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 | 107 ++++++++++++++++++++++++++++++++++++++++++------------
1 files changed, 83 insertions(+), 24 deletions(-)
diff --git a/attrib/gattrib.c b/attrib/gattrib.c
index 769be36..71c94d8 100644
--- a/attrib/gattrib.c
+++ b/attrib/gattrib.c
@@ -46,7 +46,8 @@ struct _GAttrib {
guint read_watch;
guint write_watch;
guint timeout_watch;
- GQueue *queue;
+ GQueue *requests;
+ GQueue *responses;
GSList *events;
guint next_cmd_id;
guint next_evt_id;
@@ -173,11 +174,17 @@ static void attrib_destroy(GAttrib *attrib)
GSList *l;
struct command *c;
- while ((c = g_queue_pop_head(attrib->queue)))
+ while ((c = g_queue_pop_head(attrib->requests)))
+ command_destroy(c);
+
+ while ((c = g_queue_pop_head(attrib->responses)))
command_destroy(c);
- g_queue_free(attrib->queue);
- attrib->queue = NULL;
+ g_queue_free(attrib->requests);
+ attrib->requests = NULL;
+
+ g_queue_free(attrib->responses);
+ attrib->responses = NULL;
for (l = attrib->events; l; l = l->next)
event_destroy(l->data);
@@ -259,21 +266,34 @@ 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->responses;
+ cmd = g_queue_peek_head(queue);
+ if (cmd == NULL) {
+ queue = attrib->requests;
+ 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->requests.
+ */
+ 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 +335,7 @@ static gboolean received_data(GIOChannel *io, GIOCondition cond, gpointer data)
uint8_t buf[512], status;
gsize len;
GIOStatus iostat;
- gboolean qempty;
+ gboolean norequests, noresponses;
if (attrib->timeout_watch > 0) {
g_source_remove(attrib->timeout_watch);
@@ -349,7 +369,7 @@ static gboolean received_data(GIOChannel *io, GIOCondition cond, gpointer data)
if (is_response(buf[0]) == FALSE)
return TRUE;
- cmd = g_queue_pop_head(attrib->queue);
+ cmd = g_queue_pop_head(attrib->requests);
if (cmd == NULL) {
/* Keep the watch if we have events to report */
return attrib->events != NULL;
@@ -368,7 +388,10 @@ static gboolean received_data(GIOChannel *io, GIOCondition cond, gpointer data)
status = 0;
done:
- qempty = attrib->queue == NULL || g_queue_is_empty(attrib->queue);
+ norequests = attrib->requests == NULL ||
+ g_queue_is_empty(attrib->requests);
+ noresponses = attrib->responses == NULL ||
+ g_queue_is_empty(attrib->responses);
if (cmd) {
if (cmd->func)
@@ -377,7 +400,7 @@ done:
command_destroy(cmd);
}
- if (!qempty)
+ if (!norequests || !noresponses)
wake_up_sender(attrib);
return TRUE;
@@ -396,7 +419,8 @@ GAttrib *g_attrib_new(GIOChannel *io)
return NULL;
attrib->io = g_io_channel_ref(io);
- attrib->queue = g_queue_new();
+ attrib->requests = g_queue_new();
+ attrib->responses = 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 +445,7 @@ 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 +460,29 @@ guint g_attrib_send(GAttrib *attrib, guint id, guint8 opcode,
c->user_data = user_data;
c->notify = notify;
+ if (is_response(opcode))
+ queue = attrib->responses;
+ else
+ queue = attrib->requests;
+
if (id) {
c->id = id;
- g_queue_push_head(attrib->queue, c);
+ if (!is_response(opcode))
+ g_queue_push_head(queue, c);
+ else
+ /* Don't re-order responses even if an ID is given */
+ g_queue_push_tail(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 +498,49 @@ 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->requests;
+ if (queue)
+ l = g_queue_find_custom(queue, GUINT_TO_POINTER(id),
+ command_cmp_by_id);
+ if (l == NULL) {
+ queue = attrib->responses;
+ 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 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 +554,21 @@ 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 cancel_all_per_queue(attrib->requests) &&
+ cancel_all_per_queue(attrib->responses);
+}
+
gboolean g_attrib_set_debug(GAttrib *attrib,
GAttribDebugFunc func, gpointer user_data)
{
--
1.7.7.6
--
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