From: Len Brown <len.br...@intel.com>
The Linux kernel suspend path has traditionally invoked sys_sync().
But sys_sync() can be expensive, and some systems do not want
to pay the cost of sys_sync() on every suspend.
So make sys_sync on suspend optional.
Create sysfs attribute /sys/power/pm_suspend_do_sync.
When set to 1, the kernel will sys_sync() on suspend,
When set to 0, it will not.
This attribute can be changed by root at run-time.
Kernel build parameter CONFIG_PM_SUSPEND_DO_SYNC_DEFAULT.
As this is 1, by default, this patch does not change
default behavior.
Signed-off-by: Len Brown <len.br...@intel.com>
---
Documentation/ABI/testing/sysfs-power | 10 ++++++++++
kernel/power/Kconfig | 10 ++++++++++
kernel/power/main.c | 31 +++++++++++++++++++++++++++++++
kernel/power/power.h | 1 +
kernel/power/suspend.c | 12 +++++++-----
5 files changed, 59 insertions(+), 5 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-power
b/Documentation/ABI/testing/sysfs-power
index f455181..37df98d 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -256,3 +256,13 @@ Description:
Writing a "1" enables this printing while writing a "0"
disables it. The default value is "0". Reading from this file
will display the current value.
+
+What: /sys/power/pm_suspend_do_sync
+Date: July, 2015
+Contact: Len Brown <len.br...@intel.com>
+Description:
+ The /sys/power/pm_suspend_do_sync file controls whether the
kernel
+ will invoke sys_sync() on entry to the suspend to RAM path.
+ Yes if 1, no if 0. The default is set by build option
+ CONFIG_PM_SUSPEND_DO_SYNC_DEFAULT.
+
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 7e01f78..28976ed 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -103,6 +103,16 @@ config PM_SLEEP_SMP
depends on PM_SLEEP
select HOTPLUG_CPU
+config PM_SUSPEND_DO_SYNC_DEFAULT
+ int "Default value for /sys/power/suspend_do_sync"
+ range 0 1
+ default "1"
+ depends on SUSPEND
+ ---help---
+ Set default value for /sys/power/suspend_sync,
+ which controls whether kernel invokes sys_sync() on suspend to RAM.
+ Value 1 will do the sys_sync(), 0 will not.
+
config PM_AUTOSLEEP
bool "Opportunistic sleep"
depends on PM_SLEEP
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 86e8157..a16d369 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -71,6 +71,34 @@ static ssize_t pm_async_store(struct kobject *kobj, struct
kobj_attribute *attr,
power_attr(pm_async);
+#ifdef CONFIG_SUSPEND
+/* Execute sys_sync() in suspend to RAM path */
+int pm_suspend_do_sync = CONFIG_PM_SUSPEND_DO_SYNC_DEFAULT;
+
+static ssize_t pm_suspend_do_sync_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", pm_suspend_do_sync);
+}
+
+static ssize_t pm_suspend_do_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_suspend_do_sync = val;
+ return n;
+}
+
+power_attr(pm_suspend_do_sync);
+#endif
+
#ifdef CONFIG_PM_DEBUG
int pm_test_level = TEST_NONE;
@@ -592,6 +620,9 @@ static struct attribute * g[] = {
#ifdef CONFIG_PM_SLEEP
&pm_async_attr.attr,
&wakeup_count_attr.attr,
+#ifdef CONFIG_SUSPEND
+ &pm_suspend_do_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 ce9b832..a6120b9 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -201,6 +201,7 @@ 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_suspend_do_sync;
#endif
#ifdef CONFIG_HIGHMEM
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 8d7a1ef..aab5dca 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -482,11 +482,13 @@ static int enter_state(suspend_state_t state)
if (state == PM_SUSPEND_FREEZE)
freeze_begin();
- trace_suspend_resume(TPS("sync_filesystems"), 0, true);
- printk(KERN_INFO "PM: Syncing filesystems ... ");
- sys_sync();
- printk("done.\n");
- trace_suspend_resume(TPS("sync_filesystems"), 0, false);
+ if (pm_suspend_do_sync) {
+ trace_suspend_resume(TPS("sync_filesystems"), 0, true);
+ printk(KERN_INFO "PM: Syncing filesystems ... ");
+ sys_sync();
+ printk("done.\n");
+ trace_suspend_resume(TPS("sync_filesystems"), 0, false);
+ }
pr_debug("PM: Preparing system for %s sleep\n", pm_states[state]);
error = suspend_prepare(state);
--
2.4.1.314.g9532ead
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