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SubjectRe: [PATCH 2/5] cpufreq: star/stop cpufreq timers on cpu hotplug
From
Hi Fabio,

Sorry for waking up very late :)

The reason why i am starting this thread again is due to problem
reported by Joseph,
with latest linux-next/master branch (which contains few big patches
from me :) ):

Reboot is giving following to him:

* Will now halt
[ 193.756068] Disabling non-boot CPUs...
[ 193.760088] BUG: scheduling while atomic: halt/780/0x00000002
[ 193.765845] Modules linked in: brcmfmac brcmutil
[ 193.770613] [<c0014990>] (unwind_backtrace+0x0/0xf8) from [<c0049510>]
(__schedule_bug+0x44/0x5c)
[ 193.779548] [<c0049510>] (__schedule_bug+0x44/0x5c) from [<c04fa320>]
(__schedule+0x688/0x6ec)
[ 193.788206] [<c04fa320>] (__schedule+0x688/0x6ec) from [<c04fa75c>]
(schedule_preempt_disabled+0x24/0x34)
[ 193.797811] [<c04fa75c>] (schedule_preempt_disabled+0x24/0x34) from
[<c04f916c>] (__mutex_lock_slowpath+0x170/0x34c)
[ 193.808367] [<c04f916c>] (__mutex_lock_slowpath+0x170/0x34c) from
[<c04f9354>] (mutex_lock+0xc/0x24)
[ 193.817554] [<c04f9354>] (mutex_lock+0xc/0x24) from [<c04f1cdc>]
(unregister_cpu_notifier+0xc/0x24)
[ 193.826640] [<c04f1cdc>] (unregister_cpu_notifier+0xc/0x24) from
[<c033a8a4>] (cpufreq_governor_dbs+0x118/0x614)
[ 193.836866] [<c033a8a4>] (cpufreq_governor_dbs+0x118/0x614) from
[<c033747c>] (__cpufreq_governor+0x58/0xc0)
[ 193.846737] [<c033747c>] (__cpufreq_governor+0x58/0xc0) from
[<c0339104>] (__cpufreq_remove_dev.clone.7+0x58/0x320)
[ 193.857207] [<c0339104>] (__cpufreq_remove_dev.clone.7+0x58/0x320)
from [<c04f7958>] (cpufreq_cpu_callback+0x8c/0x9c)
[ 193.867850] [<c04f7958>] (cpufreq_cpu_callback+0x8c/0x9c) from
[<c0044f4c>] (notifier_call_chain+0x44/0x84)
[ 193.877623] [<c0044f4c>] (notifier_call_chain+0x44/0x84) from
[<c0026e24>] (__cpu_notify+0x2c/0x48)
[ 193.886704] [<c0026e24>] (__cpu_notify+0x2c/0x48) from [<c04f1b08>]
(_cpu_down+0xb0/0x23c)
[ 193.895004] [<c04f1b08>] (_cpu_down+0xb0/0x23c) from [<c00270ec>]
(disable_nonboot_cpus+0x68/0x104)
[ 193.904089] [<c00270ec>] (disable_nonboot_cpus+0x68/0x104) from
[<c0034fbc>] (kernel_power_off+0x24/0x48)
[ 193.913688] [<c0034fbc>] (kernel_power_off+0x24/0x48) from
[<c0035810>] (sys_reboot+0x104/0x1e0)
[ 193.922517] [<c0035810>] (sys_reboot+0x104/0x1e0) from [<c000e520>]
(ret_fast_syscall+0x0/0x30)


And the crash log show this patch of yours somewhere :)

First question: Is this patch still required? Because following patch from me is
sending a STOP/START to governors on cpu hot-[un]plug ?

commit dbcb63407c095af73f3464767e00902cdee55e8b
Author: Viresh Kumar <viresh.kumar@linaro.org>
Date: Sat Jan 12 05:14:39 2013 +0000

cpufreq: Notify governors when cpus are hot-[un]plugged


For me, the answer is NO.

