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* The asyncd kernel daemon. This handles paging on behalf of
* processes that receive page faults due to remote (async) memory
* accesses.
*
* Idea and skeleton code courtesy of David Miller (bless his cotton socks)
*
* Implemented by tridge
*/
#include <linux/mm.h>
#include <linux/malloc.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/swap.h>
#include <linux/fs.h>
#include <linux/config.h>
#include <linux/interrupt.h>
#include <asm/dma.h>
#include <asm/system.h> /* for cli()/sti() */
#include <asm/segment.h> /* for memcpy_to/fromfs */
#include <asm/bitops.h>
#include <asm/pgtable.h>
#define DEBUG 0
#define WRITE_LIMIT 100
#define LOOP_LIMIT 200
static struct {
int faults, read, write, success, failure, errors;
} stats;
/*
* The wait queue for waking up the async daemon:
*/
static DECLARE_WAIT_QUEUE_HEAD(asyncd_wait);
struct async_job {
volatile struct async_job *next;
int taskid;
struct mm_struct *mm;
unsigned long address;
int write;
void (*callback)(int,unsigned long,int,int);
};
static volatile struct async_job *async_queue = NULL;
static volatile struct async_job *async_queue_end = NULL;
static void add_to_async_queue(int taskid,
struct mm_struct *mm,
unsigned long address,
int write,
void (*callback)(int,unsigned long,int,int))
{
struct async_job *a = kmalloc(sizeof(*a),GFP_ATOMIC);
if (!a) {
printk("ERROR: out of memory in asyncd\n");
a->callback(taskid,address,write,1);
return;
}
if (write)
stats.write++;
else
stats.read++;
a->next = NULL;
a->taskid = taskid;
a->mm = mm;
a->address = address;
a->write = write;
a->callback = callback;
if (!async_queue) {
async_queue = a;
} else {
async_queue_end->next = a;
}
async_queue_end = a;
}
void async_fault(unsigned long address, int write, int taskid,
void (*callback)(int,unsigned long,int,int))
{
#warning Need some fixing here... -DaveM
struct task_struct *tsk = current /* XXX task[taskid] */;
struct mm_struct *mm = tsk->mm;
stats.faults++;
#if 0
printk("paging in %x for task=%d\n",address,taskid);
#endif
add_to_async_queue(taskid, mm, address, write, callback);
wake_up(&asyncd_wait);
mark_bh(TQUEUE_BH);
}
static int fault_in_page(int taskid,
struct vm_area_struct *vma,
unsigned long address, int write)
{
static unsigned last_address;
static int last_task, loop_counter;
#warning Need some fixing here... -DaveM
struct task_struct *tsk = current /* XXX task[taskid] */;
pgd_t *pgd;
pmd_t *pmd;
pte_t *pte;
if (!tsk || !tsk->mm)
return 1;
if (!vma || (write && !(vma->vm_flags & VM_WRITE)))
goto bad_area;
if (vma->vm_start > address)
goto bad_area;
if (address == last_address && taskid == last_task) {
loop_counter++;
} else {
loop_counter = 0;
last_address = address;
last_task = taskid;
}
if (loop_counter == WRITE_LIMIT && !write) {
printk("MSC bug? setting write request\n");
stats.errors++;
write = 1;
}
if (loop_counter == LOOP_LIMIT) {
printk("MSC bug? failing request\n");
stats.errors++;
return 1;
}
pgd = pgd_offset(vma->vm_mm, address);
pmd = pmd_alloc(pgd,address);
if(!pmd)
goto no_memory;
pte = pte_alloc(pmd, address);
if(!pte)
goto no_memory;
if(!pte_present(*pte)) {
handle_mm_fault(tsk, vma, address, write);
goto finish_up;
}
set_pte(pte, pte_mkyoung(*pte));
flush_tlb_page(vma, address);
if(!write)
goto finish_up;
if(pte_write(*pte)) {
set_pte(pte, pte_mkdirty(*pte));
flush_tlb_page(vma, address);
goto finish_up;
}
handle_mm_fault(tsk, vma, address, write);
/* Fall through for do_wp_page */
finish_up:
stats.success++;
return 0;
no_memory:
stats.failure++;
oom(tsk);
return 1;
bad_area:
stats.failure++;
tsk->thread.sig_address = address;
tsk->thread.sig_desc = SUBSIG_NOMAPPING;
send_sig(SIGSEGV, tsk, 1);
return 1;
}
/* Note the semaphore operations must be done here, and _not_
* in async_fault().
*/
static void run_async_queue(void)
{
int ret;
unsigned flags;
while (async_queue) {
volatile struct async_job *a;
struct mm_struct *mm;
struct vm_area_struct *vma;
save_flags(flags); cli();
a = async_queue;
async_queue = async_queue->next;
restore_flags(flags);
mm = a->mm;
down(&mm->mmap_sem);
vma = find_vma(mm, a->address);
ret = fault_in_page(a->taskid,vma,a->address,a->write);
#if DEBUG
printk("fault_in_page(task=%d addr=%x write=%d) = %d\n",
a->taskid,a->address,a->write,ret);
#endif
a->callback(a->taskid,a->address,a->write,ret);
up(&mm->mmap_sem);
kfree_s((void *)a,sizeof(*a));
}
}
#if CONFIG_AP1000
static void asyncd_info(void)
{
printk("CID(%d) faults: total=%d read=%d write=%d success=%d fail=%d err=%d\n",
mpp_cid(),stats.faults, stats.read, stats.write, stats.success,
stats.failure, stats.errors);
}
#endif
/*
* The background async daemon.
* Started as a kernel thread from the init process.
*/
int asyncd(void *unused)
{
current->session = 1;
current->pgrp = 1;
sprintf(current->comm, "asyncd");
sigfillset(¤t->blocked); /* block all signals */
recalc_sigpending(current);
/* Give asyncd a realtime priority. */
current->policy = SCHED_FIFO;
current->priority = 32; /* Fixme --- we need to standardise our
namings for POSIX.4 realtime scheduling
priorities. */
printk("Started asyncd\n");
#if CONFIG_AP1000
bif_add_debug_key('a',asyncd_info,"stats on asyncd");
#endif
while (1) {
unsigned flags;
save_flags(flags); cli();
while (!async_queue) {
spin_lock_irq(¤t->sigmask_lock);
flush_signals(current);
spin_unlock_irq(¤t->sigmask_lock);
interruptible_sleep_on(&asyncd_wait);
}
restore_flags(flags);
run_async_queue();
}
}
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