linux-kernel - [PATCH v5 1/3] x86/apic: Move pending intr check code into it's own function

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Message-ID: <20180301055930.2396-2-douly.fnst@cn.fujitsu.com>
Date:   Thu, 1 Mar 2018 13:59:28 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <tglx@...utronix.de>, <mingo@...nel.org>, <ebiederm@...ssion.com>,
        <bhe@...hat.com>, <andy.shevchenko@...il.com>,
        Dou Liyang <douly.fnst@...fujitsu.com>
Subject: [PATCH v5 1/3] x86/apic: Move pending intr check code into it's own function

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().

Signed-off-by: Dou Liyang <douly.fnst@...fujitsu.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
---
changelog:
 v4 --> v5:
  - Fix undeclared 'i' error reported by LKP

 arch/x86/kernel/apic/apic.c | 100 ++++++++++++++++++++++++--------------------
 1 file changed, 55 insertions(+), 45 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 2ceac9f6c5d7..69d2936e3154 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 +1467,11 @@ 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;
+	unsigned int value;
+#ifdef CONFIG_X86_32
+	int i;
+#endif
 
-	if (boot_cpu_has(X86_FEATURE_TSC))
-		tsc = rdtsc();
 
 	if (disable_apic) {
 		disable_ioapic_support();
@@ -1475,45 +1523,7 @@ 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