Over that, i tried these patches on ARM bigLITTLE TC2 (3 A7's and 2 A15's) and
my system wasn't booting at all for ondemand governor. Reverting your patch does
fix the issue:

[ 2.613573] arm_big_little: bL_cpufreq_init: Initialized, cpu: 0, cluster 0
[ 2.635436] arm_big_little: bL_cpufreq_init: Initialized, cpu: 2, cluster 1
[ 23.650184] INFO: rcu_sched self-detected stall on CPU { 0}
(t=2100 jiffies g=4294967088 c=4294967087 q=10)
[ 23.679664] Backtrace for cpu 0 (current):
[ 23.680239] INFO: rcu_sched detected stalls on CPUs/tasks: { 0}
(detected by 2, t=2103 jiffies, g=4294967088, c=4294967087, q=10)
[ 23.726839] [<c0014020>] (unwind_backtrace+0x0/0xf8) from
[<c0012f60>] (smp_send_all_cpu_backtrace+0x60/0xcc)
[ 23.756545] [<c0012f60>] (smp_send_all_cpu_backtrace+0x60/0xcc)
from [<c008232c>] (rcu_pending+0x2c8/0x63c)
[ 23.785731] [<c008232c>] (rcu_pending+0x2c8/0x63c) from
[<c0083854>] (rcu_check_callbacks+0x7c/0x148)
[ 23.813358] [<c0083854>] (rcu_check_callbacks+0x7c/0x148) from
[<c002d1e0>] (update_process_times+0x38/0x68)
[ 23.842808] [<c002d1e0>] (update_process_times+0x38/0x68) from
[<c0066b00>] (tick_sched_handle+0x48/0x54)
[ 23.871472] [<c0066b00>] (tick_sched_handle+0x48/0x54) from
[<c0066d6c>] (tick_sched_timer+0x44/0x74)
[ 23.899098] [<c0066d6c>] (tick_sched_timer+0x44/0x74) from
[<c00416d8>] (__run_hrtimer+0x84/0x1b4)
[ 23.925940] [<c00416d8>] (__run_hrtimer+0x84/0x1b4) from
[<c004224c>] (hrtimer_interrupt+0x108/0x2d4)
[ 23.953563] [<c004224c>] (hrtimer_interrupt+0x108/0x2d4) from
[<c0013990>] (arch_timer_handler_virt+0x30/0x38)
[ 23.983530] [<c0013990>] (arch_timer_handler_virt+0x30/0x38) from
[<c007e41c>] (handle_percpu_devid_irq+0x74/0x110)
[ 24.014799] [<c007e41c>] (handle_percpu_devid_irq+0x74/0x110) from
[<c007ac8c>] (generic_handle_irq+0x20/0x30)
[ 24.044765] [<c007ac8c>] (generic_handle_irq+0x20/0x30) from
[<c000e9f4>] (handle_IRQ+0x38/0x94)
[ 24.071085] [<c000e9f4>] (handle_IRQ+0x38/0x94) from [<c0008570>]
(gic_handle_irq+0x28/0x5c)
[ 24.096362] [<c0008570>] (gic_handle_irq+0x28/0x5c) from
[<c000dd80>] (__irq_svc+0x40/0x50)
[ 24.121374] Exception stack(0xef047ec0 to 0xef047f08)
[ 24.136492] 7ec0: 00000000 c0591780 00000000 c0591798 c0591780
c05d5d60 00000000 c0593280
[ 24.160986] 7ee0: c0552c98 c02b1df4 ef046000 00000000 c059179c
ef047f08 c03b5f84 c0043698
[ 24.185477] 7f00: a0000113 ffffffff
[ 24.195910] [<c000dd80>] (__irq_svc+0x40/0x50) from [<c0043698>]
(raw_notifier_chain_register+0x24/0x54)
[ 24.224314] [<c0043698>] (raw_notifier_chain_register+0x24/0x54)
from [<c03b5f84>] (register_cpu_notifier+0x18/0x2c)
[ 24.255843] [<c03b5f84>] (register_cpu_notifier+0x18/0x2c) from
[<c02ab1b0>] (cpufreq_register_driver+0x134/0x190)
[ 24.286852] [<c02ab1b0>] (cpufreq_register_driver+0x134/0x190) from
[<c02b1930>] (bL_cpufreq_register+0x68/0xd4)
[ 24.317337] [<c02b1930>] (bL_cpufreq_register+0x68/0xd4) from
[<c0008740>] (do_one_initcall+0x110/0x178)
[ 24.345738] [<c0008740>] (do_one_initcall+0x110/0x178) from
[<c03b5994>] (kernel_init+0x194/0x330)
[ 24.372577] [<c03b5994>] (kernel_init+0x194/0x330) from
[<c000e1d8>] (ret_from_fork+0x14/0x3c)
[ 24.398371]


