sched: make early bootup sched_clock() use safer

[wrt350n-kernel.git] / arch / x86 / kernel / smp_32.c

/*
 *      Intel SMP support routines.
 *
 *      (c) 1995 Alan Cox, Building #3 <alan@redhat.com>
 *      (c) 1998-99, 2000 Ingo Molnar <mingo@redhat.com>
 *
 *      This code is released under the GNU General Public License version 2 or
 *      later.
 */

#include <linux/init.h>

#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/kernel_stat.h>
#include <linux/mc146818rtc.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/module.h>

#include <asm/mtrr.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <mach_apic.h>

/*
 *      Some notes on x86 processor bugs affecting SMP operation:
 *
 *      Pentium, Pentium Pro, II, III (and all CPUs) have bugs.
 *      The Linux implications for SMP are handled as follows:
 *
 *      Pentium III / [Xeon]
 *              None of the E1AP-E3AP errata are visible to the user.
 *
 *      E1AP.   see PII A1AP
 *      E2AP.   see PII A2AP
 *      E3AP.   see PII A3AP
 *
 *      Pentium II / [Xeon]
 *              None of the A1AP-A3AP errata are visible to the user.
 *
 *      A1AP.   see PPro 1AP
 *      A2AP.   see PPro 2AP
 *      A3AP.   see PPro 7AP
 *
 *      Pentium Pro
 *              None of 1AP-9AP errata are visible to the normal user,
 *      except occasional delivery of 'spurious interrupt' as trap #15.
 *      This is very rare and a non-problem.
 *
 *      1AP.    Linux maps APIC as non-cacheable
 *      2AP.    worked around in hardware
 *      3AP.    fixed in C0 and above steppings microcode update.
 *              Linux does not use excessive STARTUP_IPIs.
 *      4AP.    worked around in hardware
 *      5AP.    symmetric IO mode (normal Linux operation) not affected.
 *              'noapic' mode has vector 0xf filled out properly.
 *      6AP.    'noapic' mode might be affected - fixed in later steppings
 *      7AP.    We do not assume writes to the LVT deassering IRQs
 *      8AP.    We do not enable low power mode (deep sleep) during MP bootup
 *      9AP.    We do not use mixed mode
 *
 *      Pentium
 *              There is a marginal case where REP MOVS on 100MHz SMP
 *      machines with B stepping processors can fail. XXX should provide
 *      an L1cache=Writethrough or L1cache=off option.
 *
 *              B stepping CPUs may hang. There are hardware work arounds
 *      for this. We warn about it in case your board doesn't have the work
 *      arounds. Basically that's so I can tell anyone with a B stepping
 *      CPU and SMP problems "tough".
 *
 *      Specific items [From Pentium Processor Specification Update]
 *
 *      1AP.    Linux doesn't use remote read
 *      2AP.    Linux doesn't trust APIC errors
 *      3AP.    We work around this
 *      4AP.    Linux never generated 3 interrupts of the same priority
 *              to cause a lost local interrupt.
 *      5AP.    Remote read is never used
 *      6AP.    not affected - worked around in hardware
 *      7AP.    not affected - worked around in hardware
 *      8AP.    worked around in hardware - we get explicit CS errors if not
 *      9AP.    only 'noapic' mode affected. Might generate spurious
 *              interrupts, we log only the first one and count the
 *              rest silently.
 *      10AP.   not affected - worked around in hardware
 *      11AP.   Linux reads the APIC between writes to avoid this, as per
 *              the documentation. Make sure you preserve this as it affects
 *              the C stepping chips too.
 *      12AP.   not affected - worked around in hardware
 *      13AP.   not affected - worked around in hardware
 *      14AP.   we always deassert INIT during bootup
 *      15AP.   not affected - worked around in hardware
 *      16AP.   not affected - worked around in hardware
 *      17AP.   not affected - worked around in hardware
 *      18AP.   not affected - worked around in hardware
 *      19AP.   not affected - worked around in BIOS
 *
 *      If this sounds worrying believe me these bugs are either ___RARE___,
 *      or are signal timing bugs worked around in hardware and there's
 *      about nothing of note with C stepping upwards.
 */

DEFINE_PER_CPU(struct tlb_state, cpu_tlbstate) ____cacheline_aligned = { &init_mm, 0, };

