Changes between Initial Version and Version 1 of MutekS

Timestamp:

Jul 31, 2006, 12:24:32 PM (19 years ago)

Author:

Nicolas Pouillon

Comment:

Little explaination of MutekS's sched

MutekS

@@ +1 @@
+= MutekS =
+
+MutekS is the canonical Operating System for embedded software.
+It only implements the few system calls used by DSX.
+
+[source:trunk/dsx/lib/muteks]
+
+== Available services ==
+
+ * Locks (spin locks)
+ * Synchronization barriers
+ * Mwmr fifos
+
+== Implementation notes ==
+
+Scheduler is very basic. It's build on the simple assertion scheduling decisions can be simplified to comparing a address value vith a fixed value. 
+Six calls are available to set a thread waiting:
+{{{
+sched_wait_eq
+sched_wait_ne
+sched_wait_gt
+sched_wait_lt
+sched_wait_ge
+sched_wait_lt
+}}}
+
+Thus locking becomes:
+{{{
+/*
+ * Waits until a 0 is read at the lock address. This is only true when you get the lock
+ */
+sched_wait_eq( &lock, 0 );
+}}}
+
+Waiting on mwmr becomes:
+{{{
+/*
+ * Read on fifo, need data in it
+ * Wait on status before getting the lock, we are read-only and we'll refresh the value once the lock gotten
+ */
+...
+try_again:
+  sched_wait_ge( &(mwmr->status), needed );
+  dsx_lock_lock( mwmr->lock );
+  if ( mwmr->status < needed ) {
+    // Someone probably got the lock in between and emptied the fifo
+    dsx_lock_unlock( mwmr->lock, needed );
+    goto try_again;
+  }
+...
+}}}
+
+And so on...