(&info->lock);
> return ret;
> }
> #endif
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index 818fe21..31527e1 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -960,6 +960,21 @@ extern struct fb_info *registered_fb[FB_MAX];
> extern int num_registered_fb;
> extern struct class *fb_class;
>
> +static inline int lock_fb_info(struct fb_info *info)
> +{
> + mutex_lock(&info->lock);
> + if (!info->fbops) {
> + mutex_unlock(&info->lock);
> + return 0;
> + }
> + return 1;
> +}
> +
> +static inline void unlock_fb_info(struct fb_info *info)
> +{
> + mutex_unlock(&info->lock);
> +}
> +
> static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
> u8 *src, u32 s_pitch, u32 height)
> {

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