[Xen-changelog] [xen stable-4.12] xen/sched: fix csched2_deinit_pdata()

[patchbot@xxxxxxx]

commit a324e9c460227229a1bd4c2e896a0f31e5843dc5
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Tue Jun 4 15:39:37 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jun 4 15:39:37 2019 +0200

    xen/sched: fix csched2_deinit_pdata()
    
    Commit 753ba43d6d16e688 ("xen/sched: fix credit2 smt idle handling")
    introduced a regression when switching cpus between cpupools.
    
    When assigning a cpu to a cpupool with credit2 being the default
    scheduler csched2_deinit_pdata() is called for the credit2 private data
    after the new scheduler's private data has been hooked to the per-cpu
    scheduler data. Unfortunately csched2_deinit_pdata() will cycle through
    all per-cpu scheduler areas it knows of for removing the cpu from the
    respective sibling masks including the area of the just moved cpu. This
    will (depending on the new scheduler) either clobber the data of the
    new scheduler or in case of sched_rt lead to a crash.
    
    Avoid that by removing the cpu from the list of active cpus in credit2
    data first.
    
    The opposite problem is occurring when removing a cpu from a cpupool:
    init_pdata() of credit2 will access the per-cpu data of the old
    scheduler.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
    master commit: ffd3367ed682b6ac6f57fcb151921054dd4cce7e
    master date: 2019-05-17 15:41:17 +0200
---
 xen/common/sched_credit2.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index 6958b265fc..9c1c3b4e08 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -3813,22 +3813,21 @@ init_pdata(struct csched2_private *prv, struct 
csched2_pcpu *spc,
         activate_runqueue(prv, spc->runq_id);
     }
 
-    __cpumask_set_cpu(cpu, &rqd->idle);
-    __cpumask_set_cpu(cpu, &rqd->active);
-    __cpumask_set_cpu(cpu, &prv->initialized);
-    __cpumask_set_cpu(cpu, &rqd->smt_idle);
+    __cpumask_set_cpu(cpu, &spc->sibling_mask);
 
-    /* On the boot cpu we are called before cpu_sibling_mask has been set up. 
*/
-    if ( cpu == 0 && system_state < SYS_STATE_active )
-        __cpumask_set_cpu(cpu, &csched2_pcpu(cpu)->sibling_mask);
-    else
+    if ( cpumask_weight(&rqd->active) > 0 )
         for_each_cpu ( rcpu, per_cpu(cpu_sibling_mask, cpu) )
             if ( cpumask_test_cpu(rcpu, &rqd->active) )
             {
                 __cpumask_set_cpu(cpu, &csched2_pcpu(rcpu)->sibling_mask);
-                __cpumask_set_cpu(rcpu, &csched2_pcpu(cpu)->sibling_mask);
+                __cpumask_set_cpu(rcpu, &spc->sibling_mask);
             }
 
+    __cpumask_set_cpu(cpu, &rqd->idle);
+    __cpumask_set_cpu(cpu, &rqd->active);
+    __cpumask_set_cpu(cpu, &prv->initialized);
+    __cpumask_set_cpu(cpu, &rqd->smt_idle);
+
     if ( cpumask_weight(&rqd->active) == 1 )
         rqd->pick_bias = cpu;
 
@@ -3937,13 +3936,13 @@ csched2_deinit_pdata(const struct scheduler *ops, void 
*pcpu, int cpu)
 
     printk(XENLOG_INFO "Removing cpu %d from runqueue %d\n", cpu, 
spc->runq_id);
 
-    for_each_cpu ( rcpu, &rqd->active )
-        __cpumask_clear_cpu(cpu, &csched2_pcpu(rcpu)->sibling_mask);
-
     __cpumask_clear_cpu(cpu, &rqd->idle);
     __cpumask_clear_cpu(cpu, &rqd->smt_idle);
     __cpumask_clear_cpu(cpu, &rqd->active);
 
+    for_each_cpu ( rcpu, &rqd->active )
+        __cpumask_clear_cpu(cpu, &csched2_pcpu(rcpu)->sibling_mask);
+
     if ( cpumask_empty(&rqd->active) )
     {
         printk(XENLOG_INFO " No cpus left on runqueue, disabling\n");
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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