linux-kernel - Re: [PATCH 1/4 v2] PM / suspend: Prevent might sleep splats

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Message-ID: <3248611.5SzSOzXIZe@aspire.rjw.lan>
Date:   Tue, 29 May 2018 10:49:01 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4 v2] PM / suspend: Prevent might sleep splats

On Friday, May 25, 2018 5:54:41 PM CEST Sebastian Andrzej Siewior wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> timekeeping suspend/resume calls read_persistent_clock() which takes
> rtc_lock. That results in might sleep warnings because at that point
> we run with interrupts disabled.
> 
> We cannot convert rtc_lock to a raw spinlock as that would trigger
> other might sleep warnings.
> 
> As a workaround we disable the might sleep warnings by setting
> system_state to SYSTEM_SUSPEND before calling sysdev_suspend() and
> restoring it to SYSTEM_RUNNING afer sysdev_resume(). There is no lock
> contention because hibernate / suspend to RAM is single-CPU at this
> point.
> 
> In s2idle's case the system_state is set to SYSTEM_SUSPEND before
> timekeeping_suspend() which is invoked by the last CPU. In the resume
> case it set back to SYSTEM_RUNNING after timekeeping_resume() which is
> invoked by the first CPU in the resume case. The other CPUs will block
> on tick_freeze_lock.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> [bigeasy: cover s2idle in tick_freeze() / tick_unfreeze()]
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
> v1…v2: Moved the s2idle case into tick_freeze()/unfreeze() as suggested
>        by Rafael (tglx was okay with this).
> 
>  include/linux/kernel.h    | 1 +
>  kernel/power/hibernate.c  | 7 +++++++
>  kernel/power/suspend.c    | 4 ++++
>  kernel/time/tick-common.c | 2 ++
>  4 files changed, 14 insertions(+)
> 
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 6a1eb0b0aad9..7aed92624531 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -542,6 +542,7 @@ extern enum system_states {
>  	SYSTEM_HALT,
>  	SYSTEM_POWER_OFF,
>  	SYSTEM_RESTART,
> +	SYSTEM_SUSPEND,
>  } system_state;
>  
>  /* This cannot be an enum because some may be used in assembly source. */
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 5454cc639a8d..9c85c7822383 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -287,6 +287,8 @@ static int create_image(int platform_mode)
>  
>  	local_irq_disable();
>  
> +	system_state = SYSTEM_SUSPEND;
> +
>  	error = syscore_suspend();
>  	if (error) {
>  		pr_err("Some system devices failed to power down, aborting hibernation\n");
> @@ -317,6 +319,7 @@ static int create_image(int platform_mode)
>  	syscore_resume();
>  
>   Enable_irqs:
> +	system_state = SYSTEM_RUNNING;
>  	local_irq_enable();
>  
>   Enable_cpus:
> @@ -445,6 +448,7 @@ static int resume_target_kernel(bool platform_mode)
>  		goto Enable_cpus;
>  
>  	local_irq_disable();
> +	system_state = SYSTEM_SUSPEND;
>  
>  	error = syscore_suspend();
>  	if (error)
> @@ -478,6 +482,7 @@ static int resume_target_kernel(bool platform_mode)
>  	syscore_resume();
>  
>   Enable_irqs:
> +	system_state = SYSTEM_RUNNING;
>  	local_irq_enable();
>  
>   Enable_cpus:
> @@ -563,6 +568,7 @@ int hibernation_platform_enter(void)
>  		goto Enable_cpus;
>  
>  	local_irq_disable();
> +	system_state = SYSTEM_SUSPEND;
>  	syscore_suspend();
>  	if (pm_wakeup_pending()) {
>  		error = -EAGAIN;
> @@ -575,6 +581,7 @@ int hibernation_platform_enter(void)
>  
>   Power_up:
>  	syscore_resume();
> +	system_state = SYSTEM_RUNNING;
>  	local_irq_enable();
>  
>   Enable_cpus:
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 4c10be0f4843..5149c77506b3 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -428,6 +428,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
>  	arch_suspend_disable_irqs();
>  	BUG_ON(!irqs_disabled());
>  
> +	system_state = SYSTEM_SUSPEND;
> +
>  	error = syscore_suspend();
>  	if (!error) {
>  		*wakeup = pm_wakeup_pending();
> @@ -443,6 +445,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
>  		syscore_resume();
>  	}
>  
> +	system_state = SYSTEM_RUNNING;
> +
>  	arch_suspend_enable_irqs();
>  	BUG_ON(irqs_disabled());
>  
> diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
> index 49edc1c4f3e6..14de3727b18e 100644
> --- a/kernel/time/tick-common.c
> +++ b/kernel/time/tick-common.c
> @@ -490,6 +490,7 @@ void tick_freeze(void)
>  	if (tick_freeze_depth == num_online_cpus()) {
>  		trace_suspend_resume(TPS("timekeeping_freeze"),
>  				     smp_processor_id(), true);
> +		system_state = SYSTEM_SUSPEND;
>  		timekeeping_suspend();
>  	} else {
>  		tick_suspend_local();
> @@ -513,6 +514,7 @@ void tick_unfreeze(void)
>  
>  	if (tick_freeze_depth == num_online_cpus()) {
>  		timekeeping_resume();
> +		system_state = SYSTEM_RUNNING;
>  		trace_suspend_resume(TPS("timekeeping_freeze"),
>  				     smp_processor_id(), false);
>  	} else {
> 

Applied along with the rest of the series, thanks!