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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-02-12 23:33:15 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-02-13 23:49:36 +0100
commit3810631332465d967ba5e27ea2c7dff2c9afac6c (patch)
tree9000632cbf95f7d3f1e03640195708b3146c64dc /kernel/sched
parent18320f2a6871aaf2522f793fee4a67eccf5e131a (diff)
PM / sleep: Re-implement suspend-to-idle handling
In preparation for adding support for quiescing timers in the final stage of suspend-to-idle transitions, rework the freeze_enter() function making the system wait on a wakeup event, the freeze_wake() function terminating the suspend-to-idle loop and the mechanism by which deep idle states are entered during suspend-to-idle. First of all, introduce a simple state machine for suspend-to-idle and make the code in question use it. Second, prevent freeze_enter() from losing wakeup events due to race conditions and ensure that the number of online CPUs won't change while it is being executed. In addition to that, make it force all of the CPUs re-enter the idle loop in case they are in idle states already (so they can enter deeper idle states if possible). Next, drop cpuidle_use_deepest_state() and replace use_deepest_state checks in cpuidle_select() and cpuidle_reflect() with a single suspend-to-idle state check in cpuidle_idle_call(). Finally, introduce cpuidle_enter_freeze() that will simply find the deepest idle state available to the given CPU and enter it using cpuidle_enter(). Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/idle.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index aaf1c1d5cf5d..94b2d7b88a27 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -7,6 +7,7 @@
#include <linux/tick.h>
#include <linux/mm.h>
#include <linux/stackprotector.h>
+#include <linux/suspend.h>
#include <asm/tlb.h>
@@ -105,6 +106,21 @@ static void cpuidle_idle_call(void)
rcu_idle_enter();
/*
+ * Suspend-to-idle ("freeze") is a system state in which all user space
+ * has been frozen, all I/O devices have been suspended and the only
+ * activity happens here and in iterrupts (if any). In that case bypass
+ * the cpuidle governor and go stratight for the deepest idle state
+ * available. Possibly also suspend the local tick and the entire
+ * timekeeping to prevent timer interrupts from kicking us out of idle
+ * until a proper wakeup interrupt happens.
+ */
+ if (idle_should_freeze()) {
+ cpuidle_enter_freeze();
+ local_irq_enable();
+ goto exit_idle;
+ }
+
+ /*
* Ask the cpuidle framework to choose a convenient idle state.
* Fall back to the default arch idle method on errors.
*/