snapshot: Use pm_mutex for mutual exclusion
We can avoid taking the BKL in snapshot_ioctl() if pm_mutex is used to prevent the ioctls from being executed concurrently. In addition, although it is only possible to open /dev/snapshot once, the task which has done that may spawn a child that will inherit the open descriptor, so in theory they can call snapshot_write(), snapshot_read() and snapshot_release() concurrently. pm_mutex can also be used for mutual exclusion in such cases. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Signed-off-by: Andi Kleen <ak@linux.intel.com> Acked-by: Pavel Machek <pavel@suse.cz> Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
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52d11025db
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25f2f3daad
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@ -70,16 +70,22 @@ static int snapshot_open(struct inode *inode, struct file *filp)
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struct snapshot_data *data;
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struct snapshot_data *data;
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int error;
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int error;
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if (!atomic_add_unless(&snapshot_device_available, -1, 0))
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mutex_lock(&pm_mutex);
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return -EBUSY;
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if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
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error = -EBUSY;
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goto Unlock;
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}
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if ((filp->f_flags & O_ACCMODE) == O_RDWR) {
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if ((filp->f_flags & O_ACCMODE) == O_RDWR) {
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atomic_inc(&snapshot_device_available);
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atomic_inc(&snapshot_device_available);
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return -ENOSYS;
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error = -ENOSYS;
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goto Unlock;
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}
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}
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if(create_basic_memory_bitmaps()) {
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if(create_basic_memory_bitmaps()) {
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atomic_inc(&snapshot_device_available);
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atomic_inc(&snapshot_device_available);
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return -ENOMEM;
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error = -ENOMEM;
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goto Unlock;
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}
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}
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nonseekable_open(inode, filp);
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nonseekable_open(inode, filp);
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data = &snapshot_state;
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data = &snapshot_state;
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@ -99,33 +105,36 @@ static int snapshot_open(struct inode *inode, struct file *filp)
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if (error)
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if (error)
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pm_notifier_call_chain(PM_POST_HIBERNATION);
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pm_notifier_call_chain(PM_POST_HIBERNATION);
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}
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}
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if (error) {
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if (error)
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atomic_inc(&snapshot_device_available);
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atomic_inc(&snapshot_device_available);
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return error;
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}
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data->frozen = 0;
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data->frozen = 0;
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data->ready = 0;
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data->ready = 0;
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data->platform_support = 0;
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data->platform_support = 0;
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return 0;
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Unlock:
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mutex_unlock(&pm_mutex);
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return error;
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}
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}
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static int snapshot_release(struct inode *inode, struct file *filp)
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static int snapshot_release(struct inode *inode, struct file *filp)
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{
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{
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struct snapshot_data *data;
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struct snapshot_data *data;
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mutex_lock(&pm_mutex);
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swsusp_free();
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swsusp_free();
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free_basic_memory_bitmaps();
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free_basic_memory_bitmaps();
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data = filp->private_data;
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data = filp->private_data;
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free_all_swap_pages(data->swap);
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free_all_swap_pages(data->swap);
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if (data->frozen) {
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if (data->frozen)
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mutex_lock(&pm_mutex);
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thaw_processes();
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thaw_processes();
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mutex_unlock(&pm_mutex);
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}
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pm_notifier_call_chain(data->mode == O_WRONLY ?
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pm_notifier_call_chain(data->mode == O_WRONLY ?
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PM_POST_HIBERNATION : PM_POST_RESTORE);
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PM_POST_HIBERNATION : PM_POST_RESTORE);
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atomic_inc(&snapshot_device_available);
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atomic_inc(&snapshot_device_available);
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mutex_unlock(&pm_mutex);
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return 0;
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return 0;
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}
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}
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@ -135,9 +144,13 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf,
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struct snapshot_data *data;
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struct snapshot_data *data;
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ssize_t res;
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ssize_t res;
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mutex_lock(&pm_mutex);
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data = filp->private_data;
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data = filp->private_data;
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if (!data->ready)
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if (!data->ready) {
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return -ENODATA;
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res = -ENODATA;
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goto Unlock;
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}
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res = snapshot_read_next(&data->handle, count);
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res = snapshot_read_next(&data->handle, count);
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if (res > 0) {
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if (res > 0) {
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if (copy_to_user(buf, data_of(data->handle), res))
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if (copy_to_user(buf, data_of(data->handle), res))
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@ -145,6 +158,10 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf,
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else
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else
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*offp = data->handle.offset;
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*offp = data->handle.offset;
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}
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}
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Unlock:
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mutex_unlock(&pm_mutex);
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return res;
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return res;
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}
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}
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@ -154,6 +171,8 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf,
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struct snapshot_data *data;
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struct snapshot_data *data;
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ssize_t res;
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ssize_t res;
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mutex_lock(&pm_mutex);
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data = filp->private_data;
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data = filp->private_data;
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res = snapshot_write_next(&data->handle, count);
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res = snapshot_write_next(&data->handle, count);
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if (res > 0) {
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if (res > 0) {
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@ -162,6 +181,9 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf,
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else
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else
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*offp = data->handle.offset;
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*offp = data->handle.offset;
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}
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}
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mutex_unlock(&pm_mutex);
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return res;
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return res;
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}
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}
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@ -180,16 +202,16 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
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if (!capable(CAP_SYS_ADMIN))
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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return -EPERM;
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data = filp->private_data;
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if (!mutex_trylock(&pm_mutex))
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return -EBUSY;
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lock_kernel();
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data = filp->private_data;
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switch (cmd) {
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switch (cmd) {
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case SNAPSHOT_FREEZE:
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case SNAPSHOT_FREEZE:
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if (data->frozen)
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if (data->frozen)
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break;
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break;
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mutex_lock(&pm_mutex);
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printk("Syncing filesystems ... ");
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printk("Syncing filesystems ... ");
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sys_sync();
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sys_sync();
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printk("done.\n");
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printk("done.\n");
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@ -197,7 +219,6 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
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error = freeze_processes();
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error = freeze_processes();
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if (error)
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if (error)
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thaw_processes();
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thaw_processes();
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mutex_unlock(&pm_mutex);
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if (!error)
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if (!error)
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data->frozen = 1;
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data->frozen = 1;
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break;
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break;
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@ -205,9 +226,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
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case SNAPSHOT_UNFREEZE:
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case SNAPSHOT_UNFREEZE:
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if (!data->frozen || data->ready)
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if (!data->frozen || data->ready)
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break;
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break;
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mutex_lock(&pm_mutex);
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thaw_processes();
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thaw_processes();
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mutex_unlock(&pm_mutex);
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data->frozen = 0;
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data->frozen = 0;
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break;
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break;
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@ -310,16 +329,11 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
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error = -EPERM;
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error = -EPERM;
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break;
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break;
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}
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}
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if (!mutex_trylock(&pm_mutex)) {
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error = -EBUSY;
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break;
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}
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/*
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/*
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* Tasks are frozen and the notifiers have been called with
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* Tasks are frozen and the notifiers have been called with
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* PM_HIBERNATION_PREPARE
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* PM_HIBERNATION_PREPARE
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*/
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*/
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error = suspend_devices_and_enter(PM_SUSPEND_MEM);
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error = suspend_devices_and_enter(PM_SUSPEND_MEM);
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mutex_unlock(&pm_mutex);
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break;
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break;
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case SNAPSHOT_PLATFORM_SUPPORT:
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case SNAPSHOT_PLATFORM_SUPPORT:
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error = -ENOTTY;
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error = -ENOTTY;
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}
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}
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unlock_kernel();
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mutex_unlock(&pm_mutex);
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return error;
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return error;
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}
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}
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