#include <linux/slab.h>
#include <linux/fcntl.h>
#include <linux/kthread.h>
+#include <linux/reboot.h>
#include <linux/rwsem.h>
#include <linux/mutex.h>
#include <asm/xen/hypervisor.h>
#include <xen/xenbus.h>
#include <xen/xen.h>
-#include "xenbus_comms.h"
-#include "xenbus_probe.h"
-
-struct xs_stored_msg {
- struct list_head list;
-
- struct xsd_sockmsg hdr;
-
- union {
- /* Queued replies. */
- struct {
- char *body;
- } reply;
-
- /* Queued watch events. */
- struct {
- struct xenbus_watch *handle;
- char **vec;
- unsigned int vec_size;
- } watch;
- } u;
-};
+#include "xenbus.h"
-struct xs_handle {
- /* A list of replies. Currently only one will ever be outstanding. */
- struct list_head reply_list;
- spinlock_t reply_lock;
- wait_queue_head_t reply_waitq;
-
- /*
- * Mutex ordering: transaction_mutex -> watch_mutex -> request_mutex.
- * response_mutex is never taken simultaneously with the other three.
- *
- * transaction_mutex must be held before incrementing
- * transaction_count. The mutex is held when a suspend is in
- * progress to prevent new transactions starting.
- *
- * When decrementing transaction_count to zero the wait queue
- * should be woken up, the suspend code waits for count to
- * reach zero.
- */
-
- /* One request at a time. */
- struct mutex request_mutex;
-
- /* Protect xenbus reader thread against save/restore. */
- struct mutex response_mutex;
-
- /* Protect transactions against save/restore. */
- struct mutex transaction_mutex;
- atomic_t transaction_count;
- wait_queue_head_t transaction_wq;
-
- /* Protect watch (de)register against save/restore. */
- struct rw_semaphore watch_mutex;
-};
+/*
+ * Framework to protect suspend/resume handling against normal Xenstore
+ * message handling:
+ * During suspend/resume there must be no open transaction and no pending
+ * Xenstore request.
+ * New watch events happening in this time can be ignored by firing all watches
+ * after resume.
+ */
+
+/* Lock protecting enter/exit critical region. */
+static DEFINE_SPINLOCK(xs_state_lock);
+/* Number of users in critical region (protected by xs_state_lock). */
+static unsigned int xs_state_users;
+/* Suspend handler waiting or already active (protected by xs_state_lock)? */
+static int xs_suspend_active;
+/* Unique Xenstore request id (protected by xs_state_lock). */
+static uint32_t xs_request_id;
-static struct xs_handle xs_state;
+/* Wait queue for all callers waiting for critical region to become usable. */
+static DECLARE_WAIT_QUEUE_HEAD(xs_state_enter_wq);
+/* Wait queue for suspend handling waiting for critical region being empty. */
+static DECLARE_WAIT_QUEUE_HEAD(xs_state_exit_wq);
/* List of registered watches, and a lock to protect it. */
static LIST_HEAD(watches);
static LIST_HEAD(watch_events);
static DEFINE_SPINLOCK(watch_events_lock);
+/* Protect watch (de)register against save/restore. */
+static DECLARE_RWSEM(xs_watch_rwsem);
+
/*
* 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
static DEFINE_MUTEX(xenwatch_mutex);
static DECLARE_WAIT_QUEUE_HEAD(watch_events_waitq);
+static void xs_suspend_enter(void)
+{
+ spin_lock(&xs_state_lock);
+ xs_suspend_active++;
+ spin_unlock(&xs_state_lock);
+ wait_event(xs_state_exit_wq, xs_state_users == 0);
+}
+
+static void xs_suspend_exit(void)
+{
+ spin_lock(&xs_state_lock);
+ xs_suspend_active--;
+ spin_unlock(&xs_state_lock);
