On 01/23/2014 12:41 PM, Len Brown wrote:
> From: Len Brown <len.br...@intel.com>
>
> Linux suspend-to-RAM was unreliable when first developed,
> and so sys_sync() was invoked inside the kernel at the
> start of every suspend flow.
>
> Today, many devices are invoking suspend with
> high reliability and high frequency, and they don't
> want to be forced to pay for sync on every suspend.
>
> So here we make it optional.
> De-select CONFIG_PM_SLEEP_SYNC to delete the call entirely.
> or keep CONFIG_PM_SLEEP and you can now clear the
> sys/power/sleep_sync attribte to disable the sync
> from user-space.
>
> As we have had this call for a long time,
> the default remains to keep the call, and to
> invoke it on every suspend.
>
> Signed-off-by: Len Brown <len.br...@intel.com>
> ---
> kernel/power/Kconfig | 8 ++++++++
> kernel/power/main.c | 33 +++++++++++++++++++++++++++++++++
> kernel/power/power.h | 1 +
> kernel/power/suspend.c | 10 +++++++---
> 4 files changed, 49 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 2fac9cc..d2927ce 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -102,6 +102,14 @@ config PM_SLEEP_SMP
> depends on PM_SLEEP
> select HOTPLUG_CPU
>
> +config PM_SLEEP_SYNC
How about naming it as PM_SLEEP_FS_SYNC (and similarly in the sysfs files
and variable names as well). Just to avoid confusion with "synchronous/async".
Regards,
Srivatsa S. Bhat
> + bool "Suspend to RAM starts with in-kernel call to sync()"
> + default y
> + depends on PM_SLEEP
> + ---help---
> + Build a call to sync() into the Linux kernel suspend to RAM flow.
> + The sync can still be skipped by clearing /sys/power/sleep_sync.
> +
> config PM_AUTOSLEEP
> bool "Opportunistic sleep"
> depends on PM_SLEEP
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index 1d1bf63..1102871 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -71,6 +71,36 @@ static ssize_t pm_async_store(struct kobject *kobj, struct
> kobj_attribute *attr,
>
> power_attr(pm_async);
>
> +#ifdef CONFIG_PM_SLEEP_SYNC
> +
> +/* If set, sync file systems at start of suspend flow */
> +int pm_sleep_sync_enabled = 1;
> +
> +static ssize_t pm_sleep_sync_show(struct kobject *kobj, struct
> kobj_attribute *attr,
> + char *buf)
> +{
> + return sprintf(buf, "%d\n", pm_sleep_sync_enabled);
> +}
> +
> +static ssize_t pm_sleep_sync_store(struct kobject *kobj, struct
> kobj_attribute *attr,
> + const char *buf, size_t n)
> +{
> + unsigned long val;
> +
> + if (kstrtoul(buf, 10, &val))
> + return -EINVAL;
> +
> + if (val > 1)
> + return -EINVAL;
> +
> + pm_sleep_sync_enabled = val;
> + return n;
> +}
> +
> +power_attr(pm_sleep_sync);
> +
> +#endif /* CONFIG_PM_SLEEP_SYNC */
> +
> #ifdef CONFIG_PM_DEBUG
> int pm_test_level = TEST_NONE;
>
> @@ -592,6 +622,9 @@ static struct attribute * g[] = {
> #ifdef CONFIG_PM_SLEEP
> &pm_async_attr.attr,
> &wakeup_count_attr.attr,
> +#ifdef CONFIG_PM_SLEEP_SYNC
> + &pm_sleep_sync_attr.attr,
> +#endif
> #ifdef CONFIG_PM_AUTOSLEEP
> &autosleep_attr.attr,
> #endif
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 7d4b7ff..dca60a7 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -200,6 +200,7 @@ static inline void suspend_test_finish(const char *label)
> {}
> #ifdef CONFIG_PM_SLEEP
> /* kernel/power/main.c */
> extern int pm_notifier_call_chain(unsigned long val);
> +extern int pm_sleep_sync_enabled;
> #endif
>
> #ifdef CONFIG_HIGHMEM
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 62ee437..2fb2f51 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -333,9 +333,13 @@ static int enter_state(suspend_state_t state)
> if (state == PM_SUSPEND_FREEZE)
> freeze_begin();
>
> - printk(KERN_INFO "PM: Syncing filesystems ... ");
> - sys_sync();
> - printk("done.\n");
> +#ifdef CONFIG_PM_SLEEP_SYNC
> + if (pm_sleep_sync_enabled) {
> + printk(KERN_INFO "PM: Syncing filesystems ... ");
> + sys_sync();
> + printk("done.\n");
> + }
> +#endif /* CONFIG_PM_SLEEP_SYNC */
>
> pr_debug("PM: Preparing system for %s sleep\n", pm_states[state]);
> error = suspend_prepare(state);
>
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