[Xen-changelog] [xen master] sched: fix a potential issue with core scheduling

[patchbot@xxxxxxx]

commit 0aaad752be6d7ac683b0ffba0146ddb9520a877c
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Tue Nov 12 11:09:11 2019 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Nov 12 11:09:11 2019 +0100

    sched: fix a potential issue with core scheduling
    
    cpupool_online_cpumask() is used by credit and rt scheduler. It returns
    all the cpus of a cpupool or all online cpus in case no cpupool is
    specified.
    
    The "no cpupool" case can be dropped, as no scheduler other than the
    init scheduler will ever work on cpus not associated with any cpupool.
    
    As the individual schedulers should only ever work on scheduling
    resources instead of individual cpus, their cpupool_online_cpumask()
    use should be replaced by cpupool->res_valid.
    
    Note that only with core scheduling active this might result in
    potential problems, as with cpu scheduling both masks are identical.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/common/sched_credit.c  | 3 +--
 xen/common/sched_rt.c      | 4 ++--
 xen/include/xen/sched-if.h | 3 ---
 3 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index fbffcf3996..645cdc5e9a 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -1684,12 +1684,11 @@ csched_load_balance(struct csched_private *prv, int cpu,
     struct cpupool *c = get_sched_res(cpu)->cpupool;
     struct csched_unit *speer;
     cpumask_t workers;
-    cpumask_t *online;
+    cpumask_t *online = c->res_valid;
     int peer_cpu, first_cpu, peer_node, bstep;
     int node = cpu_to_node(cpu);
 
     BUG_ON(get_sched_res(cpu) != snext->unit->res);
-    online = cpupool_online_cpumask(c);
 
     /*
      * If this CPU is going offline, or is not (yet) part of any cpupool
diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 6e93e50acb..b2b29481f3 100644
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -774,8 +774,8 @@ rt_deinit_pdata(const struct scheduler *ops, void *pcpu, 
int cpu)
 
     if ( prv->repl_timer.cpu == cpu )
     {
-        struct cpupool *c = get_sched_res(cpu)->cpupool;
-        unsigned int new_cpu = cpumask_cycle(cpu, cpupool_online_cpumask(c));
+        cpumask_t *online = get_sched_res(cpu)->cpupool->res_valid;
+        unsigned int new_cpu = cpumask_cycle(cpu, online);
 
         /*
          * Make sure the timer run on one of the cpus that are still available
diff --git a/xen/include/xen/sched-if.h b/xen/include/xen/sched-if.h
index 29715652bc..b0ac54e63d 100644
--- a/xen/include/xen/sched-if.h
+++ b/xen/include/xen/sched-if.h
@@ -545,9 +545,6 @@ struct cpupool
     enum sched_gran  gran;
 };
 
-#define cpupool_online_cpumask(_pool) \
-    (((_pool) == NULL) ? &cpu_online_map : (_pool)->cpu_valid)
-
 static inline cpumask_t *cpupool_domain_master_cpumask(const struct domain *d)
 {
     /*
--
generated by git-patchbot for /home/xen/git/xen.git#master

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