+ wake_up_all(&xs_state_enter_wq);
+}
+
+static uint32_t xs_request_enter(struct xb_req_data *req)
+{
+ uint32_t rq_id;
+
+ req->type = req->msg.type;
+
+ spin_lock(&xs_state_lock);
+
+ while (!xs_state_users && xs_suspend_active) {
+ spin_unlock(&xs_state_lock);
+ wait_event(xs_state_enter_wq, xs_suspend_active == 0);
+ spin_lock(&xs_state_lock);
+ }
+
+ if (req->type == XS_TRANSACTION_START)
+ xs_state_users++;
+ xs_state_users++;
+ rq_id = xs_request_id++;
+
+ spin_unlock(&xs_state_lock);
+
+ return rq_id;
+}
+
+void xs_request_exit(struct xb_req_data *req)
+{
+ spin_lock(&xs_state_lock);
+ xs_state_users--;
+ if ((req->type == XS_TRANSACTION_START && req->msg.type == XS_ERROR) ||
+ req->type == XS_TRANSACTION_END)
+ xs_state_users--;
+ spin_unlock(&xs_state_lock);
+
+ if (xs_suspend_active && !xs_state_users)
+ wake_up(&xs_state_exit_wq);
+}
+
static int get_error(const char *errorstring)
{
unsigned int i;
}
return false;
}
-static void *read_reply(enum xsd_sockmsg_type *type, unsigned int *len)
+
+static bool test_reply(struct xb_req_data *req)
{
- struct xs_stored_msg *msg;
- char *body;
+ if (req->state == xb_req_state_got_reply || !xenbus_ok())
+ return true;
+
+ /* Make sure to reread req->state each time. */
+ barrier();
- spin_lock(&xs_state.reply_lock);
+ return false;
+}
+
+static void *read_reply(struct xb_req_data *req)
+{
+ while (req->state != xb_req_state_got_reply) {
+ wait_event(req->wq, test_reply(req));
- while (list_empty(&xs_state.reply_list)) {
- spin_unlock(&xs_state.reply_lock);
- if (xenbus_ok())
- /* XXX FIXME: Avoid synchronous wait for response here. */
- wait_event_timeout(xs_state.reply_waitq,
- !list_empty(&xs_state.reply_list),
- msecs_to_jiffies(500));
- else {
+ if (!xenbus_ok())
/*
* If we are in the process of being shut-down there is
* no point of trying to contact XenBus - it is either
* has been killed or is unreachable.
*/
return ERR_PTR(-EIO);
- }
- spin_lock(&xs_state.reply_lock);
+ if (req->err)
+ return ERR_PTR(req->err);
+
}
- msg = list_entry(xs_state.reply_list.next,
- struct xs_stored_msg, list);
- list_del(&msg->list);
+ return req->body;
+}
- spin_unlock(&xs_state.reply_lock);
+static void xs_send(struct xb_req_data *req, struct xsd_sockmsg *msg)
+{
+ bool notify;
- *type = msg->hdr.type;
- if (len)
- *len = msg->hdr.len;
- body = msg->u.reply.body;
+ req->msg = *msg;
+ req->err = 0;
+ req->state = xb_req_state_queued;
+ init_waitqueue_head(&req->wq);
- kfree(msg);
+ req->msg.req_id = xs_request_enter(req);
- return body;
-}
+ mutex_lock(&xb_write_mutex);
+ list_add_tail(&req->list, &xb_write_list);
+ notify = list_is_singular(&xb_write_list);
+ mutex_unlock(&xb_write_mutex);
-static void transaction_start(void)
-{
- mutex_lock(&xs_state.transaction_mutex);
- atomic_inc(&xs_state.transaction_count);
- mutex_unlock(&xs_state.transaction_mutex);
+ if (notify)
+ wake_up(&xb_waitq);
}
-static void transaction_end(void)
+static void *xs_wait_for_reply(struct xb_req_data *req, struct xsd_sockmsg *msg)
{
- if (atomic_dec_and_test(&xs_state.transaction_count))
- wake_up(&xs_state.transaction_wq);
-}
+ void *ret;
-static void transaction_suspend(void)
-{
- mutex_lock(&xs_state.transaction_mutex);
- wait_event(xs_state.transaction_wq,
- atomic_read(&xs_state.transaction_count) == 0);
+ ret = read_reply(req);
+
+ xs_request_exit(req);
+
+ msg->type = req->msg.type;
+ msg->len = req->msg.len;
