diff options
Diffstat (limited to 'drivers/xen')
| -rw-r--r-- | drivers/xen/xenbus/xenbus_xs.c | 57 | ||||
| -rw-r--r-- | drivers/xen/xenfs/xenbus.c | 3 |
2 files changed, 50 insertions, 10 deletions
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c index 7b547f53f65e..5534690075af 100644 --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -76,6 +76,14 @@ struct xs_handle { /* * 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. */ @@ -85,7 +93,9 @@ struct xs_handle { struct mutex response_mutex; /* Protect transactions against save/restore. */ - struct rw_semaphore transaction_mutex; + 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; @@ -157,6 +167,31 @@ static void *read_reply(enum xsd_sockmsg_type *type, unsigned int *len) return body; } +static void transaction_start(void) +{ + mutex_lock(&xs_state.transaction_mutex); + atomic_inc(&xs_state.transaction_count); + mutex_unlock(&xs_state.transaction_mutex); +} + +static void transaction_end(void) +{ + if (atomic_dec_and_test(&xs_state.transaction_count)) + wake_up(&xs_state.transaction_wq); +} + +static void transaction_suspend(void) +{ + mutex_lock(&xs_state.transaction_mutex); + wait_event(xs_state.transaction_wq, + atomic_read(&xs_state.transaction_count) == 0); +} + +static void transaction_resume(void) +{ + mutex_unlock(&xs_state.transaction_mutex); +} + void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg) { void *ret; @@ -164,7 +199,7 @@ void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg) int err; if (req_msg.type == XS_TRANSACTION_START) - down_read(&xs_state.transaction_mutex); + transaction_start(); mutex_lock(&xs_state.request_mutex); @@ -180,7 +215,7 @@ void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg) if ((msg->type == XS_TRANSACTION_END) || ((req_msg.type == XS_TRANSACTION_START) && (msg->type == XS_ERROR))) - up_read(&xs_state.transaction_mutex); + transaction_end(); return ret; } @@ -432,11 +467,11 @@ int xenbus_transaction_start(struct xenbus_transaction *t) { char *id_str; - down_read(&xs_state.transaction_mutex); + transaction_start(); id_str = xs_single(XBT_NIL, XS_TRANSACTION_START, "", NULL); if (IS_ERR(id_str)) { - up_read(&xs_state.transaction_mutex); + transaction_end(); return PTR_ERR(id_str); } @@ -461,7 +496,7 @@ int xenbus_transaction_end(struct xenbus_transaction t, int abort) err = xs_error(xs_single(t, XS_TRANSACTION_END, abortstr, NULL)); - up_read(&xs_state.transaction_mutex); + transaction_end(); return err; } @@ -662,7 +697,7 @@ EXPORT_SYMBOL_GPL(unregister_xenbus_watch); void xs_suspend(void) { - down_write(&xs_state.transaction_mutex); + transaction_suspend(); down_write(&xs_state.watch_mutex); mutex_lock(&xs_state.request_mutex); mutex_lock(&xs_state.response_mutex); @@ -677,7 +712,7 @@ void xs_resume(void) mutex_unlock(&xs_state.response_mutex); mutex_unlock(&xs_state.request_mutex); - up_write(&xs_state.transaction_mutex); + transaction_resume(); /* No need for watches_lock: the watch_mutex is sufficient. */ list_for_each_entry(watch, &watches, list) { @@ -693,7 +728,7 @@ void xs_suspend_cancel(void) mutex_unlock(&xs_state.response_mutex); mutex_unlock(&xs_state.request_mutex); up_write(&xs_state.watch_mutex); - up_write(&xs_state.transaction_mutex); + mutex_unlock(&xs_state.transaction_mutex); } static int xenwatch_thread(void *unused) @@ -843,8 +878,10 @@ int xs_init(void) mutex_init(&xs_state.request_mutex); mutex_init(&xs_state.response_mutex); - init_rwsem(&xs_state.transaction_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); /* Initialize the shared memory rings to talk to xenstored */ err = xb_init_comms(); diff --git a/drivers/xen/xenfs/xenbus.c b/drivers/xen/xenfs/xenbus.c index f28ece397361..3b39c3752e21 100644 --- a/drivers/xen/xenfs/xenbus.c +++ b/drivers/xen/xenfs/xenbus.c @@ -124,6 +124,9 @@ static ssize_t xenbus_file_read(struct file *filp, mutex_lock(&u->reply_mutex); while (list_empty(&u->read_buffers)) { mutex_unlock(&u->reply_mutex); + if (filp->f_flags & O_NONBLOCK) + return -EAGAIN; + ret = wait_event_interruptible(u->read_waitq, !list_empty(&u->read_buffers)); if (ret) |