[Spice-devel] [PATCH spice-server v2 01/12] dispatcher: Allows to manage messages without registering them
Jonathon Jongsma
jjongsma at redhat.com
Thu Mar 28 15:23:35 UTC 2019
On Tue, 2019-03-26 at 19:10 +0000, Frediano Ziglio wrote:
> The only way to add new message to Dispatcher was to register
> using a number. These numbers corresponded to array indexes.
> This is good if the list of messages is allocated statically
> and contiguously, on the contrary this method is not that
> flexible.
> Writing a header of 4 or 16 bytes using system call does not
> make much difference so pass all message information in the
> payload header.
> A new dispatcher_send_message_custom function allows to send
> a message passing all message information, including the
> pointer to the handler.
> This will allow for instance a Dispatcher associate to a given
> thread to be reused by different classes.
>
> Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> ---
> server/dispatcher.c | 77 +++++++++++++++++++++++++++++++----------
> ----
> server/dispatcher.h | 15 +++++++++
> 2 files changed, 68 insertions(+), 24 deletions(-)
>
> diff --git a/server/dispatcher.c b/server/dispatcher.c
> index 5f839ec4..ed4037aa 100644
> --- a/server/dispatcher.c
> +++ b/server/dispatcher.c
> @@ -38,10 +38,19 @@
> static void setup_dummy_signal_handler(void);
> #endif
>
> +#define DISPATCHER_CUSTOM_TYPE 0x7fffffffu
Can I suggest DISPATCHER_MESSAGE_TYPE_CUSTOM ?
> +
> +/* structure to store message header information.
> + * That structure is sent through a socketpair so it's optimized
> + * to be transfered via sockets.
> + * Is also packaged to not leave holes in both 32 and 64
> environments
> + * so memory instrumentation tools should not find uninitialised
> bytes.
> + */
> typedef struct DispatcherMessage {
> - size_t size;
> - bool ack;
> dispatcher_handle_message handler;
> + uint32_t size;
> + uint32_t type:31;
> + uint32_t ack:1;
> } DispatcherMessage;
>
> struct DispatcherPrivate {
> @@ -249,12 +258,11 @@ static int write_safe(int fd, uint8_t *buf,
> size_t size)
> static int dispatcher_handle_single_read(Dispatcher *dispatcher)
> {
> int ret;
> - uint32_t type;
> - DispatcherMessage *msg = NULL;
> - uint8_t *payload = dispatcher->priv->payload;
> + DispatcherMessage msg[1];
> + uint8_t *payload;
> uint32_t ack = ACK;
>
> - if ((ret = read_safe(dispatcher->priv->recv_fd, (uint8_t*)&type,
> sizeof(type), 0)) == -1) {
> + if ((ret = read_safe(dispatcher->priv->recv_fd, (uint8_t*)msg,
> sizeof(msg), 0)) == -1) {
> g_warning("error reading from dispatcher: %d", errno);
> return 0;
> }
> @@ -262,28 +270,28 @@ static int
> dispatcher_handle_single_read(Dispatcher *dispatcher)
> /* no message */
> return 0;
> }
> - if (type >= dispatcher->priv->max_message_type) {
> - spice_error("Invalid message type for this dispatcher: %u",
> type);
> - return 0;
> + if (G_UNLIKELY(msg->size > dispatcher->priv->payload_size)) {
> + dispatcher->priv->payload = g_realloc(dispatcher->priv-
> >payload, msg->size);
> + dispatcher->priv->payload_size = msg->size;
> }
> - msg = &dispatcher->priv->messages[type];
> + payload = dispatcher->priv->payload;
> if (read_safe(dispatcher->priv->recv_fd, payload, msg->size, 1)
> == -1) {
> g_warning("error reading from dispatcher: %d", errno);
> /* TODO: close socketpair? */
> return 0;
> }
> - if (dispatcher->priv->any_handler) {
> - dispatcher->priv->any_handler(dispatcher->priv->opaque,
> type, payload);
> + if (dispatcher->priv->any_handler && msg->type !=
> DISPATCHER_CUSTOM_TYPE) {
> + dispatcher->priv->any_handler(dispatcher->priv->opaque, msg-
> >type, payload);
> }
> if (msg->handler) {
> msg->handler(dispatcher->priv->opaque, payload);
> } else {
> - g_warning("error: no handler for message type %d", type);
> + g_warning("error: no handler for message type %d", msg-
> >type);
> }
> if (msg->ack) {
> if (write_safe(dispatcher->priv->recv_fd,
> (uint8_t*)&ack, sizeof(ack)) == -1) {
> - g_warning("error writing ack for message %d", type);
> + g_warning("error writing ack for message %d", msg-
> >type);
> /* TODO: close socketpair? */
> }
> }
> @@ -300,25 +308,22 @@ void dispatcher_handle_recv_read(Dispatcher
> *dispatcher)
> }
> }
>
> -void dispatcher_send_message(Dispatcher *dispatcher, uint32_t
> message_type,
> - void *payload)
> +static void
> +dispatcher_send_message_internal(Dispatcher *dispatcher, const
> DispatcherMessage*msg,
> + void *payload)
> {
> - DispatcherMessage *msg;
> uint32_t ack;
> int send_fd = dispatcher->priv->send_fd;
>
> - assert(dispatcher->priv->max_message_type > message_type);
> - assert(dispatcher->priv->messages[message_type].handler);
You've removed a bunch of asserts here, but do we want to assert (or at
least g_return_if_fail) if msg is NULL?
