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Date: Fri, 12 Apr 2013 20:56:10 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Sam Ravnborg <sam@...nborg.org>
cc: David Miller <davem@...emloft.net>,
srivatsa.bhat@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, torvalds@...ux-foundation.org,
akpm@...ux-foundation.org, rusty@...tcorp.com.au,
paulmck@...ux.vnet.ibm.com, mingo@...e.hu, peterz@...radead.org,
magnus.damm@...il.com
Subject: Re: [PATCH v2] sparc: Use generic idle loop
On Thu, 11 Apr 2013, Sam Ravnborg wrote:
> Add generic cpu_idle support
>
> sparc32:
> - replace call to cpu_idle() with cpu_startup_entry()
> - add arch_cpu_idle()
>
> sparc64:
> - smp_callin() now include cpu_startup_entry() call so we can
> skip calling cpu_idle from assembler
> - add arch_cpu_idle() and arch_cpu_idle_dead()
Nice !
If Dave acks it, I'll pick it up
Thanks,
tglx
> Signed-off-by: Sam Ravnborg <sam@...nborg.org>
> Reviewed-by: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
> Cc: David S. Miller <davem@...emloft.net>
> ---
> v1->v2:
> - simplified arch_cpu_idle() - former sparc64_yield() based on comments from Srivatsa
> - dropped TIF_POLLING_NRFLAG handling
> - dropped smp_mb__after_clear_bit() - this is done in generic code using rmb()
> - dropped the out-most while (!need_resched() && !cpu_is_offline(cpu))
> - always enable irq on exit in arch_cpu_idle (both sparc32 and sparc64)
> - added comment from davem why we need to clear IE bit in sparc64 arch_cpu_idle()
>
> Sam
>
>
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 3d361f2..ee5eacc 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -37,6 +37,7 @@ config SPARC
> select GENERIC_SMP_IDLE_THREAD
> select GENERIC_CMOS_UPDATE
> select GENERIC_CLOCKEVENTS
> + select GENERIC_IDLE_LOOP
> select GENERIC_STRNCPY_FROM_USER
> select GENERIC_STRNLEN_USER
> select MODULES_USE_ELF_RELA
> diff --git a/arch/sparc/kernel/hvtramp.S b/arch/sparc/kernel/hvtramp.S
> index 9365432..605c960 100644
> --- a/arch/sparc/kernel/hvtramp.S
> +++ b/arch/sparc/kernel/hvtramp.S
> @@ -128,8 +128,7 @@ hv_cpu_startup:
>
> call smp_callin
> nop
> - call cpu_idle
> - mov 0, %o0
> +
> call cpu_panic
> nop
>
> diff --git a/arch/sparc/kernel/process_32.c b/arch/sparc/kernel/process_32.c
> index 62eede1..c852410 100644
> --- a/arch/sparc/kernel/process_32.c
> +++ b/arch/sparc/kernel/process_32.c
> @@ -64,23 +64,12 @@ extern void fpsave(unsigned long *, unsigned long *, void *, unsigned long *);
> struct task_struct *last_task_used_math = NULL;
> struct thread_info *current_set[NR_CPUS];
>
> -/*
> - * the idle loop on a Sparc... ;)
> - */
> -void cpu_idle(void)
> +/* Idle loop support. */
> +void arch_cpu_idle(void)
> {
> - set_thread_flag(TIF_POLLING_NRFLAG);
> -
> - /* endless idle loop with no priority at all */
> - for (;;) {
> - while (!need_resched()) {
> - if (sparc_idle)
> - (*sparc_idle)();
> - else
> - cpu_relax();
> - }
> - schedule_preempt_disabled();
> - }
> + if (sparc_idle)
> + (*sparc_idle)();
> + local_irq_enable();
> }
>
> /* XXX cli/sti -> local_irq_xxx here, check this works once SMP is fixed. */
> diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c
> index cdb80b2..9fbf0d1 100644
> --- a/arch/sparc/kernel/process_64.c
> +++ b/arch/sparc/kernel/process_64.c
> @@ -52,20 +52,17 @@
>
> #include "kstack.h"
>
> -static void sparc64_yield(int cpu)
> +/* Idle loop support on sparc64. */
> +void arch_cpu_idle(void)
> {
> if (tlb_type != hypervisor) {
> touch_nmi_watchdog();
> - return;
> - }
> -
> - clear_thread_flag(TIF_POLLING_NRFLAG);
> - smp_mb__after_clear_bit();
> -
> - while (!need_resched() && !cpu_is_offline(cpu)) {
> + } else {
> unsigned long pstate;
>
> - /* Disable interrupts. */
> + /* The sun4v sleeping code requires that we have PSTATE.IE cleared over
> + * the cpu sleep hypervisor call.