/*
 * the following functions deal with sending IPIs between CPUs.
 *
 * We use 'broadcast', CPU->CPU IPIs and self-IPIs too.
 */

static inline int __prepare_ICR (unsigned int shortcut, int vector)
{
        unsigned int icr = shortcut | APIC_DEST_LOGICAL;

        switch (vector) {
        default:
                icr |= APIC_DM_FIXED | vector;
                break;
        case NMI_VECTOR:
                icr |= APIC_DM_NMI;
                break;
        }
        return icr;
}

static inline int __prepare_ICR2 (unsigned int mask)
{
        return SET_APIC_DEST_FIELD(mask);
}

void __send_IPI_shortcut(unsigned int shortcut, int vector)
{
        /*
         * Subtle. In the case of the 'never do double writes' workaround
         * we have to lock out interrupts to be safe.  As we don't care
         * of the value read we use an atomic rmw access to avoid costly
         * cli/sti.  Otherwise we use an even cheaper single atomic write
         * to the APIC.
         */
        unsigned int cfg;

        /*
         * Wait for idle.
         */
        apic_wait_icr_idle();

        /*
         * No need to touch the target chip field
         */
        cfg = __prepare_ICR(shortcut, vector);

        /*
         * Send the IPI. The write to APIC_ICR fires this off.
         */
        apic_write_around(APIC_ICR, cfg);
}

void send_IPI_self(int vector)
{
        __send_IPI_shortcut(APIC_DEST_SELF, vector);
}

/*
 * This is used to send an IPI with no shorthand notation (the destination is
 * specified in bits 56 to 63 of the ICR).
 */
static inline void __send_IPI_dest_field(unsigned long mask, int vector)
{
        unsigned long cfg;

        /*
         * Wait for idle.
         */
        if (unlikely(vector == NMI_VECTOR))
                safe_apic_wait_icr_idle();
        else
                apic_wait_icr_idle();
                
        /*
         * prepare target chip field
         */
        cfg = __prepare_ICR2(mask);
        apic_write_around(APIC_ICR2, cfg);
                
        /*
         * program the ICR 
         */
        cfg = __prepare_ICR(0, vector);
                        
        /*
         * Send the IPI. The write to APIC_ICR fires this off.
         */
        apic_write_around(APIC_ICR, cfg);
}

/*
 * This is only used on smaller machines.
 */
void send_IPI_mask_bitmask(cpumask_t cpumask, int vector)
{
        unsigned long mask = cpus_addr(cpumask)[0];
        unsigned long flags;

        local_irq_save(flags);
        WARN_ON(mask & ~cpus_addr(cpu_online_map)[0]);
        __send_IPI_dest_field(mask, vector);
        local_irq_restore(flags);
}

void send_IPI_mask_sequence(cpumask_t mask, int vector)
{
        unsigned long flags;
        unsigned int query_cpu;

        /*
         * Hack. The clustered APIC addressing mode doesn't allow us to send 
         * to an arbitrary mask, so I do a unicasts to each CPU instead. This 
         * should be modified to do 1 message per cluster ID - mbligh
         */ 

        local_irq_save(flags);
        for_each_possible_cpu(query_cpu) {
                if (cpu_isset(query_cpu, mask)) {
                        __send_IPI_dest_field(cpu_to_logical_apicid(query_cpu),
                                              vector);
                }
        }
        local_irq_restore(flags);
}

#include <mach_ipi.h> /* must come after the send_IPI functions above for inlining */

/*
 *      Smarter SMP flushing macros. 
 *              c/o Linus Torvalds.
 *
 *      These mean you can really definitely utterly forget about
 *      writing to user space from interrupts. (Its not allowed anyway).
 *
 *      Optimizations Manfred Spraul <manfred@colorfullife.com>
 */

static cpumask_t flush_cpumask;
static struct mm_struct * flush_mm;
static unsigned long flush_va;
static DEFINE_SPINLOCK(tlbstate_lock);

/*
 * We cannot call mmdrop() because we are in interrupt context,
 * instead update mm->cpu_vm_mask.
 *
 * We need to reload %cr3 since the page tables may be going
 * away from under us..
 */
void leave_mm(int cpu)
{
        if (per_cpu(cpu_tlbstate, cpu).state == TLBSTATE_OK)
                BUG();
        cpu_clear(cpu, per_cpu(cpu_tlbstate, cpu).active_mm->cpu_vm_mask);
        load_cr3(swapper_pg_dir);
}
EXPORT_SYMBOL_GPL(leave_mm);

