Re: v3.13.5 intel_pstate: cpufreq: __cpufreq_add_dev: ->get() failed

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On 03/11/2014 01:57 PM, Rafael J. Wysocki wrote:
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;

or use has_target()


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