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    Subject[patch] 2.4.1, 2.4.2-pre3: APIC lockups
    Hi,

    After performing various tests I came to the following workaround for
    APIC lockups which people observe under IRQ load, mostly for networking
    stuff. I believe the test should work in all cases as it basically
    implements a manual replacement for EOI messages. In my simulated
    environment I was unable to get a lockup with the code in place, even
    though I was getting about every other level-triggered IRQ misdelivered.

    Please test it extensively, as much as you can, before I submit it for
    inclusion. If you ever get "Aieee!!! Remote IRR still set after unlock!"
    message, please report it to me immediately -- it means the code failed.
    There is also an additional debugging/statistics counter provided in
    /proc/cpuinfo that counts interrupts which got delivered with its trigger
    mode mismatched. Check it out to find if you get any misdelivered
    interrupts at all.

    The patch applies to 2.4.1 and 2.4.2-pre3 cleanly. For -ac series you
    need to revert patch-2.4.0-io_apic-2 first -- check list archives for the
    patch.

    Andrew, Manfred: that's a one-line-updated version comparing to what you
    already have.

    Ingo: while implementing irq_mis_count, I corrected irq_err_count to be
    atomic_t as well.

    Good luck,

    Maciej

    --
    + Maciej W. Rozycki, Technical University of Gdansk, Poland +
    +--------------------------------------------------------------+
    + e-mail: macro@ds2.pg.gda.pl, PGP key available +

    patch-2.4.1-io_apic-46
    diff -up --recursive --new-file linux-2.4.1.macro/arch/i386/kernel/apic.c linux-2.4.1/arch/i386/kernel/apic.c
    --- linux-2.4.1.macro/arch/i386/kernel/apic.c Wed Dec 13 23:54:27 2000
    +++ linux-2.4.1/arch/i386/kernel/apic.c Mon Feb 12 16:11:15 2001
    @@ -23,6 +23,7 @@
    #include <linux/mc146818rtc.h>
    #include <linux/kernel_stat.h>

    +#include <asm/atomic.h>
    #include <asm/smp.h>
    #include <asm/mtrr.h>
    #include <asm/mpspec.h>
    @@ -270,7 +271,13 @@ void __init setup_local_APIC (void)
    * PCI Ne2000 networking cards and PII/PIII processors, dual
    * BX chipset. ]
    */
    -#if 0
    + /*
    + * Actually disabling the focus CPU check just makes the hang less
    + * frequent as it makes the interrupt distributon model be more
    + * like LRU than MRU (the short-term load is more even across CPUs).
    + * See also the comment in end_level_ioapic_irq(). --macro
    + */
    +#if 1
    /* Enable focus processor (bit==0) */
    value &= ~(1<<9);
    #else
    @@ -764,7 +771,7 @@ asmlinkage void smp_error_interrupt(void
    apic_write(APIC_ESR, 0);
    v1 = apic_read(APIC_ESR);
    ack_APIC_irq();
    - irq_err_count++;
    + atomic_inc(&irq_err_count);

    /* Here is what the APIC error bits mean:
    0: Send CS error
    diff -up --recursive --new-file linux-2.4.1.macro/arch/i386/kernel/i8259.c linux-2.4.1/arch/i386/kernel/i8259.c
    --- linux-2.4.1.macro/arch/i386/kernel/i8259.c Mon Nov 20 18:01:58 2000
    +++ linux-2.4.1/arch/i386/kernel/i8259.c Sun Feb 11 19:54:33 2001
    @@ -12,6 +12,7 @@
    #include <linux/init.h>
    #include <linux/kernel_stat.h>

    +#include <asm/atomic.h>
    #include <asm/system.h>
    #include <asm/io.h>
    #include <asm/irq.h>
    @@ -321,7 +322,7 @@ spurious_8259A_irq:
    printk("spurious 8259A interrupt: IRQ%d.\n", irq);
    spurious_irq_mask |= irqmask;
    }
    - irq_err_count++;
    + atomic_inc(&irq_err_count);
    /*
    * Theoretically we do not have to handle this IRQ,
    * but in Linux this does not cause problems and is
    diff -up --recursive --new-file linux-2.4.1.macro/arch/i386/kernel/io_apic.c linux-2.4.1/arch/i386/kernel/io_apic.c
    --- linux-2.4.1.macro/arch/i386/kernel/io_apic.c Sat Feb 3 12:05:49 2001
    +++ linux-2.4.1/arch/i386/kernel/io_apic.c Tue Feb 13 19:59:55 2001
    @@ -33,6 +33,8 @@
    #include <asm/smp.h>
    #include <asm/desc.h>

