root/include/asm-alpha/mmu_context.h

/* */

INCLUDED FROM

DEFINITIONS

1. get_mmu_context

   1 #ifndef __ALPHA_MMU_CONTEXT_H
   2 #define __ALPHA_MMU_CONTEXT_H
   3 
   4 /*
   5  * get a new mmu context..
   6  *
   7  * Copyright (C) 1996, Linus Torvalds
   8  */
   9 
  10 #include <asm/pgtable.h>
  11 
  12 /*
  13  * The maximum ASN's the processor supports. On the EV4 this doesn't
  14  * matter as the pal-code doesn't use the ASNs anyway, on the EV5
  15  * EV5 this is 127.
  16  */
  17 #define MAX_ASN 127
  18 
  19 #define ASN_VERSION_SHIFT 32
  20 #define ASN_VERSION_MASK ((~0UL) << ASN_VERSION_SHIFT)
  21 #define ASN_FIRST_VERSION (1UL << ASN_VERSION_SHIFT)
  22 
  23 /*
  24  * NOTE! The way this is set up, the high bits of the "asn_cache" (and
  25  * the "mm->context") are the ASN _version_ code. A version of 0 is
  26  * always considered invalid, so to invalidate another process you only
  27  * need to do "p->mm->context = 0".
  28  *
  29  * If we need more ASN's than the processor has, we invalidate the old
  30  * user TLB's (tbiap()) and start a new ASN version. That will automatically
  31  * force a new asn for any other processes the next time they want to
  32  * run.
  33  */
  34 extern inline void get_mmu_context(struct task_struct *p)
     /*  */
  35 {
  36         static unsigned long asn_cache = ASN_FIRST_VERSION;
  37         struct mm_struct * mm = p->mm;
  38         unsigned long asn = mm->context;
  39 
  40         /* Check if our ASN is of an older version and thus invalid */
  41         if ((asn_cache ^ asn) & ASN_VERSION_MASK) {
  42                 /* get a new asn of the current version */
  43                 asn = asn_cache++;
  44                 /* check if it's legal.. */
  45                 if ((asn & ~ASN_VERSION_MASK) > MAX_ASN) {
  46                         /* start a new version, invalidate all old asn's */
  47                         tbiap();
  48                         asn_cache = (asn_cache & ASN_VERSION_MASK) + ASN_FIRST_VERSION;
  49                         if (!asn_cache)
  50                                 asn_cache = ASN_FIRST_VERSION;
  51                         asn = asn_cache++;
  52                 }
  53                 mm->context = asn;                      /* full version + asn */
  54                 p->tss.asn = asn & ~ASN_VERSION_MASK;   /* just asn */
  55         }
  56 }
  57 
  58 #endif

/* */