On Tuesday, March 11, 2014 09:52:42 PM Rafael J. Wysocki wrote:
> On Tuesday, March 11, 2014 01:17:20 PM Dirk Brandewie wrote:
> > On 03/11/2014 01:20 PM, Rafael J. Wysocki wrote:
> > > On Tuesday, March 11, 2014 10:58:59 AM Dirk Brandewie wrote:
> > >> Hi Patrick,
> > >>
> > >> Sorry for the slow response you caught me taking a few days off :-)
> > >>
> > >> On 03/07/2014 07:49 AM, Patrik Lundquist wrote:
> > >>> Hi,
> > >>>
> > >>> booting 3.13.5 on a dual socket Ivy Bridge-EP resulted in this error:
> > >>>
> > >>> [ 0.194139] smpboot: CPU0: Intel(R) Xeon(R) CPU E5-2687W v2 @
> > >>> 3.40GHz (fam: 06, model: 3e, stepping: 04)
> > >>> ...
> > >>> [ 0.246755] x86: Booting SMP configuration:
> > >>> [ 0.250935] .... node #0, CPUs: #1 #2 #3 #4 #5 #6 #7
> > >>> [ 0.357648] .... node #1, CPUs: #8 #9 #10 #11 #12 #13 #14 #15
> > >>> [ 0.553293] x86: Booted up 2 nodes, 16 CPUs
> > >>> [ 0.557666] smpboot: Total of 16 processors activated (108850.19 BogoMIPS)
> > >>> ...
> > >>> [ 5.210204] Intel P-state driver initializing.
> > >>> [ 5.232407] Intel pstate controlling: cpu 0
> > >>> [ 5.253628] Intel pstate controlling: cpu 1
> > >>> [ 5.274899] cpufreq: __cpufreq_add_dev: ->get() failed
> > >>> [ 5.294856] Intel pstate controlling: cpu 2
> > >>> [ 5.313553] Intel pstate controlling: cpu 3
> > >>> [ 5.332526] Intel pstate controlling: cpu 4
> > >>> [ 5.352347] Intel pstate controlling: cpu 5
> > >>> [ 5.372112] Intel pstate controlling: cpu 6
> > >>> [ 5.391097] Intel pstate controlling: cpu 7
> > >>> [ 5.410272] Intel pstate controlling: cpu 8
> > >>> [ 5.429092] Intel pstate controlling: cpu 9
> > >>> [ 5.447714] Intel pstate controlling: cpu 10
> > >>> [ 5.465872] Intel pstate controlling: cpu 11
> > >>> [ 5.482942] Intel pstate controlling: cpu 12
> > >>> [ 5.498414] Intel pstate controlling: cpu 13
> > >>> [ 5.513586] Intel pstate controlling: cpu 14
> > >>> [ 5.529200] Intel pstate controlling: cpu 15
> > >>>
> > >>> CPU 1 is alive and well but missing the cpufreq driver. The system is
> > >>> running fine otherwise.
> > >>
> > >> This is a regression introduced by commit
> > >> da60ce9f2fa cpufreq: call cpufreq_driver->get() after calling ->init()
> > >
> > > So the problem is that ->get() may return 0 in intel_pstate and that causes
> > > the core's _add function to abort? That would mean sample->freq equal to 0,
> > > which shouldn't happen after intel_pstate_sample() called by intel_pstate_init_cpu().
> > >
> > > Or am I missing anything?
> > >
> >
> > The problem is that the core has been running less than 1% of the time based on
> > the absolute values of aperf/mperf and the second sample has not been taken to
> > get a more precise delta.
> >
> > I thought about running sample twice during init but didn't want to propose it
> > until I made sure I was not going to break anything else.
>
> Well, ->setpolicy drivers are a special case anyway, so we can simply skip the
> current frequency updates in __cpufreq_add_dev() and cpufreq_update_policy()
> for them.
In other words, we can do something like in the patch below I suppose?
Rafael
---
drivers/cpufreq/cpufreq.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1137,7 +1137,7 @@ static int __cpufreq_add_dev(struct devi
per_cpu(cpufreq_cpu_data, j) = policy;
write_unlock_irqrestore(&cpufreq_driver_lock, flags);
- if (cpufreq_driver->get) {
+ if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
policy->cur = cpufreq_driver->get(policy->cpu);
if (!policy->cur) {
pr_err("%s: ->get() failed\n", __func__);
@@ -2150,7 +2150,7 @@ int cpufreq_update_policy(unsigned int c
* BIOS might change freq behind our back
* -> ask driver for current freq and notify governors about a change
*/
- if (cpufreq_driver->get) {
+ if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
new_policy.cur = cpufreq_driver->get(cpu);
if (WARN_ON(!new_policy.cur)) {
ret = -EIO;
--
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