From: Manfred Spraul <manfred@colorfullife.com>
Here are the updates to the patch-mq-03-core:
It fixes the bug with the notification descriptors and adds more
documentation. What's still missing is a description of the change to
signal.c.
---
25-akpm/init/Kconfig | 1
25-akpm/ipc/mqueue.c | 141 +++++++++++++++++++++++++++++++++++++--------------
2 files changed, 105 insertions(+), 37 deletions(-)
diff -puN init/Kconfig~mq-03-core-update init/Kconfig
--- 25/init/Kconfig~mq-03-core-update 2004-03-24 02:51:57.661129048 -0800
+++ 25-akpm/init/Kconfig 2004-03-24 02:51:57.664128592 -0800
@@ -92,6 +92,7 @@ config SYSVIPC
config POSIX_MQUEUE
bool "POSIX Message Queues"
+ depends on EXPERIMENTAL
---help---
POSIX variant of message queues is a part of IPC. In POSIX message
queues every message has a priority which decides about succession
diff -puN ipc/mqueue.c~mq-03-core-update ipc/mqueue.c
--- 25/ipc/mqueue.c~mq-03-core-update 2004-03-24 02:51:57.662128896 -0800
+++ 25-akpm/ipc/mqueue.c 2004-03-24 02:51:57.667128136 -0800
@@ -105,7 +105,8 @@ static struct inode *mqueue_get_inode(st
inode->i_gid = current->fsgid;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
- inode->i_mtime = inode->i_ctime = inode->i_atime = CURRENT_TIME;
+ inode->i_mtime = inode->i_ctime = inode->i_atime =
+ CURRENT_TIME;
if (S_ISREG(mode)) {
struct mqueue_inode_info *info;
@@ -166,7 +167,7 @@ static void init_once(void *foo, kmem_ca
struct mqueue_inode_info *p = (struct mqueue_inode_info *) foo;
if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
- SLAB_CTOR_CONSTRUCTOR)
+ SLAB_CTOR_CONSTRUCTOR)
inode_init_once(&p->vfs_inode);
}
@@ -174,7 +175,7 @@ static struct inode *mqueue_alloc_inode(
{
struct mqueue_inode_info *ei;
- ei = (struct mqueue_inode_info *)kmem_cache_alloc(mqueue_inode_cachep, SLAB_KERNEL);
+ ei = kmem_cache_alloc(mqueue_inode_cachep, SLAB_KERNEL);
if (!ei)
return NULL;
return &ei->vfs_inode;
@@ -208,7 +209,8 @@ static void mqueue_delete_inode(struct i
spin_unlock(&mq_lock);
}
-static int mqueue_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
+static int mqueue_create(struct inode *dir, struct dentry *dentry,
+ int mode, struct nameidata *nd)
{
struct inode *inode;
int error;
@@ -272,7 +274,7 @@ static void wq_add(struct mqueue_inode_i
* sr: SEND or RECV
*/
static int wq_sleep(struct mqueue_inode_info *info, int sr,
- long timeout, struct ext_wait_queue *ewp)
+ long timeout, struct ext_wait_queue *ewp)
{
int retval;
signed long time;
@@ -305,7 +307,6 @@ static int wq_sleep(struct mqueue_inode_
retval = -ETIMEDOUT;
break;
}
- printk(KERN_WARNING "mqueue: Spurious wakeup in wq_sleep()\n");
}
list_del(&ewp->list);
out_unlock:
@@ -314,7 +315,9 @@ out:
return retval;
}
-/* Returns waiting task that should be serviced first or NULL if none exists */
+/*
+ * Returns waiting task that should be serviced first or NULL if none exists
+ */
static struct ext_wait_queue *wq_get_first_waiter(
struct mqueue_inode_info *info, int sr)
{
@@ -386,7 +389,8 @@ static long prepare_timeout(const struct
long timeout;
if (u_arg) {
- if (unlikely(copy_from_user(&ts, u_arg, sizeof(struct timespec))))
+ if (unlikely(copy_from_user(&ts, u_arg,
+ sizeof(struct timespec))))
return -EFAULT;
if (unlikely(ts.tv_nsec < 0 || ts.tv_sec < 0
@@ -410,7 +414,26 @@ static long prepare_timeout(const struct
return timeout;
}
-static unsigned int mqueue_notify_poll(struct file *filp, struct poll_table_struct *poll_tab)
+/*
+ * 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;
@@ -424,7 +447,8 @@ static unsigned int mqueue_notify_poll(s
return retval;
}
-static ssize_t mqueue_notify_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
+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;
@@ -454,6 +478,19 @@ static ssize_t mqueue_notify_read(struct
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) {
@@ -467,7 +504,7 @@ static void remove_notification(struct m
* Invoked when creating a new queue via sys_mq_open
*/
static struct file *do_create(struct dentry *dir, struct dentry *dentry,
- int oflag, mode_t mode, struct mq_attr __user *u_attr)
+ int oflag, mode_t mode, struct mq_attr __user *u_attr)
