From 2fd77fff4b440c29b48c31db0ce2aec7d319959f Mon Sep 17 00:00:00 2001 From: Len Brown Date: Fri, 31 Jul 2015 12:46:17 -0400 Subject: [PATCH] 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 Signed-off-by: Rafael J. Wysocki --- kernel/power/Kconfig | 10 ++++++++++ kernel/power/suspend.c | 2 ++ 2 files changed, 12 insertions(+) diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index 9e302315e33d..02e8dfaa1ce2 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -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 diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c index 53266b729fd9..7e4cda4a8dd9 100644 --- a/kernel/power/suspend.c +++ b/kernel/power/suspend.c @@ -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); -- 2.20.1