[v1] xen: Fix some bugs in scheduling

[PATCH 3/3] xen/cpupool: fix removing cpu from a cpupool

Posted by Juergen Gross 5 years, 9 months ago

Commit cb563d7665f2 ("xen/sched: support core scheduling for moving
cpus to/from cpupools") introduced a regression when trying to remove
an offline cpu from a cpupool, as the system would crash in this
situation.

Fix that by testing the cpu to be online.

Fixes: cb563d7665f2 ("xen/sched: support core scheduling for moving cpus to/from cpupools")
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 xen/common/sched/cpupool.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index d40345b585..de9e25af84 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -520,6 +520,9 @@ static int cpupool_unassign_cpu(struct cpupool *c, unsigned int cpu)
     debugtrace_printk("cpupool_unassign_cpu(pool=%d,cpu=%d)\n",
                       c->cpupool_id, cpu);
 
+    if ( !cpu_online(cpu) )
+        return -EINVAL;
+
     master_cpu = sched_get_resource_cpu(cpu);
     ret = cpupool_unassign_cpu_start(c, master_cpu);
     if ( ret )
-- 
2.16.4

Re: [PATCH 3/3] xen/cpupool: fix removing cpu from a cpupool

Posted by Dario Faggioli 5 years, 9 months ago

On Thu, 2020-04-30 at 17:15 +0200, Juergen Gross wrote:
> Commit cb563d7665f2 ("xen/sched: support core scheduling for moving
> cpus to/from cpupools") introduced a regression when trying to remove
> an offline cpu from a cpupool, as the system would crash in this
> situation.
> 
> Fix that by testing the cpu to be online.
> 
> Fixes: cb563d7665f2 ("xen/sched: support core scheduling for moving
> cpus to/from cpupools")
> Signed-off-by: Juergen Gross <jgross@suse.com>
>
Acked-by: Dario Faggioli <dfaggioli@suse.com>

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)

Re: [PATCH 3/3] xen/cpupool: fix removing cpu from a cpupool

Posted by Jan Beulich 5 years, 9 months ago

On 07.05.2020 20:36, Dario Faggioli wrote:
> On Thu, 2020-04-30 at 17:15 +0200, Juergen Gross wrote:
>> Commit cb563d7665f2 ("xen/sched: support core scheduling for moving
>> cpus to/from cpupools") introduced a regression when trying to remove
>> an offline cpu from a cpupool, as the system would crash in this
>> situation.
>>
>> Fix that by testing the cpu to be online.
>>
>> Fixes: cb563d7665f2 ("xen/sched: support core scheduling for moving
>> cpus to/from cpupools")
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>
> Acked-by: Dario Faggioli <dfaggioli@suse.com>

Jürgen,

it looks like this is independent of the earlier two patches
and hence could go in, while I understand there'll be v2 for
the earlier ones. Please confirm.

Jan

Re: [PATCH 3/3] xen/cpupool: fix removing cpu from a cpupool

Posted by Jürgen Groß 5 years, 9 months ago

On 08.05.20 10:19, Jan Beulich wrote:
> On 07.05.2020 20:36, Dario Faggioli wrote:
>> On Thu, 2020-04-30 at 17:15 +0200, Juergen Gross wrote:
>>> Commit cb563d7665f2 ("xen/sched: support core scheduling for moving
>>> cpus to/from cpupools") introduced a regression when trying to remove
>>> an offline cpu from a cpupool, as the system would crash in this
>>> situation.
>>>
>>> Fix that by testing the cpu to be online.
>>>
>>> Fixes: cb563d7665f2 ("xen/sched: support core scheduling for moving
>>> cpus to/from cpupools")
>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>>
>> Acked-by: Dario Faggioli <dfaggioli@suse.com>
> 
> Jürgen,
> 
> it looks like this is independent of the earlier two patches
> and hence could go in, while I understand there'll be v2 for
> the earlier ones. Please confirm.

Confirmed.


Juergen

[PATCH 1/3] xen/sched: allow rcu work to happen when syncing cpus in core scheduling
[PATCH 2/3] xen/sched: fix theoretical races accessing vcpu->dirty_cpu
[PATCH 3/3] xen/cpupool: fix removing cpu from a cpupool