sched: fix resuming from S3 with smt=0

When resuming from S3 and smt=0 or maxcpus= are specified we must not
do anything in cpu_schedule_callback(). This is not true today for
taking down a cpu during resume.

If anything goes wrong during resume all the scheduler related error
handling is in cpupool.c, so we can just bail out early from
cpu_schedule_callback() when suspending or resuming.

This fixes commit 0763cd2687897b55e7 ("xen/sched: don't disable
scheduler on cpus during suspend").

Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>

diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index e70cc70a65ac47dc7c6e914c427e6320f8d0ed3e..54a07ff9e802f2fccdcadcf4d4c2613b06f49f53 100644 (file)
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -2562,6 +2562,13 @@ static int cpu_schedule_callback(
     unsigned int cpu = (unsigned long)hcpu;
     int rc = 0;
 
+    /*
+     * All scheduler related suspend/resume handling needed is done in
+     * cpupool.c.
+     */
+    if ( system_state > SYS_STATE_active )
+        return NOTIFY_DONE;
+
     rcu_read_lock(&sched_res_rculock);
 
     /*
@@ -2589,8 +2596,7 @@ static int cpu_schedule_callback(
     switch ( action )
     {
     case CPU_UP_PREPARE:
-        if ( system_state != SYS_STATE_resume )
-            rc = cpu_schedule_up(cpu);
+        rc = cpu_schedule_up(cpu);
         break;
     case CPU_DOWN_PREPARE:
         rcu_read_lock(&domlist_read_lock);
@@ -2598,13 +2604,10 @@ static int cpu_schedule_callback(
         rcu_read_unlock(&domlist_read_lock);
         break;
     case CPU_DEAD:
-        if ( system_state == SYS_STATE_suspend )
-            break;
         sched_rm_cpu(cpu);
         break;
     case CPU_UP_CANCELED:
-        if ( system_state != SYS_STATE_resume )
-            cpu_schedule_down(cpu);
+        cpu_schedule_down(cpu);
         break;
     default:
         break;