+
+ mutex_lock(&xb_write_mutex);
+ if (req->state == xb_req_state_queued ||
+ req->state == xb_req_state_wait_reply)
+ req->state = xb_req_state_aborted;
+ else
+ kfree(req);
+ mutex_unlock(&xb_write_mutex);
+
+ return ret;
}
-static void transaction_resume(void)
+static void xs_wake_up(struct xb_req_data *req)
{
- mutex_unlock(&xs_state.transaction_mutex);
+ wake_up(&req->wq);
}
-void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg)
+int xenbus_dev_request_and_reply(struct xsd_sockmsg *msg, void *par)
{
- void *ret;
- enum xsd_sockmsg_type type = msg->type;
- int err;
-
- if (type == XS_TRANSACTION_START)
- transaction_start();
+ struct xb_req_data *req;
+ struct kvec *vec;
- mutex_lock(&xs_state.request_mutex);
+ req = kmalloc(sizeof(*req) + sizeof(*vec), GFP_KERNEL);
+ if (!req)
+ return -ENOMEM;
- err = xb_write(msg, sizeof(*msg) + msg->len);
- if (err) {
- msg->type = XS_ERROR;
- ret = ERR_PTR(err);
- } else
- ret = read_reply(&msg->type, &msg->len);
+ vec = (struct kvec *)(req + 1);
+ vec->iov_len = msg->len;
+ vec->iov_base = msg + 1;
- mutex_unlock(&xs_state.request_mutex);
+ req->vec = vec;
+ req->num_vecs = 1;
+ req->cb = xenbus_dev_queue_reply;
+ req->par = par;
- if ((msg->type == XS_TRANSACTION_END) ||
- ((type == XS_TRANSACTION_START) && (msg->type == XS_ERROR)))
- transaction_end();
+ xs_send(req, msg);
- return ret;
+ return 0;
}
EXPORT_SYMBOL(xenbus_dev_request_and_reply);
unsigned int num_vecs,
unsigned int *len)
{
+ struct xb_req_data *req;
struct xsd_sockmsg msg;
void *ret = NULL;
unsigned int i;
int err;
+ req = kmalloc(sizeof(*req), GFP_NOIO | __GFP_HIGH);
+ if (!req)
+ return ERR_PTR(-ENOMEM);
+
+ req->vec = iovec;
+ req->num_vecs = num_vecs;
+ req->cb = xs_wake_up;
+
msg.tx_id = t.id;
- msg.req_id = 0;
msg.type = type;
msg.len = 0;
for (i = 0; i < num_vecs; i++)
msg.len += iovec[i].iov_len;
- mutex_lock(&xs_state.request_mutex);
-
- err = xb_write(&msg, sizeof(msg));
- if (err) {
- mutex_unlock(&xs_state.request_mutex);
- return ERR_PTR(err);
- }
-
- for (i = 0; i < num_vecs; i++) {
- err = xb_write(iovec[i].iov_base, iovec[i].iov_len);
- if (err) {
- mutex_unlock(&xs_state.request_mutex);
- return ERR_PTR(err);
- }
- }
-
- ret = read_reply(&msg.type, len);
+ xs_send(req, &msg);
- mutex_unlock(&xs_state.request_mutex);
+ ret = xs_wait_for_reply(req, &msg);
+ if (len)
+ *len = msg.len;
if (IS_ERR(ret))
return ret;
{
char *id_str;
- transaction_start();
-
id_str = xs_single(XBT_NIL, XS_TRANSACTION_START, "", NULL);
- if (IS_ERR(id_str)) {
- transaction_end();
+ if (IS_ERR(id_str))
return PTR_ERR(id_str);
- }
t->id = simple_strtoul(id_str, NULL, 0);
kfree(id_str);
int xenbus_transaction_end(struct xenbus_transaction t, int abort)
{
char abortstr[2];
- int err;
if (abort)
strcpy(abortstr, "F");
else
strcpy(abortstr, "T");
- err = xs_error(xs_single(t, XS_TRANSACTION_END, abortstr, NULL));
-
- transaction_end();
-
- return err;
+ return xs_error(xs_single(t, XS_TRANSACTION_END, abortstr, NULL));
}
EXPORT_SYMBOL_GPL(xenbus_transaction_end);
return NULL;
}
+
+int xs_watch_msg(struct xs_watch_event *event)
+{
+ if (count_strings(event->body, event->len) != 2) {
+ kfree(event);
+ return -EINVAL;
+ }
+ event->path = (const char *)event->body;
+ event->token = (const char *)strchr(event->body, '\0') + 1;
+
+ spin_lock(&watches_lock);
+ event->handle = find_watch(event->token);
