3rd-party/linux-kernel-module-cheat
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Poll works!

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This commit is contained in:
Ciro Santilli
2017-06-08 06:24:07 +01:00
parent 36cd620dd2
commit 41dbf46531
4 changed files with 38 additions and 32 deletions
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41
kernel_module/poll.c
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@@ -1,9 +1,7 @@
/*
TODO now yet waiting for anything!
/poll.sh
Basic poll file_operation example.
Waits for a second, give jiffies to user, wait for a second...
Outcome: user echoes jiffies every second.
*/
#include <asm/uaccess.h> /* copy_from_user, copy_to_user */
@@ -21,37 +19,46 @@ Waits for a second, give jiffies to user, wait for a second...
MODULE_LICENSE("GPL");
static char readbuf[1024];
static size_t readbuflen;
static struct dentry *dir;
static struct task_struct *kthread;
static wait_queue_head_t waitqueue;
static ssize_t read(struct file *file, char __user *buf, size_t len, loff_t *off)
static ssize_t read(struct file *filp, char __user *buf, size_t len, loff_t *off)
{
ssize_t ret;
char s[1024];
ret = snprintf(s, sizeof(s), "%llu", (unsigned long long)jiffies);
if (copy_to_user(buf, s, ret)) {
if (copy_to_user(buf, readbuf, readbuflen)) {
ret = -EFAULT;
} else {
ret = readbuflen;
}
/* This is normal pipe behaviour: data gets drained once a reader reads from it. */
/* https://stackoverflow.com/questions/1634580/named-pipes-fifos-on-unix-with-multiple-readers */
readbuflen = 0;
return ret;
}
/*
If you return 0 here, then the kernel will sleep until an event happens in the queue.
This gets called again every time an event happens in the wait queue.
*/
unsigned int poll(struct file *filp, struct poll_table_struct *wait)
{
/*TODO*/
/*wait_event_interruptible(waitqueue, (dev->rp != dev->wp));*/
pr_info("poll_wait before\n");
poll_wait(filp, &waitqueue, wait);
pr_info("poll_wait after\n");
return POLLIN;
if (readbuflen)
return POLLIN;
else
return 0;
}
static int kthread_func(void *data)
{
while (!kthread_should_stop()) {
readbuflen = snprintf(readbuf, sizeof(readbuf), "%llu", (unsigned long long)jiffies);
usleep_range(1000000, 1000001);
wake_up_interruptible(&waitqueue);
wake_up(&waitqueue);
}
return 0;
}
@@ -64,14 +71,16 @@ static const struct file_operations fops = {
static int myinit(void)
{
dir = debugfs_create_dir("lkmc_poll", 0);
debugfs_create_file("f", 0666, dir, NULL, &fops);
debugfs_create_file("f", 0666, dir, NULL, &fops);
init_waitqueue_head(&waitqueue);
kthread = kthread_create(kthread_func, NULL, "mykthread");
wake_up_process(kthread);
return 0;
}
static void myexit(void)
{
kthread_stop(kthread);
debugfs_remove_recursive(dir);
}