Re: Cpuidle drivers,Suspend : Fix suspend/resume hang with intel_idle driver

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On Thursday, June 28, 2012, preeti wrote:
> 
> From: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
> 
> Dave Hansen reported problems with suspend/resume when used
> with intel_idle driver.More such problems were noticed.
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/674075.
> 
> The reason for this could not be suspected till he reported
> resume hang issue when used with acpi idle driver on his Lenovo-S10-3
> Atom netbook.
> 
> The patch-[PM / ACPI: Fix suspend/resume regression caused by cpuidle
> cleanup],fixed this issue by ensuring that acpi idle drivers prevent
> cpus from going into deeper sleep states during suspend to prevent
> resume hang on certain bios.
> http://marc.info/?l=linux-pm&m=133958534231884&w=2
> 
> Commit b04e7bdb984e3b7f62fb7f44146a529f88cc7639
> (ACPI: disable lower idle C-states across suspend/resume) throws
> light on the resume hang issue on certain specific bios.
> 
> Also the following lines in drivers/idle/intel_idle.c suggest intel_idle
> drivers should also ensure cpus are prevented from entering idle states
> during suspend to avoid a resume hang.
> 
> /*
>  * Known limitations
>  * [..]
>  *
>  * ACPI has a .suspend hack to turn off deep c-states during suspend
>  * to avoid complications with the lapic timer workaround.
>  * Have not seen issues with suspend, but may need same workaround here.
>  *
>  */
> This patch aims at having this fix in a place common to both the idle
> drivers.
> 
> Suspend is enabled only if ACPI is active on x86.Thus the setting of
> acpi_idle_suspend during suspend is moved up to ACPI specific code with
> both acpi and intel idle drivers checking if it is valid to enter deeper
> idle states.The setting of acpi_idle_suspend is done via PM_SUSPEND_PREPARE
> notifiers to avoid race conditions between processors entering idle states
> and the ongoing process of suspend.
> 
> The check on acpi_idle_suspend is included in the most appropriate header
> so as to be visible to both the idle drivers irrespective of the
> different configurations.Even if ACPI is disabled intel idle drivers can
> still carry out the acpi_idle_suspend check.
> 
> Reported-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Deepthi Dharwar <deepthi@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
> ---
> Dave, does this patch ensure suspend/resume works
> fine on your netbook if intel_idle driver is enabled?
> 
>  drivers/acpi/processor_idle.c |   46 +++++++++++++++++++----------------------
>  drivers/acpi/sleep.c          |   38 ++++++++++++++++++++++++++++++++++
>  drivers/idle/intel_idle.c     |   10 +++++++++
>  include/linux/suspend.h       |   24 +++++++++++++++++++++
>  4 files changed, 93 insertions(+), 25 deletions(-)
> 
> 
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index c2ffd84..3ab0963 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -41,7 +41,7 @@
>  #include <linux/clockchips.h>
>  #include <linux/cpuidle.h>
>  #include <linux/irqflags.h>
> -
> +#include <linux/suspend.h>
>  /*
>   * Include the apic definitions for x86 to have the APIC timer related defines
>   * available also for UP (on SMP it gets magically included via linux/smp.h).
> @@ -221,10 +221,6 @@ static void lapic_timer_state_broadcast(struct acpi_processor *pr,
>  
>  #endif
>  
> -/*
> - * Suspend / resume control
> - */
> -static int acpi_idle_suspend;
>  static u32 saved_bm_rld;
>  
>  static void acpi_idle_bm_rld_save(void)
> @@ -243,21 +239,13 @@ 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;
>  }

So, this seems to be on top of the "PM / ACPI: Fix suspend/resume regression
caused by cpuidle" patch, right?

>  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;
>  }
>  
> @@ -762,11 +750,13 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
>  		return -EINVAL;
>  
>  	local_irq_disable();
> -
> -	if (acpi_idle_suspend) {
> +	/*
> +	 * Do not enter idle states if you are in suspend path
> +	 */
> +	if (in_suspend_path()) {

This is more than ugly.  Can't you simply use the acpi_idle_suspend _variable_
here?

Besides, why the name of the variable is acpi_idle_suspend, if it is used
by the Intel driver too?

>  		local_irq_enable();
>  		cpu_relax();
> -		return -EINVAL;
> +		return -EBUSY;

That change is made by the "PM / ACPI: Fix suspend/resume regression
caused by cpuidle" patch already.

>  	}
>  
>  	lapic_timer_state_broadcast(pr, cx, 1);
> @@ -838,10 +828,13 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
>  
>  	local_irq_disable();
>  
> -	if (acpi_idle_suspend) {
> +	/*
> +	 * Do not enter idle states if you are in suspend path
> +	 */
> +	if (in_suspend_path()) {
>  		local_irq_enable();
>  		cpu_relax();
> -		return -EINVAL;
> +		return -EBUSY;
>  	}
>  
>  	if (cx->entry_method != ACPI_CSTATE_FFH) {
> @@ -922,12 +915,6 @@ 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;
> -	}

The last version of the "PM / ACPI: Fix suspend/resume regression
caused by cpuidle" patch didn't contain this hunk.

