Add some code to track when a link was last active and some code in create link and the lock

check to see if a link hasn't been active for a long time and if so remove it.
This should make deadlocks less of a problem.. before if a link held the lock and then
disappeared no one else would ever be able to lock again. If 8 clients connected and
didn't shutdown their link no more clients would be able to connect.

1 files changed, 50 insertions, 7 deletions

diff --git a/vxi11_server.c b/vxi11_server.c
index ed529f2..bf57547 100644
--- a/vxi11_server.c
+++ b/vxi11_server.c
@@ -44,12 +44,18 @@ static CLIENT* intclient = NULL;
 static bool intenabled = false;
 static gchar* inthandler = NULL;
 
+#define LINKLONGSINCEDEADTIMEOUT ((10 * 60) * 1000000) // ten minutes
 typedef struct {
 	int lid;
+	GTimeVal lastactivity;
 } ActiveLink;
 
 static ActiveLink* links[MAX_SESSIONS] = { NULL };
 
+static void touchlink(int lid) {
+	g_get_current_time(&(links[lid]->lastactivity));
+}
+
 static bool isValidLink(int linkid) {
 	if (linkid > MAX_SESSIONS - 1) {
 #ifdef DEBUG
@@ -60,8 +66,31 @@ static bool isValidLink(int linkid) {
 	return links[linkid] != NULL;
 }
 
+// test if a link has expired, this is to avoid dead locks
+static bool linkexpired(ActiveLink* link) {
+	GTimeVal cutoff;
+	g_get_current_time(&cutoff);
+	g_time_val_add(&cutoff, -LINKLONGSINCEDEADTIMEOUT);
+	if (link->lastactivity.tv_sec < cutoff.tv_sec) {
+#ifdef DEBUG
+		printf("Link %d is apparently dead, removing\n", link->lid);
+#endif
+		links[link->lid] = NULL;
+		g_free(link);
+		globals.Remote.vxi_connections--;
+		return true;
+	}
+	else
+		return false;
+}
+
 static bool isLocked() {
-	return globals.VxiLocks.locked_network_server != NO_SERVER_LOCKED;
+	if (globals.VxiLocks.locked_network_server == NO_SERVER_LOCKED)
+		return false;
+	else {
+		ActiveLink* link = links[globals.VxiLocks.locked_network_server];
+		return !(linkexpired(link));
+	}
 }
 
 static bool haveLock(int lid) {
@@ -133,6 +162,8 @@ create_link_1_svc(Create_LinkParms *argp, struct svc_req *rqstp) {
 		else {
 			int linkid;
 			for (linkid = 0; linkid < SIZEOFARRAY(links); linkid++) {
+				if (links[linkid] != NULL) // clean up any dead links
+					linkexpired(links[linkid]);
 				if (links[linkid] == NULL) {
 					links[linkid] = link;
 					break;
@@ -140,7 +171,7 @@ create_link_1_svc(Create_LinkParms *argp, struct svc_req *rqstp) {
 			}
 			g_assert(linkid != SIZEOFARRAY(links));
 			link->lid = linkid;
-
+			touchlink(linkid);
 			globals.Remote.vxi_connections++;
 #ifdef DEBUG
 			printf("created link %d, %d active links\n", linkid, globals.Remote.vxi_connections);
@@ -172,6 +203,7 @@ device_write_1_svc(Device_WriteParms *argp, struct svc_req *rqstp) {
 	else if (!waitforio(argp->io_timeout))
 		result.error = ERR_IOTIMEOUT;
 	else {
+		touchlink(argp->lid);
 #ifdef DEBUG
 		printf("got %s on link %d\n", argp->data.data_val, (int) argp->lid);
 #endif
@@ -203,6 +235,7 @@ device_read_1_svc(Device_ReadParms *argp, struct svc_req *rqstp) {
 		result.error = ERR_IOTIMEOUT;
 	}
 	else {
+		touchlink(argp->lid);
 		if (globals.Registers.pending_output_message != NULL) {
 			result.data.data_len = strlen(globals.Registers.pending_output_message) + 1;
 			result.data.data_val = globals.Registers.pending_output_message;
@@ -230,9 +263,10 @@ device_readstb_1_svc(Device_GenericParms *argp, struct svc_req *rqstp) {
 		result.error = ERR_INVALIDLINKINDENTIFIER;
 	else if (isLocked() && !haveLock(argp->lid) && !waitForLock(argp->flags, argp->lock_timeout))
 		result.error = ERR_DEVICELOCKEDBYANOTHERLINK;
-	else
+	else {
+		touchlink(argp->lid);
 		result.stb = GPIB_and_VXI_get_STB();
-
+	}
 	return &result;
 }
 
