---

yaml
---
r: 213507
b: refs/heads/master
c: 47725ac
h: refs/heads/master
i:
  213505: 8ad1906
  213503: 7e40893
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f4a3e0bceb57466c31757f25e4e0ed108d1299ec
+refs/heads/master: 47725ac76f51328d467b1430dfd027aba8706a11

trunk/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 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 	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;