/*
 *
 * The flush IPI assumes that a thread switch happens in this order:
 * [cpu0: the cpu that switches]
 * 1) switch_mm() either 1a) or 1b)
 * 1a) thread switch to a different mm
 * 1a1) cpu_clear(cpu, old_mm->cpu_vm_mask);
 *      Stop ipi delivery for the old mm. This is not synchronized with
 *      the other cpus, but smp_invalidate_interrupt ignore flush ipis
 *      for the wrong mm, and in the worst case we perform a superfluous
 *      tlb flush.
 * 1a2) set cpu_tlbstate to TLBSTATE_OK
 *      Now the smp_invalidate_interrupt won't call leave_mm if cpu0
 *      was in lazy tlb mode.
 * 1a3) update cpu_tlbstate[].active_mm
 *      Now cpu0 accepts tlb flushes for the new mm.
 * 1a4) cpu_set(cpu, new_mm->cpu_vm_mask);
 *      Now the other cpus will send tlb flush ipis.
 * 1a4) change cr3.
 * 1b) thread switch without mm change
 *      cpu_tlbstate[].active_mm is correct, cpu0 already handles
 *      flush ipis.
 * 1b1) set cpu_tlbstate to TLBSTATE_OK
 * 1b2) test_and_set the cpu bit in cpu_vm_mask.
 *      Atomically set the bit [other cpus will start sending flush ipis],
 *      and test the bit.
 * 1b3) if the bit was 0: leave_mm was called, flush the tlb.
 * 2) switch %%esp, ie current
 *
 * The interrupt must handle 2 special cases:
 * - cr3 is changed before %%esp, ie. it cannot use current->{active_,}mm.
 * - the cpu performs speculative tlb reads, i.e. even if the cpu only
 *   runs in kernel space, the cpu could load tlb entries for user space
 *   pages.
 *
 * The good news is that cpu_tlbstate is local to each cpu, no
 * write/read ordering problems.
 */

/*
 * TLB flush IPI:
 *
 * 1) Flush the tlb entries if the cpu uses the mm that's being flushed.
 * 2) Leave the mm if we are in the lazy tlb mode.
 */

void smp_invalidate_interrupt(struct pt_regs *regs)
{
        unsigned long cpu;

        cpu = get_cpu();

        if (!cpu_isset(cpu, flush_cpumask))
                goto out;
                /* 
                 * This was a BUG() but until someone can quote me the
                 * line from the intel manual that guarantees an IPI to
                 * multiple CPUs is retried _only_ on the erroring CPUs
                 * its staying as a return
                 *
                 * BUG();
                 */
                 
        if (flush_mm == per_cpu(cpu_tlbstate, cpu).active_mm) {
                if (per_cpu(cpu_tlbstate, cpu).state == TLBSTATE_OK) {
                        if (flush_va == TLB_FLUSH_ALL)
                                local_flush_tlb();
                        else
                                __flush_tlb_one(flush_va);
                } else
                        leave_mm(cpu);
        }
        ack_APIC_irq();
        smp_mb__before_clear_bit();
        cpu_clear(cpu, flush_cpumask);
        smp_mb__after_clear_bit();
out:
        put_cpu_no_resched();
        __get_cpu_var(irq_stat).irq_tlb_count++;
}

void native_flush_tlb_others(const cpumask_t *cpumaskp, struct mm_struct *mm,
                             unsigned long va)
{
        cpumask_t cpumask = *cpumaskp;

        /*
         * A couple of (to be removed) sanity checks:
         *
         * - current CPU must not be in mask
         * - mask must exist :)
         */
        BUG_ON(cpus_empty(cpumask));
        BUG_ON(cpu_isset(smp_processor_id(), cpumask));
        BUG_ON(!mm);

#ifdef CONFIG_HOTPLUG_CPU
        /* If a CPU which we ran on has gone down, OK. */
        cpus_and(cpumask, cpumask, cpu_online_map);
        if (unlikely(cpus_empty(cpumask)))
                return;
#endif

