diff options
| -rw-r--r-- | drivers/char/vc_screen.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/drivers/char/vc_screen.c b/drivers/char/vc_screen.c index bcce46c96b88..6f7054e1a516 100644 --- a/drivers/char/vc_screen.c +++ b/drivers/char/vc_screen.c @@ -35,6 +35,12 @@ #include <linux/console.h> #include <linux/device.h> #include <linux/smp_lock.h> +#include <linux/sched.h> +#include <linux/fs.h> +#include <linux/poll.h> +#include <linux/signal.h> +#include <linux/slab.h> +#include <linux/notifier.h> #include <asm/uaccess.h> #include <asm/byteorder.h> @@ -45,6 +51,86 @@ #undef addr #define HEADER_SIZE 4 +struct vcs_poll_data { + struct notifier_block notifier; + unsigned int cons_num; + bool seen_last_update; + wait_queue_head_t waitq; + struct fasync_struct *fasync; +}; + +static int +vcs_notifier(struct notifier_block *nb, unsigned long code, void *_param) +{ + struct vt_notifier_param *param = _param; + struct vc_data *vc = param->vc; + struct vcs_poll_data *poll = + container_of(nb, struct vcs_poll_data, notifier); + int currcons = poll->cons_num; + + if (code != VT_UPDATE) + return NOTIFY_DONE; + + if (currcons == 0) + currcons = fg_console; + else + currcons--; + if (currcons != vc->vc_num) + return NOTIFY_DONE; + + poll->seen_last_update = false; + wake_up_interruptible(&poll->waitq); + kill_fasync(&poll->fasync, SIGIO, POLL_IN); + return NOTIFY_OK; +} + +static void +vcs_poll_data_free(struct vcs_poll_data *poll) +{ + unregister_vt_notifier(&poll->notifier); + kfree(poll); +} + +static struct vcs_poll_data * +vcs_poll_data_get(struct file *file) +{ + struct vcs_poll_data *poll = file->private_data; + + if (poll) + return poll; + + poll = kzalloc(sizeof(*poll), GFP_KERNEL); + if (!poll) + return NULL; + poll->cons_num = iminor(file->f_path.dentry->d_inode) & 127; + init_waitqueue_head(&poll->waitq); + poll->notifier.notifier_call = vcs_notifier; + if (register_vt_notifier(&poll->notifier) != 0) { + kfree(poll); + return NULL; + } + + /* + * This code may be called either through ->poll() or ->fasync(). + * If we have two threads using the same file descriptor, they could + * both enter this function, both notice that the structure hasn't + * been allocated yet and go ahead allocating it in parallel, but + * only one of them must survive and be shared otherwise we'd leak + * memory with a dangling notifier callback. + */ + spin_lock(&file->f_lock); + if (!file->private_data) { + file->private_data = poll; + } else { + /* someone else raced ahead of us */ + vcs_poll_data_free(poll); + poll = file->private_data; + } + spin_unlock(&file->f_lock); + + return poll; +} + static int vcs_size(struct inode *inode) { @@ -102,6 +188,7 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) struct inode *inode = file->f_path.dentry->d_inode; unsigned int currcons = iminor(inode); struct vc_data *vc; + struct vcs_poll_data *poll; long pos; long viewed, attr, read; int col, maxcol; @@ -134,6 +221,9 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) ret = -EINVAL; if (pos < 0) goto unlock_out; + poll = file->private_data; + if (count && poll) + poll->seen_last_update = true; read = 0; ret = 0; while (count) { @@ -457,6 +547,37 @@ unlock_out: return ret; } +static unsigned int +vcs_poll(struct file *file, poll_table *wait) +{ + struct vcs_poll_data *poll = vcs_poll_data_get(file); + int ret = 0; + + if (poll) { + poll_wait(file, &poll->waitq, wait); + if (!poll->seen_last_update) + ret = POLLIN | POLLRDNORM; + } + return ret; +} + +static int +vcs_fasync(int fd, struct file *file, int on) +{ + struct vcs_poll_data *poll = file->private_data; + + if (!poll) { + /* don't allocate anything if all we want is disable fasync */ + if (!on) + return 0; + poll = vcs_poll_data_get(file); + if (!poll) + return -ENOMEM; + } + + return fasync_helper(fd, file, on, &poll->fasync); +} + static int vcs_open(struct inode *inode, struct file *filp) { @@ -470,11 +591,23 @@ vcs_open(struct inode *inode, struct file *filp) return ret; } +static int vcs_release(struct inode *inode, struct file *file) +{ + struct vcs_poll_data *poll = file->private_data; + + if (poll) + vcs_poll_data_free(poll); + return 0; +} + static const struct file_operations vcs_fops = { .llseek = vcs_lseek, .read = vcs_read, .write = vcs_write, + .poll = vcs_poll, + .fasync = vcs_fasync, .open = vcs_open, + .release = vcs_release, }; static struct class *vc_class; |