Add a comment about desirable but complex error recovery

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4957 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/mgt_shmem.c

@@ -25,6 +25,63 @@
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
+ *
+ *
+ * TODO:
+ *
+ * There is a risk that the child process might corrupt the VSM segment
+ * and we should capture that event and recover gracefully.
+ *
+ * A possible state diagram could be:
+ *
+ *	[manager start]
+ *		|
+ *		v
+ *      Open old VSM,
+ *	check pid 	--------> exit/fail (-n message)
+ *		|
+ *		+<----------------------+
+ *		|			^
+ *		v			|
+ *	Create new VSM			|
+ *		|			|
+ *		v			|
+ *	Init header			|
+ *	Alloc VSL			|
+ *	Alloc VSC:Main			|
+ *	Alloc Args etc.			|
+ *		|			|
+ *		+<--------------+	|
+ *		|		^	|
+ *		v		|	|
+ *	start worker		|	|
+ *		|		|	|
+ *		|		|	+<---- worker crash
+ *		v		|	^
+ *	Reset VSL ptr.		|	|
+ *	Reset VSC counters	|	|
+ *		|		|	|
+ *		+<------+	|	|
+ *		|	^	|	|
+ *		v	|	|	|
+ *	alloc dynamics	|	|	|
+ *	free dynamics	|	|	|
+ *		|	|	|	|
+ *		v	|	|	|
+ *		+------>+	|	|
+ *		|		|	|
+ *		v		|	|
+ *	stop worker		|	|
+ *		|		|	|
+ *		v		|	|
+ *	Check consist---------- | ----->+
+ *		|		|
+ *		v		|
+ *	Free dynamics		|
+ *		|		|
+ *		v		|
+ *		+-------------->+
+ *		
  */
 
 #include "config.h"