{
struct file *filp;
struct inode *inode;
@@ -486,7 +523,8 @@ static struct file *do_create(struct den
if (attr.mq_maxmsg > HARD_MSGMAX)
return ERR_PTR(-EINVAL);
} else {
- if (attr.mq_maxmsg > msg_max || attr.mq_msgsize > msgsize_max)
+ if (attr.mq_maxmsg > msg_max ||
+ attr.mq_msgsize > msgsize_max)
return ERR_PTR(-EINVAL);
}
} else {
@@ -520,8 +558,9 @@ static struct file *do_create(struct den
/* Opens existing queue */
static struct file *do_open(struct dentry *dentry, int oflag)
{
+static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
+ MAY_READ | MAY_WRITE };
struct file *filp;
- static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE, MAY_READ | MAY_WRITE };
if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY))
return ERR_PTR(-EINVAL);
@@ -538,12 +577,12 @@ static struct file *do_open(struct dentr
}
asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,
- struct mq_attr __user *u_attr)
+ struct mq_attr __user *u_attr)
{
struct dentry *dentry;
struct file *filp;
- char *name;
- int fd, error;
+ char *name;
+ int fd, error;
if (IS_ERR(name = getname(u_name)))
return PTR_ERR(name);
@@ -562,12 +601,15 @@ asmlinkage long sys_mq_open(const char _
if (oflag & O_CREAT) {
if (dentry->d_inode) { /* entry already exists */
- filp = (oflag & O_EXCL) ? ERR_PTR(-EEXIST) : do_open(dentry, oflag);
+ filp = (oflag & O_EXCL) ? ERR_PTR(-EEXIST) :
+ do_open(dentry, oflag);
} else {
- filp = do_create(mqueue_mnt->mnt_root, dentry, oflag, mode, u_attr);
+ filp = do_create(mqueue_mnt->mnt_root, dentry,
+ oflag, mode, u_attr);
}
} else
- filp = (dentry->d_inode) ? do_open(dentry, oflag) : ERR_PTR(-ENOENT);
+ filp = (dentry->d_inode) ? do_open(dentry, oflag) :
+ ERR_PTR(-ENOENT);
dput(dentry);
@@ -635,8 +677,20 @@ out_unlock:
return err;
}
-/* Pipelined send and receive functions. Do not confuse this with SysV message
- * queues terminology. It is little bit different. */
+/* Pipelined send and receive functions.
+ *
+ * If a receiver finds no waiting message, then it registers itself in the
+ * list of waiting receivers. A sender checks that list before adding the new
+ * message into the message array. If there is a waiting receiver, then it
+ * bypasses the message array and directly hands the message over to the
+ * receiver.
+ * The receiver accepts the message and returns without grabbing the queue
+ * spinlock. Therefore an intermediate STATE_PENDING state and memory barriers
+ * are necessary. The same algorithm is used for sysv semaphores, see
+ * ipc/sem.c fore more details.
+ *
+ * The same algorithm is used for senders.
+ */
/* pipelined_send() - send a message directly to the task waiting in
* sys_mq_timedreceive() (without inserting message into a queue). */
@@ -670,7 +724,8 @@ static inline void pipelined_receive(str
}
asmlinkage long sys_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
- size_t msg_len, unsigned int msg_prio, const struct timespec __user *u_abs_timeout)
+ size_t msg_len, unsigned int msg_prio,
+ const struct timespec __user *u_abs_timeout)
{
struct file *filp;
struct inode *inode;
@@ -678,7 +733,7 @@ asmlinkage long sys_mq_timedsend(mqd_t m
struct ext_wait_queue *receiver;
struct msg_msg *msg_ptr;
struct mqueue_inode_info *info;
- long timeout;
+ long timeout;
int ret;
if (unlikely(msg_prio >= (unsigned long) MQ_PRIO_MAX))
@@ -738,7 +793,8 @@ asmlinkage long sys_mq_timedsend(mqd_t m
msg_insert(msg_ptr, info);
__do_notify(info);
}
- inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+ inode->i_atime = inode->i_mtime = inode->i_ctime =
+ CURRENT_TIME;
spin_unlock(&info->lock);
ret = 0;
}
@@ -798,7 +854,8 @@ asmlinkage ssize_t sys_mq_timedreceive(m
} else {
msg_ptr = msg_get(info);
- inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+ inode->i_atime = inode->i_mtime = inode->i_ctime =
+ CURRENT_TIME;
/* There is now free space in queue. */
pipelined_receive(info);
@@ -820,11 +877,13 @@ out:
return ret;
}
-/* Notes: the case when user wants us to deregister (with NULL as pointer or SIGEV_NONE)
- * and he isn't currently owner of notification will be silently discarded.