    +#define APIC_LOCKUP_DEBUG
    +
    static spinlock_t ioapic_lock = SPIN_LOCK_UNLOCKED;

    /*
    @@ -122,8 +124,14 @@ static void add_pin_to_irq(unsigned int
    static void name##_IO_APIC_irq (unsigned int irq) \
    __DO_ACTION(R, ACTION, FINAL)

    -DO_ACTION( __mask, 0, |= 0x00010000, io_apic_sync(entry->apic))/* mask = 1 */
    -DO_ACTION( __unmask, 0, &= 0xfffeffff, ) /* mask = 0 */
    +DO_ACTION( __mask, 0, |= 0x00010000, io_apic_sync(entry->apic) )
    + /* mask = 1 */
    +DO_ACTION( __unmask, 0, &= 0xfffeffff, )
    + /* mask = 0 */
    +DO_ACTION( __mask_and_edge, 0, = (reg & 0xffff7fff) | 0x00010000, )
    + /* mask = 1, trigger = 0 */
    +DO_ACTION( __unmask_and_level, 0, = (reg & 0xfffeffff) | 0x00008000, )
    + /* mask = 0, trigger = 1 */

    static void mask_IO_APIC_irq (unsigned int irq)
    {
    @@ -847,6 +855,8 @@ void /*__init*/ print_local_APIC(void *

    v = apic_read(APIC_EOI);
    printk(KERN_DEBUG "... APIC EOI: %08x\n", v);
    + v = apic_read(APIC_RRR);
    + printk(KERN_DEBUG "... APIC RRR: %08x\n", v);
    v = apic_read(APIC_LDR);
    printk(KERN_DEBUG "... APIC LDR: %08x\n", v);
    v = apic_read(APIC_DFR);
    @@ -1191,12 +1201,61 @@ static unsigned int startup_level_ioapic
    #define enable_level_ioapic_irq unmask_IO_APIC_irq
    #define disable_level_ioapic_irq mask_IO_APIC_irq

    -static void end_level_ioapic_irq (unsigned int i)
    +static void end_level_ioapic_irq (unsigned int irq)
    {
    + unsigned long v;
    +
    +/*
    + * It appears there is an erratum which affects at least version 0x11
    + * of I/O APIC (that's the 82093AA and cores integrated into various
    + * chipsets). Under certain conditions a level-triggered interrupt is
    + * erroneously delivered as edge-triggered one but the respective IRR
    + * bit gets set nevertheless. As a result the I/O unit expects an EOI
    + * message but it will never arrive and further interrupts are blocked
    + * from the source. The exact reason is so far unknown, but the
    + * phenomenon was observed when two consecutive interrupt requests
    + * from a given source get delivered to the same CPU and the source is
    + * temporarily disabled in between.
    + *
    + * A workaround is to simulate an EOI message manually. We achieve it
    + * by setting the trigger mode to edge and then to level when the edge
    + * trigger mode gets detected in the TMR of a local APIC for a
    + * level-triggered interrupt. We mask the source for the time of the
    + * operation to prevent an edge-triggered interrupt escaping meanwhile.
    + * The idea is from Manfred Spraul. --macro
    + */
    + v = apic_read(APIC_TMR + ((IO_APIC_VECTOR(irq) & ~0x1f) >> 1));
    +
    ack_APIC_irq();
    +
    + if (!(v & (1 << (IO_APIC_VECTOR(irq) & 0x1f)))) {
    +#ifdef APIC_MISMATCH_DEBUG
    + atomic_inc(&irq_mis_count);
    +#endif
    + spin_lock(&ioapic_lock);
    + __mask_and_edge_IO_APIC_irq(irq);
    +#ifdef APIC_LOCKUP_DEBUG
    + for (;;) {
    + struct irq_pin_list *entry = irq_2_pin + irq;
    + unsigned int reg;
    +
    + if (entry->pin == -1)
    + break;
    + reg = io_apic_read(entry->apic, 0x10 + entry->pin * 2);
    + if (reg & 0x00004000)
    + printk(KERN_CRIT "Aieee!!! Remote IRR"
    + " still set after unlock!\n");
    + if (!entry->next)
    + break;
    + entry = irq_2_pin + entry->next;
    + }
    +#endif
    + __unmask_and_level_IO_APIC_irq(irq);
    + spin_unlock(&ioapic_lock);
    + }
    }

