[xen stable-4.20] xen/sched: fix arinc653 to not use variables across cpupools

[patchbot@xxxxxxx]

commit 80cbb296127b6c1729f4625498b27cdb41bb614b
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Thu Mar 20 12:53:29 2025 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 20 12:53:29 2025 +0100

    xen/sched: fix arinc653 to not use variables across cpupools
    
    a653sched_do_schedule() is using two function local static variables,
    which is resulting in bad behavior when using more than one cpupool
    with the arinc653 scheduler.
    
    Fix that by moving those variables to the scheduler private data.
    
    Fixes: 22787f2e107c ("ARINC 653 scheduler")
    Reported-by: Choi Anderson <Anderson.Choi@xxxxxxxxxx>
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Nathan Studer <nathan.studer@xxxxxxxxxxxxxxx>
    master commit: d0561ac8ab0e780b1e8ab41d0d15e9f9b076dee3
    master date: 2025-03-14 10:17:11 +0100
---
 xen/common/sched/arinc653.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/xen/common/sched/arinc653.c b/xen/common/sched/arinc653.c
index a82c0d7314..9ebae6d7ae 100644
--- a/xen/common/sched/arinc653.c
+++ b/xen/common/sched/arinc653.c
@@ -143,6 +143,12 @@ typedef struct a653sched_priv_s
      * pointers to all Xen UNIT structures for iterating through
      */
     struct list_head unit_list;
+
+    /**
+     * scheduling house keeping variables
+     */
+    unsigned int sched_index;
+    s_time_t next_switch_time;
 } a653sched_priv_t;
 
 /**************************************************************************
@@ -513,8 +519,6 @@ a653sched_do_schedule(
     bool tasklet_work_scheduled)
 {
     struct sched_unit *new_task = NULL;
-    static unsigned int sched_index = 0;
-    static s_time_t next_switch_time;
     a653sched_priv_t *sched_priv = SCHED_PRIV(ops);
     const unsigned int cpu = sched_get_resource_cpu(smp_processor_id());
     unsigned long flags;
@@ -528,18 +532,19 @@ a653sched_do_schedule(
         /* time to enter a new major frame
          * the first time this function is called, this will be true */
         /* start with the first domain in the schedule */
-        sched_index = 0;
+        sched_priv->sched_index = 0;
         sched_priv->next_major_frame = now + sched_priv->major_frame;
-        next_switch_time = now + sched_priv->schedule[0].runtime;
+        sched_priv->next_switch_time = now + sched_priv->schedule[0].runtime;
     }
     else
     {
-        while ( (now >= next_switch_time)
-                && (sched_index < sched_priv->num_schedule_entries) )
+        while ( (now >= sched_priv->next_switch_time) &&
+                (sched_priv->sched_index < sched_priv->num_schedule_entries) )
         {
             /* time to switch to the next domain in this major frame */
-            sched_index++;
-            next_switch_time += sched_priv->schedule[sched_index].runtime;
+            sched_priv->sched_index++;
+            sched_priv->next_switch_time +=
+                sched_priv->schedule[sched_priv->sched_index].runtime;
         }
     }
 
@@ -547,8 +552,8 @@ a653sched_do_schedule(
      * If we exhausted the domains in the schedule and still have time left
      * in the major frame then switch next at the next major frame.
      */
-    if ( sched_index >= sched_priv->num_schedule_entries )
-        next_switch_time = sched_priv->next_major_frame;
+    if ( sched_priv->sched_index >= sched_priv->num_schedule_entries )
+        sched_priv->next_switch_time = sched_priv->next_major_frame;
 
     /*
      * If there are more domains to run in the current major frame, set
@@ -556,8 +561,8 @@ a653sched_do_schedule(
      * Otherwise, set new_task equal to the address of the idle task's
      * sched_unit structure.
      */
-    new_task = (sched_index < sched_priv->num_schedule_entries)
-        ? sched_priv->schedule[sched_index].unit
+    new_task = (sched_priv->sched_index < sched_priv->num_schedule_entries)
+        ? sched_priv->schedule[sched_priv->sched_index].unit
         : IDLETASK(cpu);
 
     /* Check to see if the new task can be run (awake & runnable). */
@@ -589,7 +594,7 @@ a653sched_do_schedule(
      * Return the amount of time the next domain has to run and the address
      * of the selected task's UNIT structure.
      */
-    prev->next_time = next_switch_time - now;
+    prev->next_time = sched_priv->next_switch_time - now;
     prev->next_task = new_task;
     new_task->migrated = false;
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.20