New requests and responses are never sent if a request was sent and the
response for it hasn't been received yet. As a result, if both end
points send requests at the same time, a deadlock could occur. This
could happen, for instance, if the client sends a read request and the
server sends an indication before responding to the read request.
Fix this by introducing an additional queue for responses. Responses may
be sent while there's still a pending request/indication.
---
attrib/gattrib.c | 86 +++++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 69 insertions(+), 17 deletions(-)
diff --git a/attrib/gattrib.c b/attrib/gattrib.c
index 769be36..769d746 100644
--- a/attrib/gattrib.c
+++ b/attrib/gattrib.c
@@ -47,6 +47,7 @@ struct _GAttrib {
guint write_watch;
guint timeout_watch;
GQueue *queue;
+ GQueue *response_queue;
GSList *events;
guint next_cmd_id;
guint next_evt_id;
@@ -175,9 +176,13 @@ static void attrib_destroy(GAttrib *attrib)
while ((c = g_queue_pop_head(attrib->queue)))
command_destroy(c);
+ while ((c = g_queue_pop_head(attrib->response_queue)))
+ command_destroy(c);
g_queue_free(attrib->queue);
attrib->queue = NULL;
+ g_queue_free(attrib->response_queue);
+ attrib->response_queue = NULL;
for (l = attrib->events; l; l = l->next)
event_destroy(l->data);
@@ -259,21 +264,34 @@ static gboolean can_write_data(GIOChannel *io, GIOCondition cond,
GError *gerr = NULL;
gsize len;
GIOStatus iostat;
+ GQueue *queue;
if (cond & (G_IO_HUP | G_IO_ERR | G_IO_NVAL))
return FALSE;
- cmd = g_queue_peek_head(attrib->queue);
+ queue = attrib->response_queue;
+ cmd = g_queue_peek_head(queue);
+ if (cmd == NULL) {
+ queue = attrib->queue;
+ cmd = g_queue_peek_head(queue);
+ }
if (cmd == NULL)
return FALSE;
+ /*
+ * Verify that we didn't already send this command. This can only
+ * happen with elementes from attrib->queue.
+ */
+ if (cmd->sent)
+ return FALSE;
+
iostat = g_io_channel_write_chars(io, (gchar *) cmd->pdu, cmd->len,
&len, &gerr);
if (iostat != G_IO_STATUS_NORMAL)
return FALSE;
if (cmd->expected == 0) {
- g_queue_pop_head(attrib->queue);
+ g_queue_pop_head(queue);
command_destroy(cmd);
return TRUE;
@@ -315,7 +333,7 @@ static gboolean received_data(GIOChannel *io, GIOCondition cond, gpointer data)
uint8_t buf[512], status;
gsize len;
GIOStatus iostat;
- gboolean qempty;
+ gboolean qempty, respqempty;
if (attrib->timeout_watch > 0) {
g_source_remove(attrib->timeout_watch);
@@ -369,6 +387,8 @@ static gboolean received_data(GIOChannel *io, GIOCondition cond, gpointer data)
done:
qempty = attrib->queue == NULL || g_queue_is_empty(attrib->queue);
+ respqempty = attrib->response_queue == NULL ||
+ g_queue_is_empty(attrib->response_queue);
if (cmd) {
if (cmd->func)
@@ -377,7 +397,7 @@ done:
command_destroy(cmd);
}
- if (!qempty)
+ if (!qempty || !respqempty)
wake_up_sender(attrib);
return TRUE;
@@ -397,6 +417,7 @@ GAttrib *g_attrib_new(GIOChannel *io)
attrib->io = g_io_channel_ref(io);
attrib->queue = g_queue_new();
+ attrib->response_queue = g_queue_new();
attrib->read_watch = g_io_add_watch(attrib->io,
G_IO_IN | G_IO_HUP | G_IO_ERR | G_IO_NVAL,
@@ -421,6 +442,7 @@ guint g_attrib_send(GAttrib *attrib, guint id, guint8 opcode,
gpointer user_data, GDestroyNotify notify)
{
struct command *c;
+ GQueue *queue;
c = g_try_new0(struct command, 1);
if (c == NULL)
@@ -435,15 +457,25 @@ guint g_attrib_send(GAttrib *attrib, guint id, guint8 opcode,
c->user_data = user_data;
c->notify = notify;
+ if (is_response(opcode))
+ queue = attrib->response_queue;
+ else
+ queue = attrib->queue;
+
if (id) {
c->id = id;
- g_queue_push_head(attrib->queue, c);
+ g_queue_push_head(queue, c);
} else {
c->id = ++attrib->next_cmd_id;
- g_queue_push_tail(attrib->queue, c);
+ g_queue_push_tail(queue, c);
}
- if (g_queue_get_length(attrib->queue) == 1)
+ /*
+ * If a command was added to the queue and it was empty before, wake up
+ * the sender. If the sender was already woken up by the second queue,
+ * wake_up_sender will just return.
+ */
+ if (g_queue_get_length(queue) == 1)
wake_up_sender(attrib);
return c->id;
@@ -459,38 +491,49 @@ static gint command_cmp_by_id(gconstpointer a, gconstpointer b)
gboolean g_attrib_cancel(GAttrib *attrib, guint id)
{
- GList *l;
+ GList *l = NULL;
struct command *cmd;
+ GQueue *queue;
- if (attrib == NULL || attrib->queue == NULL)
+ if (attrib == NULL)
return FALSE;
- l = g_queue_find_custom(attrib->queue, GUINT_TO_POINTER(id),
- command_cmp_by_id);
+ queue = attrib->queue;
+ if (queue)
+ l = g_queue_find_custom(queue, GUINT_TO_POINTER(id),
+ command_cmp_by_id);
+ if (l == NULL) {
+ queue = attrib->response_queue;
+ if (!queue)
+ return FALSE;
+ l = g_queue_find_custom(queue, GUINT_TO_POINTER(id),
+ command_cmp_by_id);
+ }
+
if (l == NULL)
return FALSE;
cmd = l->data;
- if (cmd == g_queue_peek_head(attrib->queue) && cmd->sent)
+ if (cmd == g_queue_peek_head(queue) && cmd->sent)
cmd->func = NULL;
else {
- g_queue_remove(attrib->queue, cmd);
+ g_queue_remove(queue, cmd);
command_destroy(cmd);
}
return TRUE;
}
-gboolean g_attrib_cancel_all(GAttrib *attrib)
+static gboolean g_attrib_cancel_all_per_queue(GQueue *queue)
{
struct command *c, *head = NULL;
gboolean first = TRUE;
- if (attrib == NULL || attrib->queue == NULL)
+ if (queue == NULL)
return FALSE;
- while ((c = g_queue_pop_head(attrib->queue))) {
+ while ((c = g_queue_pop_head(queue))) {
if (first && c->sent) {
/* If the command was sent ignore its callback ... */
c->func = NULL;
@@ -504,12 +547,21 @@ gboolean g_attrib_cancel_all(GAttrib *attrib)
if (head) {
/* ... and put it back in the queue */
- g_queue_push_head(attrib->queue, head);
+ g_queue_push_head(queue, head);
}
return TRUE;
}
+gboolean g_attrib_cancel_all(GAttrib *attrib)
+{
+ if (attrib == NULL)
+ return FALSE;
+
+ return g_attrib_cancel_all_per_queue(attrib->queue) &&
+ g_attrib_cancel_all_per_queue(attrib->response_queue);
+}
+
gboolean g_attrib_set_debug(GAttrib *attrib,
GAttribDebugFunc func, gpointer user_data)
{
--
1.7.7.6
--
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