From: Manfred Spraul <manfred@colorfullife.com>
SIGEV_THREAD means that a given callback should be called in the context on a
new thread. This must be done by the C library. The kernel must deliver a
notice of the event to the C library when the callback should be called.
This patch switches to a new, simpler interface: User space creates a socket
with socket(PF_NETLINK, SOCK_RAW,0) and passes the fd to the mq_notify call
together with a cookie. When the mq_notify() condition is satisfied, the
kernel "writes" the cookie to the socket. User space then reads the cookie
and calls the appropriate callback.
---
25-akpm/include/linux/mqueue.h | 16 ++
25-akpm/ipc/mqueue.c | 254 +++++++++++++++++------------------------
2 files changed, 123 insertions(+), 147 deletions(-)
diff -puN include/linux/mqueue.h~mq_notify-via-netlink include/linux/mqueue.h
--- 25/include/linux/mqueue.h~mq_notify-via-netlink Wed Apr 7 11:38:36 2004
+++ 25-akpm/include/linux/mqueue.h Wed Apr 7 11:38:36 2004
@@ -30,8 +30,24 @@ struct mq_attr {
long __reserved[4]; /* ignored for input, zeroed for output */
};
+/*
+ * SIGEV_THREAD implementation:
+ * SIGEV_THREAD must be implemented in user space. If SIGEV_THREAD is passed
+ * to mq_notify, then
+ * - sigev_signo must be the file descriptor of an AF_NETLINK socket. It's not
+ * necessary that the socket is bound.
+ * - sigev_value.sival_ptr must point to a cookie that is NOTIFY_COOKIE_LEN
+ * bytes long.
+ * If the notification is triggered, then the cookie is sent to the netlink
+ * socket. The last byte of the cookie is replaced with the NOTIFY_?? codes:
+ * NOTIFY_WOKENUP if the notification got triggered, NOTIFY_REMOVED if it was
+ * removed, either due to a close() on the message queue fd or due to a
+ * mq_notify() that removed the notification.
+ */
#define NOTIFY_NONE 0
#define NOTIFY_WOKENUP 1
#define NOTIFY_REMOVED 2
+#define NOTIFY_COOKIE_LEN 32
+
#endif
diff -puN ipc/mqueue.c~mq_notify-via-netlink ipc/mqueue.c
--- 25/ipc/mqueue.c~mq_notify-via-netlink Wed Apr 7 11:38:36 2004
+++ 25-akpm/ipc/mqueue.c Wed Apr 7 11:38:36 2004
@@ -20,6 +20,9 @@
#include <linux/poll.h>
#include <linux/mqueue.h>
#include <linux/msg.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <net/sock.h>
#include "util.h"
#define MQUEUE_MAGIC 0x19800202
@@ -33,9 +36,6 @@
#define STATE_PENDING 1
#define STATE_READY 2
-#define NP_NONE ((void*)NOTIFY_NONE)
-#define NP_WOKENUP ((void*)NOTIFY_WOKENUP)
-#define NP_REMOVED ((void*)NOTIFY_REMOVED)
/* used by sysctl */
#define FS_MQUEUE 1
#define CTL_QUEUESMAX 2
@@ -48,6 +48,8 @@
#define HARD_MSGMAX (131072/sizeof(void*))
#define DFLT_MSGSIZEMAX 16384 /* max message size */
+#define NOTIFY_COOKIE_LEN 32
+
struct ext_wait_queue { /* queue of sleeping tasks */
struct task_struct *task;
struct list_head list;
@@ -56,25 +58,26 @@ struct ext_wait_queue { /* queue of sle
};
struct mqueue_inode_info {
- struct mq_attr attr;
+ spinlock_t lock;
+ struct inode vfs_inode;
+ wait_queue_head_t wait_q;
+
struct msg_msg **messages;
+ struct mq_attr attr;
- pid_t notify_owner; /* != 0 means notification registered */
- struct sigevent notify;
- struct file *notify_filp;
+ struct sigevent notify; /* notify.sigev_notify == SIGEV_NONE means */
+ pid_t notify_owner; /* no notification registered */
+ struct sock *notify_sock;
+ struct sk_buff *notify_cookie;
/* for tasks waiting for free space and messages, respectively */
struct ext_wait_queue e_wait_q[2];
- wait_queue_head_t wait_q;
unsigned long qsize; /* size of queue in memory (sum of all msgs) */
- spinlock_t lock;
- struct inode vfs_inode;
};
static struct inode_operations mqueue_dir_inode_operations;
static struct file_operations mqueue_file_operations;
-static struct file_operations mqueue_notify_fops;
static struct super_operations mqueue_super_ops;
static void remove_notification(struct mqueue_inode_info *info);
@@ -119,7 +122,7 @@ static struct inode *mqueue_get_inode(st
init_waitqueue_head(&info->wait_q);
INIT_LIST_HEAD(&info->e_wait_q[0].list);
INIT_LIST_HEAD(&info->e_wait_q[1].list);
- info->notify_owner = 0;
+ info->notify.sigev_notify = SIGEV_NONE;
info->qsize = 0;
memset(&info->attr, 0, sizeof(info->attr));
info->attr.mq_maxmsg = DFLT_MSGMAX;
@@ -283,10 +286,11 @@ static ssize_t mqueue_read_file(struct f
snprintf(buffer, sizeof(buffer),
"QSIZE:%-10lu NOTIFY:%-5d SIGNO:%-5d NOTIFY_PID:%-6d\n",
info->qsize,
- info->notify_owner ? info->notify.sigev_notify : SIGEV_NONE,
- (info->notify_owner && info->notify.sigev_notify == SIGEV_SIGNAL ) ?
