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Message-Id: <1707982910-27680-8-git-send-email-mihai.carabas@oracle.com>
Date: Thu, 15 Feb 2024 09:41:49 +0200
From: Mihai Carabas <mihai.carabas@...cle.com>
To: linux-arm-kernel@...ts.infradead.org
Cc: kvm@...r.kernel.org, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, catalin.marinas@....com, will@...nel.org,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
hpa@...or.com, pbonzini@...hat.com, wanpengli@...cent.com,
vkuznets@...hat.com, rafael@...nel.org, daniel.lezcano@...aro.org,
akpm@...ux-foundation.org, pmladek@...e.com, peterz@...radead.org,
dianders@...omium.org, npiggin@...il.com, rick.p.edgecombe@...el.com,
joao.m.martins@...cle.com, juerg.haefliger@...onical.com,
mic@...ikod.net, mihai.carabas@...cle.com, arnd@...db.de,
ankur.a.arora@...cle.com
Subject: [PATCH v4 7/8] cpuidle/poll_state: replace cpu_relax with smp_cond_load_relaxed
cpu_relax on ARM64 does a simple "yield". Thus we replace it with
smp_cond_load_relaxed which basically does a "wfe".
Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Mihai Carabas <mihai.carabas@...cle.com>
---
drivers/cpuidle/poll_state.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/drivers/cpuidle/poll_state.c b/drivers/cpuidle/poll_state.c
index 9b6d90a72601..1e45be906e72 100644
--- a/drivers/cpuidle/poll_state.c
+++ b/drivers/cpuidle/poll_state.c
@@ -13,6 +13,7 @@
static int __cpuidle poll_idle(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index)
{
+ unsigned long ret;
u64 time_start;
time_start = local_clock_noinstr();
@@ -26,12 +27,16 @@ static int __cpuidle poll_idle(struct cpuidle_device *dev,
limit = cpuidle_poll_time(drv, dev);
- while (!need_resched()) {
- cpu_relax();
- if (loop_count++ < POLL_IDLE_RELAX_COUNT)
- continue;
-
+ for (;;) {
loop_count = 0;
+
+ ret = smp_cond_load_relaxed(¤t_thread_info()->flags,
+ VAL & _TIF_NEED_RESCHED ||
+ loop_count++ >= POLL_IDLE_RELAX_COUNT);
+
+ if (!(ret & _TIF_NEED_RESCHED))
+ break;
+
if (local_clock_noinstr() - time_start > limit) {
dev->poll_time_limit = true;
break;
--
1.8.3.1
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