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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] Fix cancellation of pending watch events on watch unregistration.
# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 5134f3c512c8e140ca7454e27f1931870ca8b4d7
# Parent 03d69dbea1527720f11a358bf525efbb8c40aec7
Fix cancellation of pending watch events on watch unregistration.
Use wait_event_interruptible() so that our kernel threads spend
their time in the more acceptable 'S' state rather than the more
worrying 'D' state.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
diff -r 03d69dbea152 -r 5134f3c512c8
linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_comms.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_comms.c Mon Oct 10
15:57:41 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_comms.c Mon Oct 10
17:16:03 2005
@@ -128,7 +128,7 @@
void *dst;
unsigned int avail;
- wait_event(xb_waitq, output_avail(out));
+ wait_event_interruptible(xb_waitq, output_avail(out));
mb();
h = *out;
@@ -136,6 +136,8 @@
return -EIO;
dst = get_output_chunk(&h, out->buf, &avail);
+ if (avail == 0)
+ continue;
if (avail > len)
avail = len;
memcpy(dst, data, avail);
@@ -167,7 +169,7 @@
unsigned int avail;
const char *src;
- wait_event(xb_waitq, xs_input_avail());
+ wait_event_interruptible(xb_waitq, xs_input_avail());
mb();
h = *in;
@@ -175,6 +177,8 @@
return -EIO;
src = get_input_chunk(&h, in->buf, &avail);
+ if (avail == 0)
+ continue;
if (avail > len)
avail = len;
was_full = !output_avail(&h);
diff -r 03d69dbea152 -r 5134f3c512c8
linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c Mon Oct 10
15:57:41 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c Mon Oct 10
17:16:03 2005
@@ -43,9 +43,6 @@
static struct notifier_block *xenstore_chain;
-/* Now used to protect xenbus probes against save/restore. */
-static DECLARE_MUTEX(xenbus_lock);
-
/* If something in array of ids matches this device, return it. */
static const struct xenbus_device_id *
match_device(const struct xenbus_device_id *arr, struct xenbus_device *dev)
@@ -232,18 +229,13 @@
static int xenbus_register_driver_common(struct xenbus_driver *drv,
struct xen_bus_type *bus)
{
- int err;
-
drv->driver.name = drv->name;
drv->driver.bus = &bus->bus;
drv->driver.owner = drv->owner;
drv->driver.probe = xenbus_dev_probe;
drv->driver.remove = xenbus_dev_remove;
- down(&xenbus_lock);
- err = driver_register(&drv->driver);
- up(&xenbus_lock);
- return err;
+ return driver_register(&drv->driver);
}
int xenbus_register_driver(struct xenbus_driver *drv)
@@ -259,9 +251,7 @@
void xenbus_unregister_driver(struct xenbus_driver *drv)
{
- down(&xenbus_lock);
driver_unregister(&drv->driver);
- up(&xenbus_lock);
}
EXPORT_SYMBOL(xenbus_unregister_driver);
@@ -624,8 +614,6 @@
void xenbus_suspend(void)
{
- /* We keep lock, so no comms can happen as page moves. */
- down(&xenbus_lock);
bus_for_each_dev(&xenbus_frontend.bus, NULL, NULL, suspend_dev);
bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, suspend_dev);
xs_suspend();
@@ -637,14 +625,11 @@
xs_resume();
bus_for_each_dev(&xenbus_frontend.bus, NULL, NULL, resume_dev);
bus_for_each_dev(&xenbus_backend.bus, NULL, NULL, resume_dev);