+ info->notify.sigev_notify,
+ (info->notify.sigev_notify == SIGEV_SIGNAL ) ?
info->notify.sigev_signo : 0,
- info->notify_owner);
+ (info->notify.sigev_notify != SIGEV_NONE) ?
+ info->notify_owner : 0);
spin_unlock(&info->lock);
buffer[sizeof(buffer)-1] = '\0';
slen = strlen(buffer)+1;
@@ -299,7 +303,7 @@ static ssize_t mqueue_read_file(struct f
count = slen - o;
if (copy_to_user(u_data, buffer + o, count))
- return -EFAULT;
+ return -EFAULT;
*off = o + count;
filp->f_dentry->d_inode->i_atime = filp->f_dentry->d_inode->i_ctime = CURRENT_TIME;
@@ -311,7 +315,8 @@ static int mqueue_flush_file(struct file
struct mqueue_inode_info *info = MQUEUE_I(filp->f_dentry->d_inode);
spin_lock(&info->lock);
- if (current->tgid == info->notify_owner)
+ if (info->notify.sigev_notify != SIGEV_NONE &&
+ current->tgid == info->notify_owner)
remove_notification(info);
spin_unlock(&info->lock);
@@ -435,6 +440,11 @@ static inline struct msg_msg *msg_get(st
return info->messages[info->attr.mq_curmsgs];
}
+static inline void set_cookie(struct sk_buff *skb, char code)
+{
+ ((char*)skb->data)[NOTIFY_COOKIE_LEN-1] = code;
+}
+
/*
* The next function is only to split too long sys_mq_timedsend
*/
@@ -445,7 +455,8 @@ static void __do_notify(struct mqueue_in
* waiting synchronously for message AND state of queue changed from
* empty to not empty. Here we are sure that no one is waiting
* synchronously. */
- if (info->notify_owner && info->attr.mq_curmsgs == 1) {
+ if (info->notify.sigev_notify != SIGEV_NONE &&
+ info->attr.mq_curmsgs == 1) {
/* sends signal */
if (info->notify.sigev_notify == SIGEV_SIGNAL) {
struct siginfo sig_i;
@@ -460,10 +471,12 @@ static void __do_notify(struct mqueue_in
kill_proc_info(info->notify.sigev_signo,
&sig_i, info->notify_owner);
} else if (info->notify.sigev_notify == SIGEV_THREAD) {
- info->notify_filp->private_data = (void*)NP_WOKENUP;
+ set_cookie(info->notify_cookie, NOTIFY_WOKENUP);
+ netlink_sendskb(info->notify_sock,
+ info->notify_cookie, 0);
}
/* after notification unregisters process */
- info->notify_owner = 0;
+ info->notify.sigev_notify = SIGEV_NONE;
}
wake_up(&info->wait_q);
}
@@ -499,90 +512,13 @@ static long prepare_timeout(const struct
return timeout;
}
-/*
- * File descriptor based notification, intended to be used to implement
- * SIGEV_THREAD:
- * SIGEV_THREAD means that a notification function should be called in the
- * context of a new thread. The kernel can't do that. Therefore mq_notify
- * calls with SIGEV_THREAD return a new file descriptor. A user space helper
- * must create a new thread and then read from the given file descriptor.
