Xen devel - Jun 2006 - [RFC PATCH] Run the Mini-OS application in its own thread.

Some Xen developers have questioned why one would ever need to run a
Mini-OS application before thread scheduling is enabled.  I can see no
reason to do it.  If no one else can, I suggest each an application be
a thread function that is started in kernel.c.

The following patch to kernel.c sets up and runs the application in
its own thread.

Signed-of-by: John D. Ramsdell <ramsdell@mitre.org>

diff -ur oxen-unstable/extras/mini-os/kernel.c
xen-unstable/extras/mini-os/kernel.c
--- oxen-unstable/extras/mini-os/kernel.c	2006-06-02 01:03:40.000000000 -0400
+++ xen-unstable/extras/mini-os/kernel.c	2006-06-07 17:39:52.000000000 -0400
@@ -82,17 +82,6 @@
 }
 
 
-void test_xenbus(void);
-
-/* Do initialisation from a thread once the scheduler''s available */
-static void init_xs(void *ign)
-{
-    init_xenbus();
-
-    test_xenbus();
-}
-
-
 u8 xen_features[XENFEAT_NR_SUBMAPS * 32];
 
 void setup_xen_features(void)
@@ -111,11 +100,13 @@
     }
 }
 
+void test_xenbus(void);
+
 /* This should be overridden by the application we are linked against. */
-__attribute__((weak)) int app_main(start_info_t *si)
+__attribute__((weak)) void app_main(void *si)
 {
     printk("Dummy main: start_info=%p\n", si);
-    return 0;
+    test_xenbus();
 }
 
 /*
@@ -183,11 +174,11 @@
     /* Init scheduler. */
     init_sched();
  
-    /* Init XenBus from a separate thread */
-    create_thread("init_xs", init_xs, NULL);
+    /* Init XenBus */
+    init_xenbus();
 
-    /* Call (possibly overridden) app_main() */
-    app_main(&start_info);
+    /* Schedule the possibly overridden app_main() function */
+    create_thread("app_main", app_main, &start_info);
 
     /* Everything initialised, start idle thread */
     run_idle_thread();

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On 08 Jun 2006 07:20:26 -0400, John D. Ramsdell <ramsdell@mitre.org>
wrote:
> Some Xen developers have questioned why one would ever need to run a
> Mini-OS application before thread scheduling is enabled.  I can see no
> reason to do it.  If no one else can, I suggest each an application be
> a thread function that is started in kernel.c.
I can, when writing a boot-loader there is no need for multiple
threads, so I would like the option of not having to start (and clean
up after) any.

Perhaps the last part of start_kernel() could be moved to a weak
function, that people like me can override?

Regards,
Jacob

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"Jacob Gorm Hansen" <jacobg@diku.dk> writes:
> I can, when writing a boot-loader there is no need for multiple
> threads, so I would like the option of not having to start (and clean
> up after) any.
I see.
> Perhaps the last part of start_kernel() could be moved to a weak
> function, that people like me can override?
I suggest we simply just leave kernel.c the way it is, and my patch be
ignored. 

John

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