From 5f6c2bcf0d2f9c416134aba224d90a605f216818 Mon Sep 17 00:00:00 2001
From: Miguel <m.i@gmx.at>
Date: Fri, 28 Sep 2018 11:13:06 +0200
Subject: struggling with scheduler and userprog to view ppm files

---
 kernel/scheduler.c | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

(limited to 'kernel/scheduler.c')

diff --git a/kernel/scheduler.c b/kernel/scheduler.c
index 0c24f94..23ed7b2 100644
--- a/kernel/scheduler.c
+++ b/kernel/scheduler.c
@@ -120,8 +120,10 @@ static uint32_t scheduler_schedule(uint32_t idx)
 	if(task_list[cpu][idx].active && !task_list[cpu][idx].syscall)
 	{
             if(current_task[cpu]!=0)last_task[cpu]=current_task[cpu];
-
 	    current_task[cpu]=idx;
+            
+           // klog("%d idx %d",last_task[cpu],current_task[cpu]);
+
 	    install_tss(cpu,task_list[cpu][idx].esp0);
 	    x86_set_page_directory(task_list[cpu][idx].vmem);
 	    return task_list[cpu][idx].esp;
@@ -153,19 +155,36 @@ volatile uint32_t scheduler_run(uint32_t oldesp,uint32_t preference)
     else task_list[cpu][current_task[cpu]].esp=oldesp;
 
     uint32_t esp;
-    esp=scheduler_schedule(preference); // try preference
 
-    if(esp)return esp;
+    if(preference!=-1)
+    {
+        esp=scheduler_schedule(preference); // try preference
+        if(esp)return esp;
+
+        if(current_task[cpu]==0)// we have interrupted a task with ring1 work
+        {
+            esp=scheduler_schedule(last_task[cpu]); // try preference
+            if(esp)return esp;
+        }
+    }
+    else
+    {
+        //klog("preempt %d", last_task[cpu]);
+    }
 
     for(int i=0;i<MAX_TASKS;i++)
     {
 	int idx=(last_task[cpu]+1+i)%MAX_TASKS; // schedule round robin style
+        if(preference==-1&&idx==0)continue;
 
 	if(idx==preference||idx==2)continue;// skip sleeper and preferred tasks here.
 
 	esp=scheduler_schedule(idx);
 
-	if(esp)return esp;
+	if(esp){
+            //klog("%d",idx);
+            return esp;
+        }
     }
 
     // force the sleeper task...
@@ -349,9 +368,10 @@ void task_syscall_worker()
 	    task_list[cpu][0].syscall=true; // sleep (syscall misused)
 	}
 	x86_sti();
+
 	if(nowork)
 	{
-	    __asm__("int $0x81"); // wake scheduler!
+	    __asm__("int $0x81"); // wake scheduler! with IPI
 	}
     }
 }
-- 
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