@@ -247,6 +281,7 @@ device_trigger_1_svc(Device_GenericParms *argp, struct svc_req *rqstp) {
 	else if (isLocked() && !haveLock(argp->lid) && !waitForLock(argp->flags, argp->lock_timeout))
 		result.error = ERR_DEVICELOCKEDBYANOTHERLINK;
 	else {
+		touchlink(argp->lid);
 		result.error = 0;
 	}
 	return &result;
@@ -263,6 +298,7 @@ device_clear_1_svc(Device_GenericParms *argp, struct svc_req *rqstp) {
 	else if (isLocked() && !haveLock(argp->lid) && !waitForLock(argp->flags, argp->lock_timeout))
 		result.error = ERR_DEVICELOCKEDBYANOTHERLINK;
 	else {
+		touchlink(argp->lid);
 		result.error = 0;
 	}
 	return &result;
@@ -281,8 +317,10 @@ device_remote_1_svc(Device_GenericParms *argp, struct svc_req *rqstp) {
 	else {
 		if (isLocked() && !haveLock(argp->lid))
 			result.error = ERR_DEVICELOCKEDBYANOTHERLINK;
-		else
+		else {
+			touchlink(argp->lid);
 			result.error = 0;
+		}
 	}
 	return &result;
 }
@@ -300,8 +338,10 @@ device_local_1_svc(Device_GenericParms *argp, struct svc_req *rqstp) {
 	else {
 		if (isLocked() && !haveLock(argp->lid))
 			result.error = ERR_DEVICELOCKEDBYANOTHERLINK;
-		else
+		else {
+			touchlink(argp->lid);
 			result.error = 0;
+		}
 	}
 	return &result;
 }
@@ -322,6 +362,7 @@ device_lock_1_svc(Device_LockParms *argp, struct svc_req *rqstp) {
 			}
 		}
 		else {
+			touchlink(argp->lid);
 			lock(argp->lid);
 			result.error = 0;
 		}
@@ -341,6 +382,7 @@ device_unlock_1_svc(Device_Link *argp, struct svc_req *rqstp) {
 		if (!isLocked(*argp) || !haveLock(*argp))
 			result.error = ERR_NOLOCKHELDBYTHISLINK;
 		else {
+			touchlink(*argp);
 			result.error = 0;
 			unlock();
 		}
@@ -366,6 +408,7 @@ device_enable_srq_1_svc(Device_EnableSrqParms *argp, struct svc_req *rqstp) {
 	if (!isValidLink(argp->lid))
 		result.error = ERR_INVALIDLINKINDENTIFIER;
 	else {
+		touchlink(argp->lid);
 		if (inthandler != NULL) {
 			g_free(inthandler);
 			inthandler = NULL;
@@ -395,6 +438,7 @@ device_docmd_1_svc(Device_DocmdParms *argp, struct svc_req *rqstp) {
 	else if (isLocked() && !haveLock(argp->lid) && !waitForLock(argp->flags, argp->lock_timeout))
 		result.error = ERR_DEVICELOCKEDBYANOTHERLINK;
 	else {
+		touchlink(argp->lid);
 		result.data_out.data_out_len = 0;
 		result.data_out.data_out_val = NULL;
 		result.error = ERR_OPERATIONNOTSUPPORTED;
@@ -412,7 +456,6 @@ destroy_link_1_svc(Device_Link *argp, struct svc_req *rqstp) {
 	if (!isValidLink(lid))
 		result.error = ERR_INVALIDLINKINDENTIFIER;
 	else {
-
 		if (haveLock(*argp)) {
 #ifdef DEBUG
 			printf("Disconnecting client was holding a lock, freeing it\n");