- * The read always returns one byte. If it's NOTIFY_WOKENUP, then it must
- * call the notification function. If it's NOTIFY_REMOVED, then the
- * notification was removed. The file descriptor supports poll, thus one
- * supervisor thread can manage multiple message queue notifications.
- *
- * The implementation must support multiple outstanding notifications:
- * It's possible that a new notification is added and signaled before user
- * space calls mqueue_notify_read for the previous notification.
- * Therefore the notification state is stored in the private_data field of
- * the file descriptor.
- */
-static unsigned int mqueue_notify_poll(struct file *filp,
- struct poll_table_struct *poll_tab)
-{
- struct mqueue_inode_info *info = MQUEUE_I(filp->f_dentry->d_inode);
- int retval;
-
- poll_wait(filp, &info->wait_q, poll_tab);
-
- if (filp->private_data == NP_NONE)
- retval = 0;
- else
- retval = POLLIN | POLLRDNORM;
- return retval;
-}
-
-static ssize_t mqueue_notify_read(struct file *filp, char __user *buf,
- size_t count, loff_t *ppos)
-{
- struct mqueue_inode_info *info = MQUEUE_I(filp->f_dentry->d_inode);
- char result;
-
- if (!count)
- return 0;
- if (*ppos != 0)
- return 0;
- spin_lock(&info->lock);
- while (filp->private_data == NP_NONE) {
- DEFINE_WAIT(wait);
- if (filp->f_flags & O_NONBLOCK) {
- spin_unlock(&info->lock);
- return -EAGAIN;
- }
- prepare_to_wait(&info->wait_q, &wait, TASK_INTERRUPTIBLE);
- spin_unlock(&info->lock);
- schedule();
- finish_wait(&info->wait_q, &wait);
- spin_lock(&info->lock);
- }
- spin_unlock(&info->lock);
- result = (char)(unsigned long)filp->private_data;
- if (put_user(result, buf))
- return -EFAULT;
- *ppos = 1;
- return 1;
-}
-
-static int mqueue_notify_release(struct inode *inode, struct file *filp)
-{
- struct mqueue_inode_info *info = MQUEUE_I(filp->f_dentry->d_inode);
-
- spin_lock(&info->lock);
- if (info->notify_owner && info->notify_filp == filp)
- info->notify_owner = 0;
- filp->private_data = NP_REMOVED;
- spin_unlock(&info->lock);
-
- return 0;
-}
-
static void remove_notification(struct mqueue_inode_info *info)
{
if (info->notify.sigev_notify == SIGEV_THREAD) {
- info->notify_filp->private_data = NP_REMOVED;
- wake_up(&info->wait_q);
+ set_cookie(info->notify_cookie, NOTIFY_REMOVED);
+ netlink_sendskb(info->notify_sock, info->notify_cookie, 0);
}
- info->notify_owner = 0;
+ info->notify.sigev_notify = SIGEV_NONE;
}
/*
@@ -780,7 +716,8 @@ out_unlock:
*/
/* pipelined_send() - send a message directly to the task waiting in
- * sys_mq_timedreceive() (without inserting message into a queue). */
+ * sys_mq_timedreceive() (without inserting message into a queue).
