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Commit 2fd77fff authored by Len Brown's avatar Len Brown Committed by Rafael J. Wysocki
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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: default avatarLen Brown <len.brown@intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 019d8817

kernel/power/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -18,6 +18,16 @@ config SUSPEND_FREEZER 


	  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

kernel/power/suspend.c

+2 −0
Original line number Diff line number Diff line
@@ -484,11 +484,13 @@ static int enter_state(suspend_state_t state) 
	if (state == PM_SUSPEND_FREEZE)

		freeze_begin();



#ifndef CONFIG_SUSPEND_SKIP_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);

#endif



	pr_debug("PM: Preparing system for sleep (%s)\n", pm_states[state]);

	error = suspend_prepare(state);