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authorNicholas Piggin <npiggin@gmail.com>2017-06-14 16:02:41 +0300
committerMichael Ellerman <mpe@ellerman.id.au>2017-06-28 06:08:12 +0300
commit7ded429152e84831f6696585755f318fb351e67f (patch)
treefa7aa9cf3c30c61ef5ec7a01cbc92be38da99815 /drivers/cpuidle
parent624e46d03576dd4d5667bad9d2ef814135d0075c (diff)
downloadlinux-7ded429152e84831f6696585755f318fb351e67f.tar.xz
cpuidle: powerpc: no memory barrier after break from idle
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. Reviewed-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'drivers/cpuidle')
-rw-r--r--drivers/cpuidle/cpuidle-powernv.c11
-rw-r--r--drivers/cpuidle/cpuidle-pseries.c11
2 files changed, 18 insertions, 4 deletions
diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
index 9d03326ac05e..37b0698b7193 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);