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authorLen Brown <len.brown@intel.com>2015-07-31 12:46:17 -0400
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-07-31 23:46:05 +0200
commit2fd77fff4b440c29b48c31db0ce2aec7d319959f (patch)
treefe1c131b86a1cefe66e2ed2b7641b8c8db78c757 /kernel/power
parent019d8817b1b064c2bacfbcf40fc68184438ad05a (diff)
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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: Len Brown <len.brown@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'kernel/power')
-rw-r--r--kernel/power/Kconfig10
-rw-r--r--kernel/power/suspend.c2
2 files changed, 12 insertions, 0 deletions
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);