[PATCH 11/14] powerpc/64s: idle no memory barrier after break from idle
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2017-06-02 07:40:34
Subsystem:
cpu idle time management framework, the rest · Maintainers:
"Rafael J. Wysocki", Daniel Lezcano, Linus Torvalds
A memory barrier is not required after the task wakes up, only if we clear the polling flag before waking. The case where we have work to do is the important one, so optimise for it. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- drivers/cpuidle/cpuidle-powernv.c | 11 +++++++++-- drivers/cpuidle/cpuidle-pseries.c | 11 +++++++++-- 2 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index f0247652d91f..c53a8bb40471 100644
--- a/drivers/cpuidle/cpuidle-powernv.c
+++ b/drivers/cpuidle/cpuidle-powernv.c@@ -59,14 +59,21 @@ static int snooze_loop(struct cpuidle_device *dev, ppc64_runlatch_off(); HMT_very_low(); while (!need_resched()) { - if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) + if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) { + /* + * Task has not woken up but we are exiting the polling + * loop anyway. Require a barrier after polling is + * cleared to order subsequent test of need_resched(). + */ + clear_thread_flag(TIF_POLLING_NRFLAG); + smp_mb(); break; + } } HMT_medium(); ppc64_runlatch_on(); clear_thread_flag(TIF_POLLING_NRFLAG); - smp_mb(); return index; }
diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c
index a404f352d284..e9b3853d93ea 100644
--- a/drivers/cpuidle/cpuidle-pseries.c
+++ b/drivers/cpuidle/cpuidle-pseries.c@@ -71,13 +71,20 @@ static int snooze_loop(struct cpuidle_device *dev, while (!need_resched()) { HMT_low(); HMT_very_low(); - if (snooze_timeout_en && get_tb() > snooze_exit_time) + if (likely(snooze_timeout_en) && get_tb() > snooze_exit_time) { + /* + * Task has not woken up but we are exiting the polling + * loop anyway. Require a barrier after polling is + * cleared to order subsequent test of need_resched(). + */ + clear_thread_flag(TIF_POLLING_NRFLAG); + smp_mb(); break; + } } HMT_medium(); clear_thread_flag(TIF_POLLING_NRFLAG); - smp_mb(); idle_loop_epilog(in_purr);
--
2.11.0