> + */
> __asm__ __volatile__(
> "rdpr %%pstate, %0\n\t"
> "andn %0, %1, %0\n\t"
> @@ -73,7 +70,7 @@ static void sparc64_yield(int cpu)
> : "=&r" (pstate)
> : "i" (PSTATE_IE));
>
> - if (!need_resched() && !cpu_is_offline(cpu))
> + if (!need_resched() && !cpu_is_offline(smp_processor_id()))
> sun4v_cpu_yield();
>
> /* Re-enable interrupts. */
> @@ -84,36 +81,16 @@ static void sparc64_yield(int cpu)
> : "=&r" (pstate)
> : "i" (PSTATE_IE));
> }
> -
> - set_thread_flag(TIF_POLLING_NRFLAG);
> + local_irq_enable();
> }
>
> -/* The idle loop on sparc64. */
> -void cpu_idle(void)
> -{
> - int cpu = smp_processor_id();
> -
> - set_thread_flag(TIF_POLLING_NRFLAG);
> -
> - while(1) {
> - tick_nohz_idle_enter();
> - rcu_idle_enter();
> -
> - while (!need_resched() && !cpu_is_offline(cpu))
> - sparc64_yield(cpu);
> -
> - rcu_idle_exit();
> - tick_nohz_idle_exit();
> -
> #ifdef CONFIG_HOTPLUG_CPU
> - if (cpu_is_offline(cpu)) {
> - sched_preempt_enable_no_resched();
> - cpu_play_dead();
> - }
> -#endif
> - schedule_preempt_disabled();
> - }
> +void arch_cpu_idle_dead()
> +{
> + sched_preempt_enable_no_resched();
> + cpu_play_dead();
> }
> +#endif
>
> #ifdef CONFIG_COMPAT
> static void show_regwindow32(struct pt_regs *regs)
> diff --git a/arch/sparc/kernel/smp_32.c b/arch/sparc/kernel/smp_32.c
> index 9e7e6d7..e3f2b81 100644
> --- a/arch/sparc/kernel/smp_32.c
> +++ b/arch/sparc/kernel/smp_32.c
> @@ -369,7 +369,7 @@ void __cpuinit sparc_start_secondary(void *arg)
> local_irq_enable();
>
> wmb();
> - cpu_idle();
> + cpu_startup_entry(CPUHP_ONLINE);
>
> /* We should never reach here! */
> BUG();
> diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
> index 537eb66..c025ffc 100644
> --- a/arch/sparc/kernel/smp_64.c
> +++ b/arch/sparc/kernel/smp_64.c
> @@ -127,6 +127,8 @@ void __cpuinit smp_callin(void)
>
> /* idle thread is expected to have preempt disabled */
> preempt_disable();
> +
> + cpu_startup_entry(CPUHP_ONLINE);
> }
>
> void cpu_panic(void)
> diff --git a/arch/sparc/kernel/trampoline_64.S b/arch/sparc/kernel/trampoline_64.S
> index da1b781..2e973a2 100644
> --- a/arch/sparc/kernel/trampoline_64.S
> +++ b/arch/sparc/kernel/trampoline_64.S
> @@ -407,8 +407,7 @@ after_lock_tlb:
>
> call smp_callin
> nop
> - call cpu_idle
> - mov 0, %o0
> +
> call cpu_panic
> nop
> 1: b,a,pt %xcc, 1b
>
--
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