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Date: Tue, 19 Nov 2013 14:06:44 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Peter Zijlstra <peterz@...radead.org>
Cc: lenb@...nel.org, linux-acpi@...r.kernel.org,
linux-kernel@...r.kernel.org, shaohua.li@...el.com,
rui.zhang@...el.com, arjan@...ux.intel.com,
jacob.jun.pan@...ux.intel.com,
Mike Galbraith <bitbucket@...ine.de>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>, hpa@...or.com
Subject: Re: [PATCH] x86, acpi, idle: Restructure the mwait idle routines
On Tuesday, November 19, 2013 12:31:53 PM Peter Zijlstra wrote:
> People seem to delight in writing wrong and broken mwait idle routines;
> collapse the lot.
>
> This leaves mwait_play_dead() the sole remaining user of __mwait() and
> new __mwait() users are probably doing it wrong.
>
> Also remove __sti_mwait() as its unused.
>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
For the ACPI part:
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> Mike, does this cure your core2?
>
> arch/x86/include/asm/mwait.h | 42 ++++++++++++++++++++++++++++++++++++++
> arch/x86/include/asm/processor.h | 23 ---------------------
> arch/x86/kernel/acpi/cstate.c | 23 ---------------------
> drivers/acpi/acpi_pad.c | 5 +----
> drivers/acpi/processor_idle.c | 15 --------------
> drivers/idle/intel_idle.c | 8 +-------
> drivers/thermal/intel_powerclamp.c | 4 +---
> 7 files changed, 45 insertions(+), 75 deletions(-)
>
> diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
> index 2f366d0ac6b4..80014dade987 100644
> --- a/arch/x86/include/asm/mwait.h
> +++ b/arch/x86/include/asm/mwait.h
> @@ -1,6 +1,8 @@
> #ifndef _ASM_X86_MWAIT_H
> #define _ASM_X86_MWAIT_H
>
> +#include <linux/sched.h>
> +
> #define MWAIT_SUBSTATE_MASK 0xf
> #define MWAIT_CSTATE_MASK 0xf
> #define MWAIT_SUBSTATE_SIZE 4
> @@ -13,4 +15,44 @@
>
> #define MWAIT_ECX_INTERRUPT_BREAK 0x1
>
> +static inline void __monitor(const void *eax, unsigned long ecx,
> + unsigned long edx)
> +{
> + /* "monitor %eax, %ecx, %edx;" */
> + asm volatile(".byte 0x0f, 0x01, 0xc8;"
> + :: "a" (eax), "c" (ecx), "d"(edx));
> +}
> +
> +static inline void __mwait(unsigned long eax, unsigned long ecx)
> +{
> + /* "mwait %eax, %ecx;" */
> + asm volatile(".byte 0x0f, 0x01, 0xc9;"
> + :: "a" (eax), "c" (ecx));
> +}
> +
> +/*
> + * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
> + * which can obviate IPI to trigger checking of need_resched.
> + * We execute MONITOR against need_resched and enter optimized wait state
> + * through MWAIT. Whenever someone changes need_resched, we would be woken
> + * up from MWAIT (without an IPI).
> + *
> + * New with Core Duo processors, MWAIT can take some hints based on CPU
> + * capability.
> + */
> +static inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
> +{
> + if (need_resched())
> + return;
> +
> + if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
> + clflush((void *)¤t_thread_info()->flags);
> +
> + __monitor((void *)¤t_thread_info()->flags, 0, 0);
> + if (!current_set_polling_and_test())
> + __mwait(eax, ecx);
> +
> + __current_clr_polling();
> +}
> +
> #endif /* _ASM_X86_MWAIT_H */
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 7b034a4057f9..24821f5768bc 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -700,29 +700,6 @@ static inline void sync_core(void)
> #endif
> }
>
> -static inline void __monitor(const void *eax, unsigned long ecx,
> - unsigned long edx)
> -{
> - /* "monitor %eax, %ecx, %edx;" */
> - asm volatile(".byte 0x0f, 0x01, 0xc8;"
> - :: "a" (eax), "c" (ecx), "d"(edx));
> -}
> -
> -static inline void __mwait(unsigned long eax, unsigned long ecx)
> -{
> - /* "mwait %eax, %ecx;" */
> - asm volatile(".byte 0x0f, 0x01, 0xc9;"
> - :: "a" (eax), "c" (ecx));
> -}
> -
> -static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
> -{
> - trace_hardirqs_on();
> - /* "mwait %eax, %ecx;" */
> - asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
> - :: "a" (eax), "c" (ecx));
> -}
> -
> extern void select_idle_routine(const struct cpuinfo_x86 *c);
> extern void init_amd_e400_c1e_mask(void);
>
> diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
> index d2b7f27781bc..e69182fd01cf 100644
> --- a/arch/x86/kernel/acpi/cstate.c
> +++ b/arch/x86/kernel/acpi/cstate.c
> @@ -150,29 +150,6 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
> }
> EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);
>
> -/*
> - * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
> - * which can obviate IPI to trigger checking of need_resched.
