Commit 7ded4291 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman

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: default avatarVaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 624e46d0
...@@ -59,14 +59,21 @@ static int snooze_loop(struct cpuidle_device *dev, ...@@ -59,14 +59,21 @@ static int snooze_loop(struct cpuidle_device *dev,
ppc64_runlatch_off(); ppc64_runlatch_off();
HMT_very_low(); HMT_very_low();
while (!need_resched()) { 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; break;
} }
}
HMT_medium(); HMT_medium();
ppc64_runlatch_on(); ppc64_runlatch_on();
clear_thread_flag(TIF_POLLING_NRFLAG); clear_thread_flag(TIF_POLLING_NRFLAG);
smp_mb();
return index; return index;
} }
......
...@@ -71,13 +71,20 @@ static int snooze_loop(struct cpuidle_device *dev, ...@@ -71,13 +71,20 @@ static int snooze_loop(struct cpuidle_device *dev,
while (!need_resched()) { while (!need_resched()) {
HMT_low(); HMT_low();
HMT_very_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; break;
} }
}
HMT_medium(); HMT_medium();
clear_thread_flag(TIF_POLLING_NRFLAG); clear_thread_flag(TIF_POLLING_NRFLAG);
smp_mb();
idle_loop_epilog(in_purr); idle_loop_epilog(in_purr);
......
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