On Wed, Nov 20, 2013 at 11:28:03AM +0100, Peter Zijlstra wrote: > On Tue, Nov 19, 2013 at 01:06:30PM -0800, Jacob Pan wrote: > > I applied this patch on top of upstream kernel (801a760) and found out > > my machine completely failed to enter idle when nothing is running. > > turbostate shows 100% C0. ftrace shows kernel coming in and out of idle > > frequently. > > > > Both ACPI idle and intel_idle behaves the same way. I have to do the > > following change to allow entering C-states again. > That doesn't make any sense; current_set_polling_and_test() returns the > same thing need_resched() does. > > But you're right, intel_idle resides 100% in C0 and acpi_idle has 100% > C1 residency... most weird. So pretty silly actually; you cannot do a store (any store) in between monitor and mwait. The below version seems to work properly again with both acpi_idle and intel_idle. Now to go make that preempt_disable_no_resched cleanup compile.. :-) --- Subject: x86, acpi, idle: Restructure the mwait idle routines From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Date: Tue, 19 Nov 2013 12:31:53 +0100 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. Cc: arjan@xxxxxxxxxxxxxxx Cc: jacob.jun.pan@xxxxxxxxxxxxxxx Cc: Mike Galbraith <bitbucket@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: hpa@xxxxxxxxx Cc: lenb@xxxxxxxxxx Cc: shaohua.li@xxxxxxxxx Cc: rui.zhang@xxxxxxxxx Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> --- arch/x86/include/asm/mwait.h | 40 +++++++++++++++++++++++++++++++++++++ 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, 43 insertions(+), 75 deletions(-) --- 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 +15,42 @@ #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 (!current_set_polling_and_test()) { + if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR)) + clflush((void *)¤t_thread_info()->flags); + + __monitor((void *)¤t_thread_info()->flags, 0, 0); + if (!need_resched()) + __mwait(eax, ecx); + } + __current_clr_polling(); +} + #endif /* _ASM_X86_MWAIT_H */ --- 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); --- a/arch/x86/kernel/acpi/cstate.c +++ b/arch/x86/kernel/acpi/cstate.c @@ -150,29 +150,6 @@ int acpi_processor_ffh_cstate_probe(unsi } 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(); --- a/drivers/acpi/acpi_pad.c +++ b/drivers/acpi/acpi_pad.c @@ -193,10 +193,7 @@ static int power_saving_thread(void *dat 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) --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -727,11 +727,6 @@ static int acpi_idle_enter_c1(struct cpu 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 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 cpu } } - 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: */ --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -359,13 +359,7 @@ static int intel_idle(struct cpuidle_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); --- 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); } -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html