+ if (event->handle != NULL) {
+ spin_lock(&watch_events_lock);
+ list_add_tail(&event->list, &watch_events);
+ wake_up(&watch_events_waitq);
+ spin_unlock(&watch_events_lock);
+ } else
+ kfree(event);
+ spin_unlock(&watches_lock);
+
+ return 0;
+}
+
/*
* Certain older XenBus toolstack cannot handle reading values that are
* not populated. Some Xen 3.4 installation are incapable of doing this
sprintf(token, "%lX", (long)watch);
- down_read(&xs_state.watch_mutex);
+ down_read(&xs_watch_rwsem);
spin_lock(&watches_lock);
BUG_ON(find_watch(token));
spin_unlock(&watches_lock);
}
- up_read(&xs_state.watch_mutex);
+ up_read(&xs_watch_rwsem);
return err;
}
void unregister_xenbus_watch(struct xenbus_watch *watch)
{
- struct xs_stored_msg *msg, *tmp;
+ struct xs_watch_event *event, *tmp;
char token[sizeof(watch) * 2 + 1];
int err;
sprintf(token, "%lX", (long)watch);
- down_read(&xs_state.watch_mutex);
+ down_read(&xs_watch_rwsem);
spin_lock(&watches_lock);
BUG_ON(!find_watch(token));
if (err)
pr_warn("Failed to release watch %s: %i\n", watch->node, err);
- up_read(&xs_state.watch_mutex);
+ up_read(&xs_watch_rwsem);
/* Make sure there are no callbacks running currently (unless
its us) */
/* 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)
+ list_for_each_entry_safe(event, tmp, &watch_events, list) {
+ if (event->handle != watch)
continue;
- list_del(&msg->list);
- kfree(msg->u.watch.vec);
- kfree(msg);
+ list_del(&event->list);
+ kfree(event);
}
spin_unlock(&watch_events_lock);
void xs_suspend(void)
{
- transaction_suspend();
- down_write(&xs_state.watch_mutex);
- mutex_lock(&xs_state.request_mutex);
- mutex_lock(&xs_state.response_mutex);
+ xs_suspend_enter();
+
+ down_write(&xs_watch_rwsem);
+ mutex_lock(&xs_response_mutex);
}
void xs_resume(void)
xb_init_comms();
- mutex_unlock(&xs_state.response_mutex);
- mutex_unlock(&xs_state.request_mutex);
- transaction_resume();
+ mutex_unlock(&xs_response_mutex);
+
+ xs_suspend_exit();
- /* No need for watches_lock: the watch_mutex is sufficient. */
+ /* No need for watches_lock: the xs_watch_rwsem is sufficient. */
list_for_each_entry(watch, &watches, list) {
sprintf(token, "%lX", (long)watch);
xs_watch(watch->node, token);
}
- up_write(&xs_state.watch_mutex);
+ up_write(&xs_watch_rwsem);
}
void xs_suspend_cancel(void)
{
- mutex_unlock(&xs_state.response_mutex);
- mutex_unlock(&xs_state.request_mutex);
- up_write(&xs_state.watch_mutex);
- mutex_unlock(&xs_state.transaction_mutex);
+ mutex_unlock(&xs_response_mutex);
+ up_write(&xs_watch_rwsem);
+
+ xs_suspend_exit();
}
static int xenwatch_thread(void *unused)
{
struct list_head *ent;
- struct xs_stored_msg *msg;
+ struct xs_watch_event *event;
for (;;) {
wait_event_interruptible(watch_events_waitq,
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);
+ event = list_entry(ent, struct xs_watch_event, list);
+ event->handle->callback(event->handle, event->path,
+ event->token);
+ kfree(event);
}
mutex_unlock(&xenwatch_mutex);
return 0;
}
-static int process_msg(void)
+/*
+ * Wake up all threads waiting for a xenstore reply. In case of shutdown all
+ * pending replies will be marked as "aborted" in order to let the waiters
+ * return in spite of xenstore possibly no longer being able to reply. This
+ * will avoid blocking shutdown by a thread waiting for xenstore but being
+ * necessary for shutdown processing to proceed.
