[Xen-changelog] [xen stable-4.13] sched: fix resuming from S3 with smt=0

[patchbot@xxxxxxx]

commit 3baeeedc9f796f6ef5595c2999a4135f28e1a4ab
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Wed Jan 15 14:24:09 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jan 15 14:24:09 2020 +0100

    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@xxxxxxxxxxxxxxxxxxxxxx>
    Tested-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    master commit: d7f3c76317108ee9989f00545d394fa495fba752
    master date: 2020-01-08 14:59:25 +0100
---
 xen/common/schedule.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index e70cc70a65..54a07ff9e8 100644
--- 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;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13

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