fix background scheduler with multiple tasks

[lttv.git] / ltt / branches / poly / lttv / modules / gui / lttvwindow / lttvwindow / lttvwindowtraces.h

diff --git a/ltt/branches/poly/lttv/modules/gui/lttvwindow/lttvwindow/lttvwindowtraces.h b/ltt/branches/poly/lttv/modules/gui/lttvwindow/lttvwindow/lttvwindowtraces.h
index 20ea0c43f599279495224963cc8e655c6f0ae7d8..fffb3025cf29558b0299a32efdd700ac781679c8 100644 (file)
--- a/ltt/branches/poly/lttv/modules/gui/lttvwindow/lttvwindow/lttvwindowtraces.h
+++ b/ltt/branches/poly/lttv/modules/gui/lttvwindow/lttvwindow/lttvwindowtraces.h
@@ -18,6 +18,53 @@
 
 /* This file is the API used to launch any background computation on a trace */
 
+/* lttvwindowtraces
+ *
+ * This API consists in two main parts. The first one is for the background
+ * computation provider and the second is for the viewer which needs this
+ * information.
+ *
+ * A computation provider, i.e. a statistics computation module or a state
+ * computation module, have two things in common : they append data to a trace
+ * in an extensible container (LttvAttributes). This extended information, once
+ * computed, can be kept all along with the trace and does not need to be
+ * recomputed : a computation done on a trace must result in a identical result
+ * each time it is done.
+ *
+ * This API provides functions for computation provider to register their
+ * computation functions (or computation functions insertion and removal
+ * functions). Once the computation provider is registered with its module name,
+ * extended computation for a trace can be requested by any viewer by specifying
+ * the module name, as we will describe in a moment.
+ *
+ * A viewer which needs extended information about a trace must ask for it to be
+ * computed by doing a background computation request. It may also ask to be
+ * notified of the completion of its request by doing a notify request.
+ *
+ * Before asking for the computation, it must check for its readiness. If it is
+ * ready, the information has already been computed, so it is ready to use. If
+ * the information is not ready, in must check whether or not the processing of
+ * this task is in progress. If it is, it must not do any background computation
+ * request. It must only do a background notification request of the current
+ * processing to be informed of its completion. If the information is not ready
+ * and not being processed, then the viewer may do a background computation
+ * request and add a notify request to the notify queue.
+ *
+ * When a context takes control of a trace, it must lock the trace. This is a
+ * way of ensuring that not conflict will occur between two traceset contexts
+ * and shared traces. It will generate an error if a context try to get a lock
+ * on a trace what is not unlocked. Upon every trace locking,
+ * lttv_process_traceset_synchronize_tracefiles should be used to resynchronize
+ * the traces with the trace context information.
+ *
+ * The usefulness of the lock in this framework can be questionable in a
+ * single threaded environment, but can be great in the eventuality of
+ * multiple threads.
+ * 
+ */
+
+
+
 #ifndef LTTVWINDOWTRACES_H
 #define LTTVWINDOWTRACES_H
 
@@ -47,7 +94,8 @@ extern LttvTraceInfo LTTV_TRACES,
               LTTV_HOOK_ADDER,
               LTTV_HOOK_REMOVER,
               LTTV_IN_PROGRESS,
-              LTTV_READY;
+              LTTV_READY,
+              LTTV_LOCK;
               
 
 
@@ -231,4 +279,30 @@ void lttvwindowtraces_unregister_computation_hooks
 void lttvwindowtraces_unregister_requests(LttvAttributeName module_name);
 
 
+/**
+ * Lock a trace so no other instance can use it.
+ *
+ * @param trace The trace to lock.
+ * @return 0 on success, -1 if cannot get lock.
+ */
+gint lttvwindowtraces_lock(LttvTrace *trace);
+
+
+/**
+ * Unlock a trace.
+ *
+ * @param trace The trace to unlock.
+ * @return 0 on success, -1 if cannot unlock (not locked ?).
+ */
+gint lttvwindowtraces_unlock(LttvTrace *trace);
+
+/**
+ * Verify if a trace is locked.
+ *
+ * @param trace The trace to verify.
+ * @return TRUE if locked, FALSE is unlocked.
+ */
+gint lttvwindowtraces_get_lock_state(LttvTrace *trace);
+
+
 #endif //LTTVWINDOWTRACES_H