        /*
         * i'm not happy about this global shared spinlock in the
         * MM hot path, but we'll see how contended it is.
         * AK: x86-64 has a faster method that could be ported.
         */
        spin_lock(&tlbstate_lock);
        
        flush_mm = mm;
        flush_va = va;
        cpus_or(flush_cpumask, cpumask, flush_cpumask);
        /*
         * We have to send the IPI only to
         * CPUs affected.
         */
        send_IPI_mask(cpumask, INVALIDATE_TLB_VECTOR);

        while (!cpus_empty(flush_cpumask))
                /* nothing. lockup detection does not belong here */
                cpu_relax();

        flush_mm = NULL;
        flush_va = 0;
        spin_unlock(&tlbstate_lock);
}
        
void flush_tlb_current_task(void)
{
        struct mm_struct *mm = current->mm;
        cpumask_t cpu_mask;

        preempt_disable();
        cpu_mask = mm->cpu_vm_mask;
        cpu_clear(smp_processor_id(), cpu_mask);

        local_flush_tlb();
        if (!cpus_empty(cpu_mask))
                flush_tlb_others(cpu_mask, mm, TLB_FLUSH_ALL);
        preempt_enable();
}

void flush_tlb_mm (struct mm_struct * mm)
{
        cpumask_t cpu_mask;

        preempt_disable();
        cpu_mask = mm->cpu_vm_mask;
        cpu_clear(smp_processor_id(), cpu_mask);

        if (current->active_mm == mm) {
                if (current->mm)
                        local_flush_tlb();
                else
                        leave_mm(smp_processor_id());
        }
        if (!cpus_empty(cpu_mask))
                flush_tlb_others(cpu_mask, mm, TLB_FLUSH_ALL);

        preempt_enable();
}

void flush_tlb_page(struct vm_area_struct * vma, unsigned long va)
{
        struct mm_struct *mm = vma->vm_mm;
        cpumask_t cpu_mask;

        preempt_disable();
        cpu_mask = mm->cpu_vm_mask;
        cpu_clear(smp_processor_id(), cpu_mask);

        if (current->active_mm == mm) {
                if(current->mm)
                        __flush_tlb_one(va);
                 else
                        leave_mm(smp_processor_id());
        }

        if (!cpus_empty(cpu_mask))
                flush_tlb_others(cpu_mask, mm, va);

        preempt_enable();
}
EXPORT_SYMBOL(flush_tlb_page);

static void do_flush_tlb_all(void* info)
{
        unsigned long cpu = smp_processor_id();

        __flush_tlb_all();
        if (per_cpu(cpu_tlbstate, cpu).state == TLBSTATE_LAZY)
                leave_mm(cpu);
}

void flush_tlb_all(void)
{
        on_each_cpu(do_flush_tlb_all, NULL, 1, 1);
}

/*
 * this function sends a 'reschedule' IPI to another CPU.
 * it goes straight through and wastes no time serializing
 * anything. Worst case is that we lose a reschedule ...
 */
static void native_smp_send_reschedule(int cpu)
{
        WARN_ON(cpu_is_offline(cpu));
        send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR);
}

/*
 * Structure and data for smp_call_function(). This is designed to minimise
 * static memory requirements. It also looks cleaner.
 */
static DEFINE_SPINLOCK(call_lock);

struct call_data_struct {
        void (*func) (void *info);
        void *info;
        atomic_t started;
        atomic_t finished;
        int wait;
};

void lock_ipi_call_lock(void)
{
        spin_lock_irq(&call_lock);
}

void unlock_ipi_call_lock(void)
{
        spin_unlock_irq(&call_lock);
}

static struct call_data_struct *call_data;

static void __smp_call_function(void (*func) (void *info), void *info,
                                int nonatomic, int wait)
{
        struct call_data_struct data;
        int cpus = num_online_cpus() - 1;

        if (!cpus)
                return;

        data.func = func;
        data.info = info;
        atomic_set(&data.started, 0);
        data.wait = wait;
        if (wait)
                atomic_set(&data.finished, 0);

        call_data = &data;
        mb();
        
        /* Send a message to all other CPUs and wait for them to respond */
        send_IPI_allbutself(CALL_FUNCTION_VECTOR);

        /* Wait for response */
        while (atomic_read(&data.started) != cpus)
                cpu_relax();

        if (wait)
                while (atomic_read(&data.finished) != cpus)
                        cpu_relax();
}


/**
 * smp_call_function_mask(): Run a function on a set of other CPUs.
 * @mask: The set of cpus to run on.  Must not include the current cpu.
 * @func: The function to run. This must be fast and non-blocking.
 * @info: An arbitrary pointer to pass to the function.
 * @wait: If true, wait (atomically) until function has completed on other CPUs.
 *
  * Returns 0 on success, else a negative status code.
 *
 * If @wait is true, then returns once @func has returned; otherwise
 * it returns just before the target cpu calls @func.
 *
 * You must not call this function with disabled interrupts or from a
 * hardware interrupt handler or from a bottom half handler.
 */
static int
native_smp_call_function_mask(cpumask_t mask,
                              void (*func)(void *), void *info,
                              int wait)
{
        struct call_data_struct data;
        cpumask_t allbutself;
        int cpus;

