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SubjectRe: boot hang on commit "PM / ACPI: Fix suspend/resume regression caused by cpuidle cleanup."
On 06/25/2012 03:48 AM, Rafael J. Wysocki wrote:

> On Friday, June 22, 2012, Fengguang Wu wrote:
>> Hi Deepthi,
>>
>> I can no longer reproduce this issue... Sorry for the noise!
>
> But I do, 100% of the time on real hardware which is Acer Ferrari One.
>
> The symptom is that the new WARN_ON() triggers pretty much on every
> cpuidle transition for me which makes the machine unuseable.
>
> That may be a result of a different bug, but the box evidently works
> without the hunk in arch/x86/kernel/process.c, so I'd prefer to drop it
> for now.

If cpu is coming out of cpuidle with WARN_ON every-time, is suspend
on this device working ? Wanted to get some clarity about this hardware .
We can remove this check for now.

> Moreover, I have a couple of questions regarding the implementation.
>
> First, why are we returning -EINVAL if acpi_idle_suspend is set? Surely,
> something like -EBUSY or -EAGAIN would be better here, wouldn't it?
>


Any negative return value will serve the purpose. We put it as -EINVAL
as cpu_idle operation during suspend was termed invalid. I will change it to
-EBUSY for better readability.

> Second, is the cpu_relax() before returning really necessary?


cpu_relax operation is mainly to lower CPU power consumption.
If the system is idle, we would want to at-least reduce
power consumption. Better than busy looping in and out of idle when
suspend is triggered. There is no harm having it.

>
> Finally, the hunk in acpi_idle_enter_bm() still looks ugly. I'd prefer
> something like this instead:
>
> @@ -907,7 +928,10 @@ static int acpi_idle_enter_bm(struct cpu
> drv, drv->safe_state_index);
> } else {
> local_irq_disable();
> - acpi_safe_halt();
> +
> + if (!acpi_idle_suspend)
> + acpi_safe_halt();
> +
> local_irq_enable();
> return -EINVAL;
> }
> @@ -915,6 +939,12 @@ static int acpi_idle_enter_bm(struct cpu
>
> local_irq_disable();
>
> + if (acpi_idle_suspend) {
> + local_irq_enable();
> + cpu_relax();
> + return -EBUSY;
> + }
> +
> if (cx->entry_method != ACPI_CSTATE_FFH) {
> current_thread_info()->status &= ~TS_POLLING;
> /*
>
> Hmm?


Yes, I'll will re-factor the code.


