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Date: Mon, 26 Feb 2018 16:52:21 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Dou Liyang <douly.fnst@...fujitsu.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>, ebiederm@...ssion.com,
Baoquan He <bhe@...hat.com>
Subject: Re: [PATCH v4 1/2] x86/apic: Move pending intr check code into it's
own function
On Mon, Feb 26, 2018 at 4:39 AM, Dou Liyang <douly.fnst@...fujitsu.com> wrote:
> the pending interrupt check code is mixed with the local APIC setup code,
> that looks messy.
>
> Extract the related code, move it into a new function named
> apic_pending_intr_clear().
FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
>
> Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
> ---
> arch/x86/kernel/apic/apic.c | 98 ++++++++++++++++++++++++---------------------
> 1 file changed, 52 insertions(+), 46 deletions(-)
>
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index 84b244ec49ed..be223ebd1bb3 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -1408,6 +1408,56 @@ static void lapic_setup_esr(void)
> oldvalue, value);
> }
>
> +static void apic_pending_intr_clear(void)
> +{
> + long long max_loops = cpu_khz ? cpu_khz : 1000000;
> + unsigned long long tsc = 0, ntsc;
> + unsigned int value, queued;
> + int i, j, acked = 0;
> +
> + if (boot_cpu_has(X86_FEATURE_TSC))
> + tsc = rdtsc();
> + /*
> + * After a crash, we no longer service the interrupts and a pending
> + * interrupt from previous kernel might still have ISR bit set.
> + *
> + * Most probably by now CPU has serviced that pending interrupt and
> + * it might not have done the ack_APIC_irq() because it thought,
> + * interrupt came from i8259 as ExtInt. LAPIC did not get EOI so it
> + * does not clear the ISR bit and cpu thinks it has already serivced
> + * the interrupt. Hence a vector might get locked. It was noticed
> + * for timer irq (vector 0x31). Issue an extra EOI to clear ISR.
> + */
> + do {
> + queued = 0;
> + for (i = APIC_ISR_NR - 1; i >= 0; i--)
> + queued |= apic_read(APIC_IRR + i*0x10);
> +
> + for (i = APIC_ISR_NR - 1; i >= 0; i--) {
> + value = apic_read(APIC_ISR + i*0x10);
> + for (j = 31; j >= 0; j--) {
> + if (value & (1<<j)) {
> + ack_APIC_irq();
> + acked++;
> + }
> + }
> + }
> + if (acked > 256) {
> + printk(KERN_ERR "LAPIC pending interrupts after %d EOI\n",
> + acked);
> + break;
> + }
> + if (queued) {
> + if (boot_cpu_has(X86_FEATURE_TSC) && cpu_khz) {
> + ntsc = rdtsc();
> + max_loops = (cpu_khz << 10) - (ntsc - tsc);
> + } else
> + max_loops--;
> + }
> + } while (queued && max_loops > 0);
> + WARN_ON(max_loops <= 0);
> +}
> +
> /**
> * setup_local_APIC - setup the local APIC
> *
> @@ -1417,13 +1467,7 @@ static void lapic_setup_esr(void)
> static void setup_local_APIC(void)
> {
> int cpu = smp_processor_id();
> - unsigned int value, queued;
> - int i, j, acked = 0;
> - unsigned long long tsc = 0, ntsc;
> - long long max_loops = cpu_khz ? cpu_khz : 1000000;
> -
> - if (boot_cpu_has(X86_FEATURE_TSC))
> - tsc = rdtsc();
> + unsigned int value;
>
> if (disable_apic) {
> disable_ioapic_support();
> @@ -1475,45 +1519,7 @@ static void setup_local_APIC(void)
> value &= ~APIC_TPRI_MASK;
> apic_write(APIC_TASKPRI, value);
>
> - /*
> - * After a crash, we no longer service the interrupts and a pending
> - * interrupt from previous kernel might still have ISR bit set.
> - *
> - * Most probably by now CPU has serviced that pending interrupt and
> - * it might not have done the ack_APIC_irq() because it thought,
> - * interrupt came from i8259 as ExtInt. LAPIC did not get EOI so it
> - * does not clear the ISR bit and cpu thinks it has already serivced
> - * the interrupt. Hence a vector might get locked. It was noticed
> - * for timer irq (vector 0x31). Issue an extra EOI to clear ISR.
> - */
> - do {
> - queued = 0;
> - for (i = APIC_ISR_NR - 1; i >= 0; i--)
> - queued |= apic_read(APIC_IRR + i*0x10);
> -
> - for (i = APIC_ISR_NR - 1; i >= 0; i--) {
> - value = apic_read(APIC_ISR + i*0x10);
> - for (j = 31; j >= 0; j--) {
> - if (value & (1<<j)) {
> - ack_APIC_irq();
> - acked++;
> - }
> - }
> - }
> - if (acked > 256) {
> - printk(KERN_ERR "LAPIC pending interrupts after %d EOI\n",
> - acked);
> - break;
> - }
> - if (queued) {
> - if (boot_cpu_has(X86_FEATURE_TSC) && cpu_khz) {
> - ntsc = rdtsc();
> - max_loops = (cpu_khz << 10) - (ntsc - tsc);
> - } else
> - max_loops--;
> - }
> - } while (queued && max_loops > 0);
> - WARN_ON(max_loops <= 0);
> + apic_pending_intr_clear();
>
> /*
> * Now that we are all set up, enable the APIC
> --
> 2.14.3
>
>
>
--
With Best Regards,
Andy Shevchenko
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