On Thu, Dec 27, 2012 at 8:25 PM, Fabio Baltieri
<fabio.baltieri@linaro.org> wrote:
> Add a CPU notifier to start and stop individual core timers on CPU
> hotplug events when running on CPUs with SW coordinated frequency.
>
> Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
> ---
> drivers/cpufreq/cpufreq_governor.c | 51 ++++++++++++++++++++++++++++++++++++++
> 1 file changed, 51 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
> index b0e4506..e881250 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -25,9 +25,12 @@
> #include <linux/tick.h>
> #include <linux/types.h>
> #include <linux/workqueue.h>
> +#include <linux/cpu.h>
>
> #include "cpufreq_governor.h"
>
> +static DEFINE_PER_CPU(struct dbs_data *, cpu_cur_dbs);
> +
> static inline u64 get_cpu_idle_time_jiffy(unsigned int cpu, u64 *wall)
> {
> u64 idle_time;
> @@ -185,6 +188,46 @@ static inline void dbs_timer_exit(struct cpu_dbs_common_info *cdbs)
> cancel_delayed_work_sync(&cdbs->work);
> }
>
> +static int __cpuinit cpu_callback(struct notifier_block *nfb,
> + unsigned long action, void *hcpu)
> +{
> + unsigned int cpu = (unsigned long)hcpu;
> + struct device *cpu_dev = get_cpu_device(cpu);
> + struct dbs_data *dbs_data = per_cpu(cpu_cur_dbs, cpu);
> + struct cpu_dbs_common_info *cpu_cdbs = dbs_data->get_cpu_cdbs(cpu);
> + unsigned int sampling_rate;
> +
> + if (dbs_data->governor == GOV_CONSERVATIVE) {
> + struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
> + sampling_rate = cs_tuners->sampling_rate;
> + } else {
> + struct od_dbs_tuners *od_tuners = dbs_data->tuners;
> + sampling_rate = od_tuners->sampling_rate;
> + }
> +
> + if (cpu_dev) {
> + switch (action) {
> + case CPU_ONLINE:
> + case CPU_ONLINE_FROZEN:
> + case CPU_DOWN_FAILED:
> + case CPU_DOWN_FAILED_FROZEN:
> + dbs_timer_init(dbs_data, cpu_cdbs,
> + sampling_rate, cpu);
> + break;
> + case CPU_DOWN_PREPARE:
> + case CPU_DOWN_PREPARE_FROZEN:
> + dbs_timer_exit(cpu_cdbs);
> + break;
> + }
> + }
> +
> + return NOTIFY_OK;
> +}
> +
> +static struct notifier_block __refdata ondemand_cpu_notifier = {

Over that, why is it called ondemand here ?

> + .notifier_call = cpu_callback,
> +};
> +
> int cpufreq_governor_dbs(struct dbs_data *dbs_data,
> struct cpufreq_policy *policy, unsigned int event)
> {
> @@ -296,7 +339,11 @@ second_time:
> j_cdbs = dbs_data->get_cpu_cdbs(j);
> dbs_timer_init(dbs_data, j_cdbs,
> *sampling_rate, j);
> +
> + per_cpu(cpu_cur_dbs, j) = dbs_data;
> }
> +
> + register_hotcpu_notifier(&ondemand_cpu_notifier);
> } else {
> dbs_timer_init(dbs_data, cpu_cdbs, *sampling_rate, cpu);
> }
> @@ -307,11 +354,15 @@ second_time:
> cs_dbs_info->enable = 0;
>
> if (dbs_sw_coordinated_cpus(cpu_cdbs)) {
> + unregister_hotcpu_notifier(&ondemand_cpu_notifier);
> +
> for_each_cpu(j, policy->cpus) {
> struct cpu_dbs_common_info *j_cdbs;
>
> j_cdbs = dbs_data->get_cpu_cdbs(j);
> dbs_timer_exit(j_cdbs);
> +
> + per_cpu(cpu_cur_dbs, j) = NULL;
> }
> } else {
> dbs_timer_exit(cpu_cdbs);

--
viresh


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