Messages in this thread Patch in this message | | | Date | Mon, 21 Jan 2008 13:18:41 -0500 | From | Jeff Dike <> | Subject | [PATCH] random - add async I/O support |
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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> --- drivers/char/random.c | 43 +++++++++++++++++++++++++++++++++---------- 1 file changed, 33 insertions(+), 10 deletions(-)
Index: linux-2.6.22/drivers/char/random.c =================================================================== --- linux-2.6.22.orig/drivers/char/random.c 2008-01-17 12:51:07.000000000 -0500 +++ linux-2.6.22/drivers/char/random.c 2008-01-21 13:02:02.000000000 -0500 @@ -371,6 +371,8 @@ static struct poolinfo { 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 = 0; module_param(debug, bool, 0644); @@ -751,8 +753,10 @@ static size_t account(struct entropy_sto 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", @@ -1090,8 +1094,11 @@ random_ioctl(struct inode * inode, struc * Wake up waiting processes if we have enough * entropy. */ - if (input_pool.entropy_count >= random_read_wakeup_thresh) + if (input_pool.entropy_count >= random_read_wakeup_thresh) { wake_up_interruptible(&random_read_wait); + kill_fasync(&fasync, SIGIO, POLL_IN); + } + return 0; case RNDADDENTROPY: if (!capable(CAP_SYS_ADMIN)) @@ -1111,8 +1118,10 @@ random_ioctl(struct inode * inode, struc * Wake up waiting processes if we have enough * entropy. */ - if (input_pool.entropy_count >= random_read_wakeup_thresh) + if (input_pool.entropy_count >= random_read_wakeup_thresh) { wake_up_interruptible(&random_read_wait); + kill_fasync(&fasync, SIGIO, POLL_IN); + } return 0; case RNDZAPENTCNT: case RNDCLEARPOOL: @@ -1128,17 +1137,31 @@ random_ioctl(struct inode * inode, struc } } +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, - .ioctl = random_ioctl, + .read = random_read, + .write = random_write, + .poll = random_poll, + .ioctl = random_ioctl, + .fasync = random_fasync, + .release = random_release, }; const struct file_operations urandom_fops = { - .read = urandom_read, - .write = random_write, - .ioctl = random_ioctl, + .read = urandom_read, + .write = random_write, + .ioctl = random_ioctl, + .fasync = random_fasync, + .release = random_release, }; /***************************************************************
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