include/asm-generic/qspinlock_types.h

   1 /*
   2  * Queued spinlock
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
  15  *
  16  * Authors: Waiman Long <waiman.long@hp.com>
  17  */
  18 #ifndef __ASM_GENERIC_QSPINLOCK_TYPES_H
  19 #define __ASM_GENERIC_QSPINLOCK_TYPES_H
  20
  21 /*
  22  * Including atomic.h with PARAVIRT on will cause compilation errors because
  23  * of recursive header file incluson via paravirt_types.h. So don't include
  24  * it if PARAVIRT is on.
  25  */
  26 #ifndef CONFIG_PARAVIRT
  27 #include <linux/types.h>
  28 #include <linux/atomic.h>
  29 #endif
  30
  31 typedef struct qspinlock {
  32         union {
  33                 atomic_t val;
  34
  35                 /*
  36                  * By using the whole 2nd least significant byte for the
  37                  * pending bit, we can allow better optimization of the lock
  38                  * acquisition for the pending bit holder.
  39                  */
  40 #ifdef __LITTLE_ENDIAN
  41                 struct {
  42                         u8      locked;
  43                         u8      pending;
  44                 };
  45                 struct {
  46                         u16     locked_pending;
  47                         u16     tail;
  48                 };
  49 #else
  50                 struct {
  51                         u16     tail;
  52                         u16     locked_pending;
  53                 };
  54                 struct {
  55                         u8      reserved[2];
  56                         u8      pending;
  57                         u8      locked;
  58                 };
  59 #endif
  60         };
  61 } arch_spinlock_t;
  62
  63 /*
  64  * Initializier
  65  */
  66 #define __ARCH_SPIN_LOCK_UNLOCKED       { { .val = ATOMIC_INIT(0) } }
  67
  68 /*
  69  * Bitfields in the atomic value:
  70  *
  71  * When NR_CPUS < 16K
  72  *  0- 7: locked byte
  73  *     8: pending
  74  *  9-15: not used
  75  * 16-17: tail index
  76  * 18-31: tail cpu (+1)
  77  *
  78  * When NR_CPUS >= 16K
  79  *  0- 7: locked byte
  80  *     8: pending
  81  *  9-10: tail index
  82  * 11-31: tail cpu (+1)
  83  */
  84 #define _Q_SET_MASK(type)       (((1U << _Q_ ## type ## _BITS) - 1)\
  85                                       << _Q_ ## type ## _OFFSET)
  86 #define _Q_LOCKED_OFFSET        0
  87 #define _Q_LOCKED_BITS          8
  88 #define _Q_LOCKED_MASK          _Q_SET_MASK(LOCKED)
  89
  90 #define _Q_PENDING_OFFSET       (_Q_LOCKED_OFFSET + _Q_LOCKED_BITS)
  91 #if CONFIG_NR_CPUS < (1U << 14)
  92 #define _Q_PENDING_BITS         8
  93 #else
  94 #define _Q_PENDING_BITS         1
  95 #endif
  96 #define _Q_PENDING_MASK         _Q_SET_MASK(PENDING)
  97
  98 #define _Q_TAIL_IDX_OFFSET      (_Q_PENDING_OFFSET + _Q_PENDING_BITS)
  99 #define _Q_TAIL_IDX_BITS        2
 100 #define _Q_TAIL_IDX_MASK        _Q_SET_MASK(TAIL_IDX)
 101
 102 #define _Q_TAIL_CPU_OFFSET      (_Q_TAIL_IDX_OFFSET + _Q_TAIL_IDX_BITS)
 103 #define _Q_TAIL_CPU_BITS        (32 - _Q_TAIL_CPU_OFFSET)
 104 #define _Q_TAIL_CPU_MASK        _Q_SET_MASK(TAIL_CPU)
 105
 106 #define _Q_TAIL_OFFSET          _Q_TAIL_IDX_OFFSET
 107 #define _Q_TAIL_MASK            (_Q_TAIL_IDX_MASK | _Q_TAIL_CPU_MASK)
 108
 109 #define _Q_LOCKED_VAL           (1U << _Q_LOCKED_OFFSET)
 110 #define _Q_PENDING_VAL          (1U << _Q_PENDING_OFFSET)
 111
 112 #endif /* __ASM_GENERIC_QSPINLOCK_TYPES_H */