>  
>  	if (!cx->bm_sts_skip && acpi_idle_bm_check()) {
>  		if (drv->safe_state_index >= 0) {
> @@ -935,13 +922,22 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
>  						drv, drv->safe_state_index);
>  		} else {
>  			local_irq_disable();
> -			acpi_safe_halt();
> +			if (!(in_suspend_path()))
> +				acpi_safe_halt();
>  			local_irq_enable();
>  			return -EINVAL;
>  		}
>  	}
>  
>  	local_irq_disable();
> +	/*
> +	 * Do not enter idle states if you are in suspend path
> +	 */
> +	if (in_suspend_path()) {
> +		local_irq_enable();
> +		cpu_relax();
> +		return -EBUSY;
> +	}
>  
>  	if (cx->entry_method != ACPI_CSTATE_FFH) {
>  		current_thread_info()->status &= ~TS_POLLING;
> diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> index 8856102..4ec77db 100644
> --- a/drivers/acpi/sleep.c
> +++ b/drivers/acpi/sleep.c
> @@ -28,6 +28,11 @@
>  #include "internal.h"
>  #include "sleep.h"
>  
> +/*
> + * Suspend/Resume control
> + */
> +int acpi_idle_suspend;
> +
>  u8 wake_sleep_flags = ACPI_NO_OPTIONAL_METHODS;
>  static unsigned int gts, bfs;
>  static int set_param_wake_flag(const char *val, struct kernel_param *kp)
> @@ -905,6 +910,36 @@ static void __init acpi_gts_bfs_check(void)
>  	}
>  }
>  
> +/**
> + * cpuidle_pm_callback - On some bios, resume hangs
> + * if idle states are entered during suspend.
> + *
> + * acpi_idle_suspend is used by the x86 idle drivers
> + * to decide whether to go into idle states or not.
> + */
> +static int
> +cpuidle_pm_callback(struct notifier_block *nb,
> +			unsigned long action, void *ptr)
> +{
> +	switch (action) {
> +
> +	case PM_SUSPEND_PREPARE:
> +		if (acpi_idle_suspend == 0)
> +			acpi_idle_suspend = 1;
> +		break;
> +
> +	case PM_POST_SUSPEND:
> +		if (acpi_idle_suspend == 1)
> +			acpi_idle_suspend = 0;
> +		break;
> +
> +	default:
> +		return NOTIFY_DONE;
> +	}
> +
> +	return NOTIFY_OK;
> +}

Why don't you put this notifier into cpuidle instead?

> +
>  int __init acpi_sleep_init(void)
>  {
>  	acpi_status status;
> @@ -932,6 +967,9 @@ int __init acpi_sleep_init(void)
>  
>  	suspend_set_ops(old_suspend_ordering ?
>  		&acpi_suspend_ops_old : &acpi_suspend_ops);
> +
> +	pm_notifier(cpuidle_pm_callback, 0);
> +
>  #endif
>  
>  #ifdef CONFIG_HIBERNATION
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index d0f59c3..a595207 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -65,6 +65,7 @@
>  #include <asm/cpu_device_id.h>
>  #include <asm/mwait.h>
>  #include <asm/msr.h>
> +#include <linux/suspend.h>
>  
>  #define INTEL_IDLE_VERSION "0.4"
>  #define PREFIX "intel_idle: "
> @@ -255,6 +256,15 @@ static int intel_idle(struct cpuidle_device *dev,
>  	cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
>  
>  	/*
> +	 * Do not enter idle states if you are in suspend path
> +	 */
> +	if (in_suspend_path()) {
> +		local_irq_enable();
> +		cpu_relax();
> +		return -EBUSY;
> +	}
> +
> +	/*
>  	 * leave_mm() to avoid costly and often unnecessary wakeups
>  	 * for flushing the user TLB's associated with the active mm.
>  	 */
> diff --git a/include/linux/suspend.h b/include/linux/suspend.h
> index 0c808d7..eb96670 100644
> --- a/include/linux/suspend.h
> +++ b/include/linux/suspend.h
> @@ -38,6 +38,30 @@ typedef int __bitwise suspend_state_t;
>  #define PM_SUSPEND_MEM		((__force suspend_state_t) 3)
>  #define PM_SUSPEND_MAX		((__force suspend_state_t) 4)
>  
> +extern int acpi_idle_suspend;
> +
> +/**
> + * in_suspend_path - X86 idle drivers make a call
> + * to this function before entering idle states.
> + *
> + * Entering idle states is prevented if it is in suspend
> + * path.
> + */
> +#ifdef CONFIG_ACPI

Why #ifdef CONFIG_ACPI?

> +static inline int in_suspend_path(void)
> +{
> +	if (acpi_idle_suspend == 1)
> +		return 1;
> +	else
> +		return 0;
> +}
> +#else
> +static inline int in_suspend_path(void)
> +{
> +	return 0;
> +}
> +#endif
> +
>  enum suspend_stat_step {
>  	SUSPEND_FREEZE = 1,
>  	SUSPEND_PREPARE,

Thanks,
Rafael
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