> - msg = &dispatcher->priv->messages[message_type];
> pthread_mutex_lock(&dispatcher->priv->lock);
> - if (write_safe(send_fd, (uint8_t*)&message_type,
> sizeof(message_type)) == -1) {
> + if (write_safe(send_fd, (uint8_t*)msg, sizeof(*msg)) == -1) {
> g_warning("error: failed to send message type for message
> %d",
Perhaps this warning message should be changed from "failed to send
message type" to "failed to send message header"?
> - message_type);
> + msg->type);
> goto unlock;
> }
> if (write_safe(send_fd, payload, msg->size) == -1) {
> g_warning("error: failed to send message body for message
> %d",
> - message_type);
> + msg->type);
> goto unlock;
> }
> if (msg->ack) {
> @@ -326,7 +331,7 @@ void dispatcher_send_message(Dispatcher
> *dispatcher, uint32_t message_type,
> g_warning("error: failed to read ack");
> } else if (ack != ACK) {
> g_warning("error: got wrong ack value in dispatcher "
> - "for message %d\n", message_type);
> + "for message %d\n", msg->type);
> /* TODO handling error? */
> }
> }
> @@ -334,6 +339,29 @@ unlock:
> pthread_mutex_unlock(&dispatcher->priv->lock);
> }
>
> +void dispatcher_send_message(Dispatcher *dispatcher, uint32_t
> message_type,
> + void *payload)
> +{
> + DispatcherMessage *msg;
> +
> + assert(dispatcher->priv->max_message_type > message_type);
> + assert(dispatcher->priv->messages[message_type].handler);
> + msg = &dispatcher->priv->messages[message_type];
> + dispatcher_send_message_internal(dispatcher, msg, payload);
> +}
> +
> +void dispatcher_send_message_custom(Dispatcher *dispatcher,
> dispatcher_handle_message handler,
> + void *payload, uint32_t
> payload_size, bool ack)
> +{
> + DispatcherMessage msg = {
> + .handler = handler,
> + .size = payload_size,
> + .type = DISPATCHER_CUSTOM_TYPE,
> + .ack = ack,
> + };
> + dispatcher_send_message_internal(dispatcher, &msg, payload);
> +}
> +
> void dispatcher_register_handler(Dispatcher *dispatcher, uint32_t
> message_type,
> dispatcher_handle_message handler,
> size_t size, bool ack)
> @@ -345,6 +373,7 @@ void dispatcher_register_handler(Dispatcher
> *dispatcher, uint32_t message_type,
> msg = &dispatcher->priv->messages[message_type];
> msg->handler = handler;
> msg->size = size;
> + msg->type = message_type;
> msg->ack = ack;
> if (msg->size > dispatcher->priv->payload_size) {
> dispatcher->priv->payload = g_realloc(dispatcher->priv-
> >payload, msg->size);
> diff --git a/server/dispatcher.h b/server/dispatcher.h
> index bb968e56..a7aaebed 100644
> --- a/server/dispatcher.h
> +++ b/server/dispatcher.h
> @@ -99,6 +99,21 @@ typedef void (*dispatcher_handle_any_message)(void
> *opaque,
> void dispatcher_send_message(Dispatcher *dispatcher, uint32_t
> message_type,
> void *payload);
>
> +/* dispatcher_send_message_custom
> + *
> + * Sends a message to the receiving thread.
> + *
> + * If the sent message is a message type requires an ACK, this
> function will
> + * block until it receives an ACK from the receiving thread.
The comment above is a little bit confusing because in this case the
message type doesn't determine whether an ACK is required. The @ack
argument determines whether an ACK is required. Maybe remove the phrase
"is a message type ". So it becomes:
"If the sent message requires an ACK, this function..."
> + *
> + * @handler: callback to handle message
> + * @payload: payload
> + * @payload_size: size of payload
> + * @ack: acknowledge required. Make message synchronous
> + */
> +void dispatcher_send_message_custom(Dispatcher *dispatcher,
> dispatcher_handle_message handler,
> + void *payload, uint32_t
> payload_size, bool ack);
> +
> /* dispatcher_register_handler
> *
> * This function registers a message type with the dispatcher, and
> registers
with minor comments above:
Acked-by: Jonathon Jongsma <jjongsma at redhat.com>
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