+ */
+static int xs_reboot_notify(struct notifier_block *nb,
+ unsigned long code, void *unused)
{
- struct xs_stored_msg *msg;
- char *body;
- int err;
-
- /*
- * We must disallow save/restore while reading a xenstore message.
- * A partial read across s/r leaves us out of sync with xenstored.
- */
- for (;;) {
- err = xb_wait_for_data_to_read();
- if (err)
- return err;
- mutex_lock(&xs_state.response_mutex);
- if (xb_data_to_read())
- break;
- /* We raced with save/restore: pending data 'disappeared'. */
- mutex_unlock(&xs_state.response_mutex);
- }
-
-
- msg = kmalloc(sizeof(*msg), GFP_NOIO | __GFP_HIGH);
- if (msg == NULL) {
- err = -ENOMEM;
- goto out;
- }
-
- err = xb_read(&msg->hdr, sizeof(msg->hdr));
- if (err) {
- kfree(msg);
- goto out;
- }
-
- if (msg->hdr.len > XENSTORE_PAYLOAD_MAX) {
- kfree(msg);
- err = -EINVAL;
- goto out;
- }
-
- body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH);
- if (body == NULL) {
- kfree(msg);
- err = -ENOMEM;
- goto out;
- }
-
- err = xb_read(body, msg->hdr.len);
- if (err) {
- kfree(body);
- kfree(msg);
- goto out;
- }
- body[msg->hdr.len] = '\0';
-
- if (msg->hdr.type == XS_WATCH_EVENT) {
- msg->u.watch.vec = split(body, msg->hdr.len,
- &msg->u.watch.vec_size);
- if (IS_ERR(msg->u.watch.vec)) {
- err = PTR_ERR(msg->u.watch.vec);
- kfree(msg);
- goto out;
- }
-
- spin_lock(&watches_lock);
- msg->u.watch.handle = find_watch(
- msg->u.watch.vec[XS_WATCH_TOKEN]);
- if (msg->u.watch.handle != NULL) {
- 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);
- }
- spin_unlock(&watches_lock);
- } else {
- msg->u.reply.body = body;
- spin_lock(&xs_state.reply_lock);
- list_add_tail(&msg->list, &xs_state.reply_list);
- spin_unlock(&xs_state.reply_lock);
- wake_up(&xs_state.reply_waitq);
- }
+ struct xb_req_data *req;
- out:
- mutex_unlock(&xs_state.response_mutex);
- return err;
+ mutex_lock(&xb_write_mutex);
+ list_for_each_entry(req, &xs_reply_list, list)
+ wake_up(&req->wq);
+ list_for_each_entry(req, &xb_write_list, list)
+ wake_up(&req->wq);
+ mutex_unlock(&xb_write_mutex);
+ return NOTIFY_DONE;
}
-static int xenbus_thread(void *unused)
-{
- int err;
-
- for (;;) {
- err = process_msg();
- if (err)
- pr_warn("error %d while reading message\n", err);
- if (kthread_should_stop())
- break;
- }
-
- return 0;
-}
+static struct notifier_block xs_reboot_nb = {
+ .notifier_call = xs_reboot_notify,
+};
int xs_init(void)
{
int err;
struct task_struct *task;
- INIT_LIST_HEAD(&xs_state.reply_list);
- spin_lock_init(&xs_state.reply_lock);
- init_waitqueue_head(&xs_state.reply_waitq);
-
- mutex_init(&xs_state.request_mutex);
- mutex_init(&xs_state.response_mutex);
- mutex_init(&xs_state.transaction_mutex);
- init_rwsem(&xs_state.watch_mutex);
- atomic_set(&xs_state.transaction_count, 0);
- init_waitqueue_head(&xs_state.transaction_wq);
+ register_reboot_notifier(&xs_reboot_nb);
/* Initialize the shared memory rings to talk to xenstored */
err = xb_init_comms();
return PTR_ERR(task);
xenwatch_pid = task->pid;
- task = kthread_run(xenbus_thread, NULL, "xenbus");
- if (IS_ERR(task))
- return PTR_ERR(task);
-
/* shutdown watches for kexec boot */
xs_reset_watches();
projects / karo-tx-linux.git / blobdiff