+ */
static inline void pipelined_send(struct mqueue_inode_info *info,
struct msg_msg *message,
struct ext_wait_queue *receiver)
@@ -974,12 +911,16 @@ out:
asmlinkage long sys_mq_notify(mqd_t mqdes,
const struct sigevent __user *u_notification)
{
- int ret, fd;
- struct file *filp, *nfilp;
+ int ret;
+ struct file *filp;
+ struct sock *sock;
struct inode *inode;
struct sigevent notification;
struct mqueue_inode_info *info;
+ struct sk_buff *nc;
+ nc = NULL;
+ sock = NULL;
if (u_notification == NULL) {
notification.sigev_notify = SIGEV_NONE;
} else {
@@ -996,6 +937,44 @@ asmlinkage long sys_mq_notify(mqd_t mqde
notification.sigev_signo > _NSIG)) {
return -EINVAL;
}
+ if (notification.sigev_notify == SIGEV_THREAD) {
+ /* create the notify skb */
+ nc = alloc_skb(NOTIFY_COOKIE_LEN, GFP_KERNEL);
+ ret = -ENOMEM;
+ if (!nc)
+ goto out;
+ ret = -EFAULT;
+ if (copy_from_user(nc->data,
+ notification.sigev_value.sival_ptr,
+ NOTIFY_COOKIE_LEN)) {
+ goto out;
+ }
+
+ /* TODO: add a header? */
+ skb_put(nc, NOTIFY_COOKIE_LEN);
+ /* and attach it to the socket */
+retry:
+ filp = fget(notification.sigev_signo);
+ ret = -EBADF;
+ if (!filp)
+ goto out;
+ sock = netlink_getsockbyfilp(filp);
+ fput(filp);
+ if (IS_ERR(sock)) {
+ ret = PTR_ERR(sock);
+ sock = NULL;
+ goto out;
+ }
+
+ ret = netlink_attachskb(sock, nc, 0, MAX_SCHEDULE_TIMEOUT);
+ if (ret == 1)
+ goto retry;
+ if (ret) {
+ sock = NULL;
+ nc = NULL;
+ goto out;
+ }
+ }
}
ret = -EBADF;
@@ -1009,47 +988,33 @@ asmlinkage long sys_mq_notify(mqd_t mqde
info = MQUEUE_I(inode);
ret = 0;
- if (notification.sigev_notify == SIGEV_THREAD) {
- ret = get_unused_fd();
- if (ret < 0)
- goto out_fput;
- fd = ret;
- nfilp = get_empty_filp();
- if (!nfilp) {
- ret = -ENFILE;
- goto out_dropfd;
- }
- nfilp->private_data = NP_NONE;
- nfilp->f_op = &mqueue_notify_fops;
- nfilp->f_vfsmnt = mntget(mqueue_mnt);
- nfilp->f_dentry = dget(filp->f_dentry);
- nfilp->f_mapping = filp->f_dentry->d_inode->i_mapping;
- nfilp->f_flags = O_RDONLY;
- nfilp->f_mode = FMODE_READ;
- } else {
- nfilp = NULL;
- fd = -1;
- }
-
spin_lock(&info->lock);
-
- if (notification.sigev_notify == SIGEV_NONE) {
- if (info->notify_owner == current->tgid) {
+ switch (notification.sigev_notify) {
+ case SIGEV_NONE:
+ if (info->notify.sigev_notify != SIGEV_NONE &&
+ info->notify_owner == current->tgid) {
remove_notification(info);
inode->i_atime = inode->i_ctime = CURRENT_TIME;
}
- } else if (info->notify_owner) {
- ret = -EBUSY;
- } else if (notification.sigev_notify == SIGEV_THREAD) {
- info->notify_filp = nfilp;
- fd_install(fd, nfilp);
- ret = fd;
- fd = -1;
- nfilp = NULL;
+ break;
+ case SIGEV_THREAD:
+ if (info->notify.sigev_notify != SIGEV_NONE) {
+ ret = -EBUSY;
+ break;
+ }
+ info->notify_sock = sock;
+ info->notify_cookie = nc;
+ sock = NULL;
+ nc = NULL;
info->notify.sigev_notify = SIGEV_THREAD;
info->notify_owner = current->tgid;
inode->i_atime = inode->i_ctime = CURRENT_TIME;
- } else {
+ break;
+ case SIGEV_SIGNAL:
+ if (info->notify.sigev_notify != SIGEV_NONE) {
+ ret = -EBUSY;
+ break;
+ }
info->notify.sigev_signo = notification.sigev_signo;
info->notify.sigev_value = notification.sigev_value;
info->notify.sigev_notify = SIGEV_SIGNAL;
@@ -1057,12 +1022,14 @@ asmlinkage long sys_mq_notify(mqd_t mqde
inode->i_atime = inode->i_ctime = CURRENT_TIME;
}
spin_unlock(&info->lock);
-out_dropfd:
- if (fd != -1)
- put_unused_fd(fd);
out_fput:
fput(filp);
out:
+ if (sock) {
+ netlink_detachskb(sock, nc);
+ } else if (nc) {
+ dev_kfree_skb(nc);
+ }
return ret;
}
@@ -1131,13 +1098,6 @@ static struct file_operations mqueue_fil
.read = mqueue_read_file,
};
-static struct file_operations mqueue_notify_fops = {
- .poll = mqueue_notify_poll,
- .read = mqueue_notify_read,
- .release = mqueue_notify_release,
-};
-
-
static struct super_operations mqueue_super_ops = {
.alloc_inode = mqueue_alloc_inode,
.destroy_inode = mqueue_destroy_inode,
_