> The patch has been dropped from the linux-pm tree (hopefully for now).
>
> Thanks,
> Rafael
>
>
>> On Fri, Jun 22, 2012 at 03:26:51PM +0530, Deepthi Dharwar wrote:
>>> Hi,
>>>
>>> This is interesting .. suspend fix breaking boot on kvm.
>>>
>>> We complied and booted fine with mainline kernels including 3.5-rc2 with
>>> this fix on servers and laptops.
>>> So wondering how different is booting on machines Vs
>>> from kvm ?
>>>
>>> Also, are you seeing smooth boot on kvm by reverting only this patch ?
>>>
>>> Cheers
>>> Deepthi
>>>
>>> On 06/22/2012 01:05 PM, wfg@linux.intel.com wrote:
>>>
>>>> Hi Deepthi,
>>>>
>>>> It seems that commit de08622 triggers a boot hang in my kvm boot test.
>>>>
>>>> kvm -cpu kvm64 -enable-kvm \
>>>> -kernel ./gpxelinux.lkrn \
>>>> -initrd ./kvm.gpxe \
>>>> -m 384M \
>>>> -net nic,vlan=0,macaddr=00:00:00:00:00:00,model=e1000 \
>>>> -net user,vlan=0,hostfwd=tcp::$port-:22 \
>>>> -boot order=nc \
>>>> -no-reboot \
>>>> -watchdog i6300esb \
>>>> $(qemu_drives) \
>>>> -pidfile $pidfile \
>>>> -serial file:$dmesg
>>>>
>>>> tree: git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next
>>>> head: de08622731417ba429fc470ab8f2d7c260cb5c72
>>>> commit: de08622731417ba429fc470ab8f2d7c260cb5c72 [9/9] PM / ACPI: Fix suspend/resume regression caused by cpuidle cleanup.
>>>> config: x86_64-allyesdebian (attached as .config)
>>>>
>>>> x86_64-allyesdebian bbbbbbbbbB
>>>> --
>>>> 8: b 0eb8c06 2012-06-19 22:23:37 +0200 PM / Sleep: Separate printing suspend times from initcall_debug
>>>> 9: B de08622 boot hang after [ 81.370898] usbcore: registered new interface driver dw2102
>>>>
>>>> legend: [b] boot fine [B] boot error
>>>>
>>>> commit de08622731417ba429fc470ab8f2d7c260cb5c72
>>>> Author: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
>>>> Date: Wed Jun 13 16:28:17 2012 +0530
>>>>
>>>> PM / ACPI: Fix suspend/resume regression caused by cpuidle cleanup.
>>>>
>>>> Commit e978aa7d7d57d04eb5f88a7507c4fb98577def77 ( cpuidle: Move
>>>> dev->last_residency update to driver enter routine; remove dev->last_state)
>>>> was breaking suspend on laptops, as reported in the below link
>>>> - https://lkml.org/lkml/2011/11/11/164
>>>>
>>>> This was fixed in commit 3439a8da16bcad6b0982ece938c9f8299bb53584
>>>> (ACPI / cpuidle: Remove acpi_idle_suspend (to fix suspend regression)
>>>> by removing acpi_idle_suspend flag.
>>>> - https://lkml.org/lkml/2011/11/14/74
>>>>
>>>> But this fix did not work on all systems
>>>> as Suspend/resume regression was reported on Lenovo S10-3
>>>> recently by Dave.
>>>> - https://lkml.org/lkml/2012/5/27/115
>>>> It looked like with commit e978aa7d broke suspend and
>>>> with commit 3439a8da resume was not working with acpi_idle driver.
>>>>
>>>> This patch fixes the regression that caused this issue
>>>> in the first place. acpi_idle_suspend flag is essential on
>>>> some x86 systems to prevent the cpus from going to deeper C-states
>>>> when suspend is triggered ( commit b04e7bdb984 )
>>>> So reverting the commit 3439a8da is essential.
>>>>
>>>> By default, irqs are disabled in cpu_idle arch specific call
>>>> and re-enabled in idle state return path . As the acpi_idle_suspend
>>>> flag was being set during suspend, which prevented the cpus
>>>> going to deeper idle states, it is essential to
>>>> enabling the irqs in its return path too.
>>>>
>>>> To address the suspend issue,
>>>> we were not re-enabling the interrupts while returning from
>>>> acpi_idle_enter_bm() routine if acpi_idle_suspend flag is set.
>>>> and this was causing suspend failure.
>>>>
>>>> In addition to the above fix, a sanity check has also been added
>>>> in x86 arch specific cpu_idle call to ensure that the idle call
>>>> always returns with IRQs enabled.
>>>>
>>>> Signed-off-by: Deepthi Dharwar <deepthi@linux.vnet.ibm.com>
>>>> Reported-and-Tested-by: Dav Hansen <dave@linux.vnet.ibm.com>
>>>> Tested-by: Preeti Murthy <preeti@linux.vnet.ibm.com>
>>>> Reviewed-by: Srivatsa S Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>>>> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
>>>>
>>>> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
>>>> index 735279e..8ab76ad 100644
>>>> --- a/arch/x86/kernel/process.c
>>>> +++ b/arch/x86/kernel/process.c
>>>> @@ -460,6 +460,12 @@ void cpu_idle(void)
>>>> pm_idle();
>>>>
>>>> rcu_idle_exit();
>>>> +
>>>> + /*
>>>> + * Sanity check to ensure that idle call returns
>>>> + * with IRQs enabled
>>>> + */
>>>> + WARN_ON(irqs_disabled());
>>>> start_critical_timings();
>>>>
>>>> /* In many cases the interrupt that ended idle
>>>> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
>>>> index f3decb3..c2ffd84 100644
>>>> --- a/drivers/acpi/processor_idle.c
>>>> +++ b/drivers/acpi/processor_idle.c
>>>> @@ -224,6 +224,7 @@ static void lapic_timer_state_broadcast(struct acpi_processor *pr,
>>>> /*
>>>> * Suspend / resume control
>>>> */
>>>> +static int acpi_idle_suspend;
>>>> static u32 saved_bm_rld;
>>>>
>>>> static void acpi_idle_bm_rld_save(void)
>>>> @@ -242,13 +243,21 @@ static void acpi_idle_bm_rld_restore(void)
>>>>
>>>> int acpi_processor_suspend(struct acpi_device * device, pm_message_t state)
>>>> {
>>>> + if (acpi_idle_suspend == 1)
>>>> + return 0;
>>>> +
>>>> acpi_idle_bm_rld_save();
>>>> + acpi_idle_suspend = 1;
>>>> return 0;
>>>> }
>>>>
>>>> int acpi_processor_resume(struct acpi_device * device)
>>>> {
>>>> + if (acpi_idle_suspend == 0)
>>>> + return 0;
>>>> +
>>>> acpi_idle_bm_rld_restore();
>>>> + acpi_idle_suspend = 0;
>>>> return 0;
>>>> }
>>>>
>>>> @@ -754,6 +763,12 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
>>>>
>>>> local_irq_disable();
>>>>
>>>> + if (acpi_idle_suspend) {
>>>> + local_irq_enable();
>>>> + cpu_relax();
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> lapic_timer_state_broadcast(pr, cx, 1);
>>>> kt1 = ktime_get_real();
>>>> acpi_idle_do_entry(cx);
>>>> @@ -823,6 +838,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
>>>>
>>>> local_irq_disable();
>>>>
>>>> + if (acpi_idle_suspend) {
>>>> + local_irq_enable();
>>>> + cpu_relax();
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> if (cx->entry_method != ACPI_CSTATE_FFH) {
>>>> current_thread_info()->status &= ~TS_POLLING;
>>>> /*
>>>> @@ -901,6 +922,13 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
>>>> if (unlikely(!pr))
>>>> return -EINVAL;
>>>>
>>>> + if (acpi_idle_suspend) {
>>>> + if (irqs_disabled())
>>>> + local_irq_enable();
>>>> + cpu_relax();
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> if (!cx->bm_sts_skip && acpi_idle_bm_check()) {
>>>> if (drv->safe_state_index >= 0) {
>>>> return drv->states[drv->safe_state_index].enter(dev,
>>>
>>
>>
>
> --
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>


Cheers,
Deepthi



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