PM / suspend: make sync() on suspend-to-RAM build-time optional
The Linux kernel suspend path has traditionally invoked sys_sync()
before freezing user threads.
But sys_sync() can be expensive, and some user-space OS's do not want
the kernel to pay the cost of sys_sync() on every suspend -- preferring
invoke sync() from user-space if/when they want it.
So make sys_sync on suspend build-time optional.
The default is unchanged.
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 9e30231..02e8dfa 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -18,6 +18,16 @@
Turning OFF this setting is NOT recommended! If in doubt, say Y.
+config SUSPEND_SKIP_SYNC
+ bool "Skip kernel's sys_sync() on suspend to RAM/standby"
+ depends on SUSPEND
+ depends on EXPERT
+ help
+ 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.
+
config HIBERNATE_CALLBACKS
bool