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Subject[PATCH 2/2] PM: CONFIG_SUSPEND_SKIP_SYNC sets default for, '/sys/power/sync_on_suspend'
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Slightly change the behaviour of build-time switch CONFIG_SUSPEND_SKIP_SYNC:
Make it configure the default for '/sys/power/sync_on_suspend', now that we
have a run-time switch for it.

Signed-off-by: Jonas Meurer <jonas@freesources.org>
---
Documentation/ABI/testing/sysfs-power | 7 ++++---
kernel/power/Kconfig | 5 ++++-
kernel/power/main.c | 2 +-
kernel/power/suspend.c | 2 +-
4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power
index f164a364e89a..783b3ce8eb06 100644
--- a/Documentation/ABI/testing/sysfs-power
+++ b/Documentation/ABI/testing/sysfs-power
@@ -418,6 +418,7 @@ Description:
aware that you have to take care of sync() yourself before
suspending the system if you disable it here.

- Writing a "1" (default) to this file enables the sync() and
- writing a "0" disables it. Reads from the file return the
- current value.
+ Writing a "1" to this file enables the sync() and writing a
+ "0" disables it. Reads from the file return the current value.
+ The default is "1" but can be configured with the build-time
+ config flag "SUSPEND_SKIP_SYNC".
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index d3667b4075c1..7cbfbeacd68a 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -27,7 +27,10 @@ config SUSPEND_SKIP_SYNC
Skip the kernel sys_sync() before freezing user processes.
Some systems prefer not to pay this cost on every invocation
of suspend, or they are content with invoking sync() from
- user-space before invoking suspend. Say Y if that's your case.
+ user-space before invoking suspend. There's a run-time switch
+ at '/sys/power/sync_on_suspend' to configure this behaviour.
+ This setting changes the default for the run-tim switch. Say Y
+ to change the default to disable the kernel sys_sync().

config HIBERNATE_CALLBACKS
bool
diff --git a/kernel/power/main.c b/kernel/power/main.c
index 7d9d579a8e6f..69b7a8aeca3b 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -197,7 +197,7 @@ power_attr(mem_sleep);
* show() returns whether ksys_sync_helper() is invoked before suspend.
* store() accepts 0 or 1. 0 disables ksys_sync_helper() and 1 enables it.
*/
-bool sync_on_suspend_enabled = true;
+bool sync_on_suspend_enabled = !IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC);

static ssize_t sync_on_suspend_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 503d56419a69..2c47280fbfc7 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -564,7 +564,7 @@ static int enter_state(suspend_state_t state)
if (state == PM_SUSPEND_TO_IDLE)
s2idle_begin();

- if (!IS_ENABLED(CONFIG_SUSPEND_SKIP_SYNC) && sync_on_suspend_enabled) {
+ if (sync_on_suspend_enabled) {
trace_suspend_resume(TPS("sync_filesystems"), 0, true);
ksys_sync_helper();
trace_suspend_resume(TPS("sync_filesystems"), 0, false);
--
2.20.1
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