random: add async notification support to /dev/random
Add async notification support to /dev/random.
A little test case is below. Without this patch, you get:
$ ./async-random
Drained the pool
Found more randomness
With it, you get:
$ ./async-random
Drained the pool
SIGIO
Found more randomness
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
static void handler(int sig)
{
printf("SIGIO\n");
}
int main(int argc, char **argv)
{
int fd, n, err, flags;
if(signal(SIGIO, handler) < 0){
perror("setting SIGIO handler");
exit(1);
}
fd = open("/dev/random", O_RDONLY);
if(fd < 0){
perror("open");
exit(1);
}
flags = fcntl(fd, F_GETFL);
if (flags < 0){
perror("getting flags");
exit(1);
}
flags |= O_NONBLOCK;
if (fcntl(fd, F_SETFL, flags) < 0){
perror("setting flags");
exit(1);
}
while((err = read(fd, &n, sizeof(n))) > 0) ;
if(err == 0){
printf("random returned 0\n");
exit(1);
}
else if(errno != EAGAIN){
perror("read");
exit(1);
}
flags |= O_ASYNC;
if (fcntl(fd, F_SETFL, flags) < 0){
perror("setting flags");
exit(1);
}
if (fcntl(fd, F_SETOWN, getpid()) < 0) {
perror("Setting SIGIO");
exit(1);
}
printf("Drained the pool\n");
read(fd, &n, sizeof(n));
printf("Found more randomness\n");
return(0);
}
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Matt Mackall <mpm@selenic.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 2faeef2..0cf98bd 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -370,6 +370,7 @@
*/
static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
+static struct fasync_struct *fasync;
#if 0
static int debug;
@@ -533,8 +534,11 @@
r->entropy_count = r->poolinfo->POOLBITS;
/* should we wake readers? */
- if (r == &input_pool && r->entropy_count >= random_read_wakeup_thresh)
+ if (r == &input_pool &&
+ r->entropy_count >= random_read_wakeup_thresh) {
wake_up_interruptible(&random_read_wait);
+ kill_fasync(&fasync, SIGIO, POLL_IN);
+ }
spin_unlock_irqrestore(&r->lock, flags);
}
@@ -742,8 +746,10 @@
else
r->entropy_count = reserved;
- if (r->entropy_count < random_write_wakeup_thresh)
+ if (r->entropy_count < random_write_wakeup_thresh) {
wake_up_interruptible(&random_write_wait);
+ kill_fasync(&fasync, SIGIO, POLL_OUT);
+ }
}
DEBUG_ENT("debiting %d entropy credits from %s%s\n",
@@ -1100,17 +1106,31 @@
}
}
+static int random_fasync(int fd, struct file *filp, int on)
+{
+ return fasync_helper(fd, filp, on, &fasync);
+}
+
+static int random_release(struct inode *inode, struct file *filp)
+{
+ return fasync_helper(-1, filp, 0, &fasync);
+}
+
const struct file_operations random_fops = {
.read = random_read,
.write = random_write,
.poll = random_poll,
.unlocked_ioctl = random_ioctl,
+ .fasync = random_fasync,
+ .release = random_release,
};
const struct file_operations urandom_fops = {
.read = urandom_read,
.write = random_write,
.unlocked_ioctl = random_ioctl,
+ .fasync = random_fasync,
+ .release = random_release,
};
/***************************************************************