> - * We execute MONITOR against need_resched and enter optimized wait state
> - * through MWAIT. Whenever someone changes need_resched, we would be woken
> - * up from MWAIT (without an IPI).
> - *
> - * New with Core Duo processors, MWAIT can take some hints based on CPU
> - * capability.
> - */
> -void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
> -{
> - if (!need_resched()) {
> - if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
> - clflush((void *)¤t_thread_info()->flags);
> -
> - __monitor((void *)¤t_thread_info()->flags, 0, 0);
> - smp_mb();
> - if (!need_resched())
> - __mwait(ax, cx);
> - }
> -}
> -
> void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
> {
> unsigned int cpu = smp_processor_id();
> diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
> index fc6008fbce35..509452a62f96 100644
> --- a/drivers/acpi/acpi_pad.c
> +++ b/drivers/acpi/acpi_pad.c
> @@ -193,10 +193,7 @@ static int power_saving_thread(void *data)
> CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
> stop_critical_timings();
>
> - __monitor((void *)¤t_thread_info()->flags, 0, 0);
> - smp_mb();
> - if (!need_resched())
> - __mwait(power_saving_mwait_eax, 1);
> + mwait_idle_with_hints(power_saving_mwait_eax, 1);
>
> start_critical_timings();
> if (lapic_marked_unstable)
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 644516d9bde6..f90c56c8379e 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -727,11 +727,6 @@ static int acpi_idle_enter_c1(struct cpuidle_device *dev,
> if (unlikely(!pr))
> return -EINVAL;
>
> - if (cx->entry_method == ACPI_CSTATE_FFH) {
> - if (current_set_polling_and_test())
> - return -EINVAL;
> - }
> -
> lapic_timer_state_broadcast(pr, cx, 1);
> acpi_idle_do_entry(cx);
>
> @@ -785,11 +780,6 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
> if (unlikely(!pr))
> return -EINVAL;
>
> - if (cx->entry_method == ACPI_CSTATE_FFH) {
> - if (current_set_polling_and_test())
> - return -EINVAL;
> - }
> -
> /*
> * Must be done before busmaster disable as we might need to
> * access HPET !
> @@ -841,11 +831,6 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
> }
> }
>
> - if (cx->entry_method == ACPI_CSTATE_FFH) {
> - if (current_set_polling_and_test())
> - return -EINVAL;
> - }
> -
> acpi_unlazy_tlb(smp_processor_id());
>
> /* Tell the scheduler that we are going deep-idle: */
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 3226ce98fb18..3b56d76a5bca 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -359,13 +359,7 @@ static int intel_idle(struct cpuidle_device *dev,
> if (!(lapic_timer_reliable_states & (1 << (cstate))))
> clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu);
>
> - if (!current_set_polling_and_test()) {
> -
> - __monitor((void *)¤t_thread_info()->flags, 0, 0);
> - smp_mb();
> - if (!need_resched())
> - __mwait(eax, ecx);
> - }
> + mwait_idle_with_hints(eax, ecx);
>
> if (!(lapic_timer_reliable_states & (1 << (cstate))))
> clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu);
> diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
> index 8f181b3f842b..e8275f2df9af 100644
> --- a/drivers/thermal/intel_powerclamp.c
> +++ b/drivers/thermal/intel_powerclamp.c
> @@ -438,9 +438,7 @@ static int clamp_thread(void *arg)
> */
> local_touch_nmi();
> stop_critical_timings();
> - __monitor((void *)¤t_thread_info()->flags, 0, 0);
> - cpu_relax(); /* allow HT sibling to run */
> - __mwait(eax, ecx);
> + mwait_idle_with_hints(eax, ecx);
> start_critical_timings();
> atomic_inc(&idle_wakeup_counter);
> }
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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