- up(&xenbus_lock);
}
int register_xenstore_notifier(struct notifier_block *nb)
{
int ret = 0;
-
- down(&xenbus_lock);
if (xen_start_info->store_evtchn) {
ret = nb->notifier_call(nb, 0, NULL);
@@ -652,17 +637,13 @@
notifier_chain_register(&xenstore_chain, nb);
}
- up(&xenbus_lock);
-
return ret;
}
EXPORT_SYMBOL(register_xenstore_notifier);
void unregister_xenstore_notifier(struct notifier_block *nb)
{
- down(&xenbus_lock);
notifier_chain_unregister(&xenstore_chain, nb);
- up(&xenbus_lock);
}
EXPORT_SYMBOL(unregister_xenstore_notifier);
@@ -683,16 +664,16 @@
return err;
}
- down(&xenbus_lock);
/* Enumerate devices in xenstore. */
xenbus_probe_devices(&xenbus_frontend);
xenbus_probe_devices(&xenbus_backend);
+
/* Watch for changes. */
register_xenbus_watch(&fe_watch);
register_xenbus_watch(&be_watch);
+
/* Notify others that xenstore is up */
notifier_call_chain(&xenstore_chain, 0, 0);
- up(&xenbus_lock);
return 0;
}
diff -r 03d69dbea152 -r 5134f3c512c8
linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c Mon Oct 10
15:57:41 2005
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c Mon Oct 10
17:16:03 2005
@@ -43,18 +43,18 @@
#define streq(a, b) (strcmp((a), (b)) == 0)
struct xs_stored_msg {
+ struct list_head list;
+
struct xsd_sockmsg hdr;
union {
- /* Stored replies. */
+ /* Queued replies. */
struct {
- struct list_head list;
char *body;
} reply;
- /* Queued watch callbacks. */
+ /* Queued watch events. */
struct {
- struct work_struct work;
struct xenbus_watch *handle;
char **vec;
unsigned int vec_size;
@@ -77,9 +77,23 @@
static struct xs_handle xs_state;
+/* List of registered watches, and a lock to protect it. */
static LIST_HEAD(watches);
static DEFINE_SPINLOCK(watches_lock);
-static struct workqueue_struct *watches_workq;
+
+/* List of pending watch calbback events, and a lock to protect it. */
+static LIST_HEAD(watch_events);
+static DEFINE_SPINLOCK(watch_events_lock);
+
+/*
+ * Details of the xenwatch callback kernel thread. The thread waits on the
+ * watch_events_waitq for work to do (queued on watch_events list). When it
+ * wakes up it acquires the xenwatch_mutex before reading the list and
+ * carrying out work.
+ */
+static pid_t xenwatch_pid;
+static DECLARE_MUTEX(xenwatch_mutex);
+static DECLARE_WAIT_QUEUE_HEAD(watch_events_waitq);
static int get_error(const char *errorstring)
{
@@ -105,14 +119,14 @@
while (list_empty(&xs_state.reply_list)) {
spin_unlock(&xs_state.reply_lock);
- wait_event(xs_state.reply_waitq,
- !list_empty(&xs_state.reply_list));
+ wait_event_interruptible(xs_state.reply_waitq,
+ !list_empty(&xs_state.reply_list));
spin_lock(&xs_state.reply_lock);
}
msg = list_entry(xs_state.reply_list.next,
- struct xs_stored_msg, u.reply.list);
- list_del(&msg->u.reply.list);
+ struct xs_stored_msg, list);
+ list_del(&msg->list);
spin_unlock(&xs_state.reply_lock);
@@ -606,6 +620,7 @@
void unregister_xenbus_watch(struct xenbus_watch *watch)
{
+ struct xs_stored_msg *msg, *tmp;
char token[sizeof(watch) * 2 + 1];
int err;
@@ -626,8 +641,22 @@
up_read(&xs_state.suspend_mutex);
- /* Make sure watch is not in use. */
- flush_workqueue(watches_workq);
+ /* Cancel pending watch events. */
