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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2018-03-14 15:08:57 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2018-03-29 13:06:07 +0200
commita37b969a61c1efcd16da9c9ab3b237235c48560c (patch)
tree96880c97f214f89182d2ab022275fdd88c06dd81
parentbda4d21b6e5d423e3f21a6c49d3d5283592e3b65 (diff)
downloadblackbird-op-linux-a37b969a61c1efcd16da9c9ab3b237235c48560c.tar.gz
blackbird-op-linux-a37b969a61c1efcd16da9c9ab3b237235c48560c.zip
cpuidle: poll_state: Add time limit to poll_idle()
If poll_idle() is allowed to spin until need_resched() returns 'true', it may actually spin for a much longer time than expected by the idle governor, since set_tsk_need_resched() is not always called by the timer interrupt handler. If that happens, the CPU may spend much more time than anticipated in the "polling" state. To prevent that from happening, limit the time of the spinning loop in poll_idle(). Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Tested-by: Doug Smythies <dsmythies@telus.net>
-rw-r--r--drivers/cpuidle/poll_state.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/cpuidle/poll_state.c b/drivers/cpuidle/poll_state.c
index 7416b16287de..68cdc506524b 100644
--- a/drivers/cpuidle/poll_state.c
+++ b/drivers/cpuidle/poll_state.c
@@ -6,15 +6,24 @@
#include <linux/cpuidle.h>
#include <linux/sched.h>
+#include <linux/sched/clock.h>
#include <linux/sched/idle.h>
+#define POLL_IDLE_TIME_LIMIT (TICK_NSEC / 16)
+
static int __cpuidle poll_idle(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index)
{
+ u64 time_start = local_clock();
+
local_irq_enable();
if (!current_set_polling_and_test()) {
- while (!need_resched())
+ while (!need_resched()) {
cpu_relax();
+
+ if (local_clock() - time_start > POLL_IDLE_TIME_LIMIT)
+ break;
+ }
}
current_clr_polling();
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