Re: [PATCH] xen/sched: fix get_cpu_idle_time() for smt=0 suspend/resume

[Juergen Gross]

On 18.08.21 12:35, Jan Beulich wrote:

On 18.08.2021 12:21, Juergen Gross wrote:

With smt=0 during a suspend/resume cycle of the machine the threads
which have been parked before will briefly come up again. This can
result in problems e.g. with cpufreq driver being active as this will
call into get_cpu_idle_time() for a cpu without initialized scheduler
data.

Fix that by letting get_cpu_idle_time() deal with this case.

Fixes: 132cbe8f35632fb2 ("sched: fix get_cpu_idle_time() with core scheduling")
Reported-by: Marek Marczykowski-Górecki <marma...@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgr...@suse.com>
Tested-by: Marek Marczykowski-Górecki <marma...@invisiblethingslab.com>

Reviewed-by: Jan Beulich <jbeul...@suse.com>

--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -337,7 +337,7 @@ uint64_t get_cpu_idle_time(unsigned int cpu)
      struct vcpu_runstate_info state = { 0 };
      const struct vcpu *v = idle_vcpu[cpu];

+    if ( cpu_online(cpu) && v && get_sched_res(cpu) )
          vcpu_runstate_get(v, &state);

- if ( cpu_online(cpu) && v )

My earlier question was aiming at getting rid of the (now) middle part
of the condition; I thought this may be okay to do as a secondary change
here. But perhaps you intentionally left it there, so I'm unsure whether
to suggest to make the adjustment while committing (awaiting a
maintainer ack first anyway).

Ah, okay. Yes, I think the test of v being non-NULL can be removed.


Juergen

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