        /* Can deadlock when called with interrupts disabled */
        WARN_ON(irqs_disabled());

        /* Holding any lock stops cpus from going down. */
        spin_lock(&call_lock);

        allbutself = cpu_online_map;
        cpu_clear(smp_processor_id(), allbutself);

        cpus_and(mask, mask, allbutself);
        cpus = cpus_weight(mask);

        if (!cpus) {
                spin_unlock(&call_lock);
                return 0;
        }

        data.func = func;
        data.info = info;
        atomic_set(&data.started, 0);
        data.wait = wait;
        if (wait)
                atomic_set(&data.finished, 0);

        call_data = &data;
        mb();

        /* Send a message to other CPUs */
        if (cpus_equal(mask, allbutself))
                send_IPI_allbutself(CALL_FUNCTION_VECTOR);
        else
                send_IPI_mask(mask, CALL_FUNCTION_VECTOR);

        /* Wait for response */
        while (atomic_read(&data.started) != cpus)
                cpu_relax();

        if (wait)
                while (atomic_read(&data.finished) != cpus)
                        cpu_relax();
        spin_unlock(&call_lock);

        return 0;
}

static void stop_this_cpu (void * dummy)
{
        local_irq_disable();
        /*
         * Remove this CPU:
         */
        cpu_clear(smp_processor_id(), cpu_online_map);
        disable_local_APIC();
        if (cpu_data(smp_processor_id()).hlt_works_ok)
                for(;;) halt();
        for (;;);
}

/*
 * this function calls the 'stop' function on all other CPUs in the system.
 */

static void native_smp_send_stop(void)
{
        /* Don't deadlock on the call lock in panic */
        int nolock = !spin_trylock(&call_lock);
        unsigned long flags;

        local_irq_save(flags);
        __smp_call_function(stop_this_cpu, NULL, 0, 0);
        if (!nolock)
                spin_unlock(&call_lock);
        disable_local_APIC();
        local_irq_restore(flags);
}

/*
 * Reschedule call back. Nothing to do,
 * all the work is done automatically when
 * we return from the interrupt.
 */
void smp_reschedule_interrupt(struct pt_regs *regs)
{
        ack_APIC_irq();
        __get_cpu_var(irq_stat).irq_resched_count++;
}

void smp_call_function_interrupt(struct pt_regs *regs)
{
        void (*func) (void *info) = call_data->func;
        void *info = call_data->info;
        int wait = call_data->wait;

        ack_APIC_irq();
        /*
         * Notify initiating CPU that I've grabbed the data and am
         * about to execute the function
         */
        mb();
        atomic_inc(&call_data->started);
        /*
         * At this point the info structure may be out of scope unless wait==1
         */
        irq_enter();
        (*func)(info);
        __get_cpu_var(irq_stat).irq_call_count++;
        irq_exit();

        if (wait) {
                mb();
                atomic_inc(&call_data->finished);
        }
}

static int convert_apicid_to_cpu(int apic_id)
{
        int i;

        for_each_possible_cpu(i) {
                if (per_cpu(x86_cpu_to_apicid, i) == apic_id)
                        return i;
        }
        return -1;
}

int safe_smp_processor_id(void)
{
        int apicid, cpuid;

        if (!boot_cpu_has(X86_FEATURE_APIC))
                return 0;

        apicid = hard_smp_processor_id();
        if (apicid == BAD_APICID)
                return 0;

        cpuid = convert_apicid_to_cpu(apicid);

        return cpuid >= 0 ? cpuid : 0;
}

struct smp_ops smp_ops = {
        .smp_prepare_boot_cpu = native_smp_prepare_boot_cpu,
        .smp_prepare_cpus = native_smp_prepare_cpus,
        .cpu_up = native_cpu_up,
        .smp_cpus_done = native_smp_cpus_done,

        .smp_send_stop = native_smp_send_stop,
        .smp_send_reschedule = native_smp_send_reschedule,
        .smp_call_function_mask = native_smp_call_function_mask,
};
EXPORT_SYMBOL_GPL(smp_ops);