+ spin_lock(&watch_events_lock);
+ list_for_each_entry_safe(msg, tmp, &watch_events, list) {
+ if (msg->u.watch.handle != watch)
+ continue;
+ list_del(&msg->list);
+ kfree(msg->u.watch.vec);
+ kfree(msg);
+ }
+ spin_unlock(&watch_events_lock);
+
+ /* Flush any currently-executing callback, unless we are it. :-) */
+ if (current->pid != xenwatch_pid) {
+ down(&xenwatch_mutex);
+ up(&xenwatch_mutex);
+ }
}
EXPORT_SYMBOL(unregister_xenbus_watch);
@@ -653,16 +682,35 @@
up_write(&xs_state.suspend_mutex);
}
-static void xenbus_fire_watch(void *arg)
-{
- struct xs_stored_msg *msg = arg;
-
- msg->u.watch.handle->callback(msg->u.watch.handle,
- (const char **)msg->u.watch.vec,
- msg->u.watch.vec_size);
-
- kfree(msg->u.watch.vec);
- kfree(msg);
+static int xenwatch_thread(void *unused)
+{
+ struct list_head *ent;
+ struct xs_stored_msg *msg;
+
+ for (;;) {
+ wait_event_interruptible(watch_events_waitq,
+ !list_empty(&watch_events));
+
+ down(&xenwatch_mutex);
+
+ spin_lock(&watch_events_lock);
+ ent = watch_events.next;
+ if (ent != &watch_events)
+ list_del(ent);
+ spin_unlock(&watch_events_lock);
+
+ if (ent != &watch_events) {
+ msg = list_entry(ent, struct xs_stored_msg, list);
+ msg->u.watch.handle->callback(
+ msg->u.watch.handle,
+ (const char **)msg->u.watch.vec,
+ msg->u.watch.vec_size);
+ kfree(msg->u.watch.vec);
+ kfree(msg);
+ }
+
+ up(&xenwatch_mutex);
+ }
}
static int process_msg(void)
@@ -696,8 +744,6 @@
body[msg->hdr.len] = '\0';
if (msg->hdr.type == XS_WATCH_EVENT) {
- INIT_WORK(&msg->u.watch.work, xenbus_fire_watch, msg);
-
msg->u.watch.vec = split(body, msg->hdr.len,
&msg->u.watch.vec_size);
if (IS_ERR(msg->u.watch.vec)) {
@@ -709,7 +755,10 @@
msg->u.watch.handle = find_watch(
msg->u.watch.vec[XS_WATCH_TOKEN]);
if (msg->u.watch.handle != NULL) {
- queue_work(watches_workq, &msg->u.watch.work);
+ spin_lock(&watch_events_lock);
+ list_add_tail(&msg->list, &watch_events);
+ wake_up(&watch_events_waitq);
+ spin_unlock(&watch_events_lock);
} else {
kfree(msg->u.watch.vec);
kfree(msg);
@@ -718,7 +767,7 @@
} else {
msg->u.reply.body = body;
spin_lock(&xs_state.reply_lock);
- list_add_tail(&msg->u.reply.list, &xs_state.reply_list);
+ list_add_tail(&msg->list, &xs_state.reply_list);
spin_unlock(&xs_state.reply_lock);
wake_up(&xs_state.reply_waitq);
}
@@ -726,7 +775,7 @@
return 0;
}
-static int read_thread(void *unused)
+static int xenbus_thread(void *unused)
{
int err;
@@ -741,7 +790,7 @@
int xs_init(void)
{
int err;
- struct task_struct *reader;
+ struct task_struct *task;
INIT_LIST_HEAD(&xs_state.reply_list);
spin_lock_init(&xs_state.reply_lock);
@@ -755,13 +804,14 @@
if (err)
return err;
- /* Create our own workqueue for executing watch callbacks. */
- watches_workq = create_singlethread_workqueue("xenwatch");
- BUG_ON(watches_workq == NULL);
-
- reader = kthread_run(read_thread, NULL, "xenbus");
- if (IS_ERR(reader))
- return PTR_ERR(reader);
+ task = kthread_run(xenwatch_thread, NULL, "xenwatch");
+ if (IS_ERR(task))
+ return PTR_ERR(task);
+ xenwatch_pid = task->pid;
+
+ task = kthread_run(xenbus_thread, NULL, "xenbus");
+ if (IS_ERR(task))
+ return PTR_ERR(task);
return 0;
}
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