- * It isn't explicitly defined in the POSIX.
+/*
+ * Notes: the case when user wants us to deregister (with NULL as pointer
+ * or SIGEV_NONE) and he isn't currently owner of notification will be
+ * silently discarded. It isn't explicitly defined in the POSIX.
*/
-asmlinkage long sys_mq_notify(mqd_t mqdes, const struct sigevent __user *u_notification)
+asmlinkage long sys_mq_notify(mqd_t mqdes,
+ const struct sigevent __user *u_notification)
{
int ret, fd;
struct file *filp, *nfilp;
@@ -835,7 +894,8 @@ asmlinkage long sys_mq_notify(mqd_t mqde
if (u_notification == NULL) {
notification.sigev_notify = SIGEV_NONE;
} else {
- if (copy_from_user(¬ification, u_notification, sizeof(struct sigevent)))
+ if (copy_from_user(¬ification, u_notification,
+ sizeof(struct sigevent)))
return -EFAULT;
if (unlikely(notification.sigev_notify != SIGEV_NONE &&
@@ -843,7 +903,8 @@ asmlinkage long sys_mq_notify(mqd_t mqde
notification.sigev_notify != SIGEV_THREAD))
return -EINVAL;
if (notification.sigev_notify == SIGEV_SIGNAL &&
- (notification.sigev_signo < 0 || notification.sigev_signo > _NSIG)) {
+ (notification.sigev_signo < 0 ||
+ notification.sigev_signo > _NSIG)) {
return -EINVAL;
}
}
@@ -915,8 +976,9 @@ out:
return ret;
}
-asmlinkage long sys_mq_getsetattr(mqd_t mqdes, const struct mq_attr __user *u_mqstat,
- struct mq_attr __user *u_omqstat)
+asmlinkage long sys_mq_getsetattr(mqd_t mqdes,
+ const struct mq_attr __user *u_mqstat,
+ struct mq_attr __user *u_omqstat)
{
int ret;
struct mq_attr mqstat, omqstat;
@@ -955,7 +1017,8 @@ asmlinkage long sys_mq_getsetattr(mqd_t
spin_unlock(&info->lock);
ret = 0;
- if (u_omqstat != NULL && copy_to_user(u_omqstat, &omqstat, sizeof(struct mq_attr)))
+ if (u_omqstat != NULL && copy_to_user(u_omqstat, &omqstat,
+ sizeof(struct mq_attr)))
ret = -EFAULT;
out_fput:
@@ -977,6 +1040,7 @@ static struct file_operations mqueue_fil
static struct file_operations mqueue_notify_fops = {
.poll = mqueue_notify_poll,
.read = mqueue_notify_read,
+ .release = mqueue_notify_release,
};
@@ -1056,7 +1120,8 @@ static int __init init_mqueue_fs(void)
int error;
mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
- sizeof(struct mqueue_inode_info), 0, SLAB_HWCACHE_ALIGN, init_once, NULL);
+ sizeof(struct mqueue_inode_info), 0,
+ SLAB_HWCACHE_ALIGN, init_once, NULL);
if (mqueue_inode_cachep == NULL)
return -ENOMEM;
@@ -1086,8 +1151,10 @@ out_filesystem:
out_sysctl:
unregister_sysctl_table(mq_sysctl_table);
out_cache:
- if (kmem_cache_destroy(mqueue_inode_cachep))
- printk(KERN_INFO "mqueue_inode_cache: not all structures were freed\n");
+ if (kmem_cache_destroy(mqueue_inode_cachep)) {
+ printk(KERN_INFO
+ "mqueue_inode_cache: not all structures were freed\n");
+ }
return error;
}
_