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From:   Frederic Weisbecker <frederic@kernel.org>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     Frederic Weisbecker <frederic@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Anna-Maria Behnsen <anna-maria@linutronix.de>
Subject: [PATCH 09/10] x86: Remove the current_clr_polling() call upon mwait exit
Date:   Fri, 11 Aug 2023 19:00:48 +0200
Message-Id: <20230811170049.308866-10-frederic@kernel.org>
In-Reply-To: <20230811170049.308866-1-frederic@kernel.org>
References: <20230811170049.308866-1-frederic@kernel.org>
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mwait_idle_with_hints() is mostly called from cpuidle which already sets
back TIF_NR_POLLING and fold TIF_NEED_RESCHED if necessary.

The only non-cpuidle caller is power_saving_thread() which acts as an idle
loop and is the only reason why mwait_idle_with_hints() carries a costly
fully ordered atomic operation upon idle exit.

Make this overhead proper to power_saving_thread() instead which already
duplicates quite some cpuidle code.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 arch/x86/include/asm/mwait.h | 1 -
 drivers/acpi/acpi_pad.c      | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 920426d691ce..c1be3775b94a 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -134,7 +134,6 @@ static __always_inline void mwait_idle_with_hints(unsigned long eax, unsigned lo
 			}
 		}
 	}
-	current_clr_polling();
 }
 
 /*
diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
index 7a453c5ff303..5a44afafe185 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -174,6 +174,7 @@ static int power_saving_thread(void *data)
 			stop_critical_timings();
 
 			mwait_idle_with_hints(power_saving_mwait_eax, 1);
+			current_clr_polling();
 
 			start_critical_timings();
 			tick_broadcast_exit();
-- 
2.34.1