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SubjectRe: [PATCH 1/1] x86: replace cpu_up hard-coded mdelay with variable
On Sat, Apr 18, 2015 at 8:53 PM, Len Brown <lenb@kernel.org> wrote:
> From: Len Brown <len.brown@intel.com>
>

[...]

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index b7d31ca..d2a91da 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -884,6 +884,21 @@ config SCHED_MC
> making when dealing with multi-core CPU chips at a cost of slightly
> increased overhead in some places. If unsure say N here.
>
> +config X86_INIT_MDELAY
> + int "Milliseconds to wait to de-assert INIT upon CPU startup" if SMP
> + range 0 10
> + default "10"
> + ---help---
> + This allows you to specify how long the BSP will delay
> + between asserting INIT and de-asserting INIT when starting another CPU.
> + This delay is paid on each cpu-online operation, including boot-time,
> + resume from suspend, and resume from hibernate. The the value of

Happened to notice a 2x "The the..." when I came across this in linux-next
today and was reading the help out of curiousity...

P.
--

> + 10 millisec was specified by Multi-Processor Spec 1.4 in 1997.
> + But modern hardware does not require any delay.
> +
> + The kernel boot-time parameter "cpu_init_mdelay="
> + will over-ride this build-time default.
> +
> source "kernel/Kconfig.preempt"
>
> config UP_LATE_INIT
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index febc6aa..973621f 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -555,6 +555,20 @@ wakeup_secondary_cpu_via_nmi(int apicid, unsigned long start_eip)
> return (send_status | accept_status);
> }
>
> +unsigned int x86_init_mdelay = CONFIG_X86_INIT_MDELAY;
> +static int __init cpu_init_mdelay(char *str)
> +{
> + unsigned int tmp;
> +
> + get_option(&str, &tmp);
> + pr_info("x86_init_mdelay set to %d, was %d", tmp, x86_init_mdelay);
> + x86_init_mdelay = tmp;
> + return 0;
> +}
> +
> +early_param("cpu_init_mdelay", cpu_init_mdelay);
> +
> +
> static int
> wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
> {
> @@ -586,7 +600,7 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
> pr_debug("Waiting for send to finish...\n");
> send_status = safe_apic_wait_icr_idle();
>
> - mdelay(10);
> + mdelay(x86_init_mdelay);
>
> pr_debug("Deasserting INIT\n");
>
> --
> 2.4.0.rc1
>
> --
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