[PATCH 4/4] x86: Remove the current_clr_polling() call upon mwait exit

Frederic Weisbecker
2023-11-15T15:14:22Z

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.

Acked-by: Rafael J. Wysocki <rafael@kernel.org>
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 bd1ad07f0290..86b57123713f 100644
--- a/drivers/acpi/acpi_pad.c
+++ b/drivers/acpi/acpi_pad.c
@@ -175,6 +175,7 @@ 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();
--
2.42.1