    -static void mask_and_ack_level_ioapic_irq (unsigned int i) { /* nothing */ }
    +static void mask_and_ack_level_ioapic_irq (unsigned int irq) { /* nothing */ }

    static void set_ioapic_affinity (unsigned int irq, unsigned long mask)
    {
    diff -up --recursive --new-file linux-2.4.1.macro/arch/i386/kernel/irq.c linux-2.4.1/arch/i386/kernel/irq.c
    --- linux-2.4.1.macro/arch/i386/kernel/irq.c Wed Dec 13 23:54:27 2000
    +++ linux-2.4.1/arch/i386/kernel/irq.c Mon Feb 12 13:37:37 2001
    @@ -33,6 +33,7 @@
    #include <linux/irq.h>
    #include <linux/proc_fs.h>

    +#include <asm/atomic.h>
    #include <asm/io.h>
    #include <asm/smp.h>
    #include <asm/system.h>
    @@ -119,7 +120,12 @@ struct hw_interrupt_type no_irq_type = {
    end_none
    };

    -volatile unsigned long irq_err_count;
    +atomic_t irq_err_count;
    +#ifdef CONFIG_X86_IO_APIC
    +#ifdef APIC_MISMATCH_DEBUG
    +atomic_t irq_mis_count;
    +#endif
    +#endif

    /*
    * Generic, controller-independent functions:
    @@ -167,7 +173,12 @@ int get_irq_list(char *buf)
    apic_timer_irqs[cpu_logical_map(j)]);
    p += sprintf(p, "\n");
    #endif
    - p += sprintf(p, "ERR: %10lu\n", irq_err_count);
    + p += sprintf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
    +#ifdef CONFIG_X86_IO_APIC
    +#ifdef APIC_MISMATCH_DEBUG
    + p += sprintf(p, "MIS: %10u\n", atomic_read(&irq_mis_count));
    +#endif
    +#endif
    return p - buf;
    }

    diff -up --recursive --new-file linux-2.4.1.macro/include/asm-i386/hw_irq.h linux-2.4.1/include/asm-i386/hw_irq.h
    --- linux-2.4.1.macro/include/asm-i386/hw_irq.h Sat Feb 3 13:12:29 2001
    +++ linux-2.4.1/include/asm-i386/hw_irq.h Sun Feb 11 20:02:57 2001
    @@ -13,6 +13,7 @@
    */

    #include <linux/config.h>
    +#include <asm/atomic.h>
    #include <asm/irq.h>

    /*
    @@ -83,7 +84,9 @@ extern int IO_APIC_get_PCI_irq_vector(in
    extern void send_IPI(int dest, int vector);

    extern unsigned long io_apic_irqs;
    -extern volatile unsigned long irq_err_count;
    +
    +extern atomic_t irq_err_count;
    +extern atomic_t irq_mis_count;

    extern char _stext, _etext;

    diff -up --recursive --new-file linux-2.4.1.macro/include/asm-i386/io_apic.h linux-2.4.1/include/asm-i386/io_apic.h
    --- linux-2.4.1.macro/include/asm-i386/io_apic.h Wed Nov 22 21:34:56 2000
    +++ linux-2.4.1/include/asm-i386/io_apic.h Mon Feb 12 13:41:02 2001
    @@ -12,6 +12,8 @@

    #ifdef CONFIG_X86_IO_APIC

    +#define APIC_MISMATCH_DEBUG
    +
    #define IO_APIC_BASE(idx) \
    ((volatile int *)__fix_to_virt(FIX_IO_APIC_BASE_0 + idx))

    diff -up --recursive --new-file linux-2.4.1.macro/include/linux/irq.h linux-2.4.1/include/linux/irq.h
    --- linux-2.4.1.macro/include/linux/irq.h Sat Feb 3 13:12:29 2001
    +++ linux-2.4.1/include/linux/irq.h Sun Feb 11 20:08:41 2001
    @@ -62,7 +62,4 @@ extern int setup_irq(unsigned int , stru
    extern hw_irq_controller no_irq_type; /* needed in every arch ? */
    extern void no_action(int cpl, void *dev_id, struct pt_regs *regs);

    -extern volatile unsigned long irq_err_count;
    -
    #endif /* __asm_h */
    -
    -
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