include/asm-generic/qspinlock_types.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * Queued spinlock
   4  *
   5  * (C) Copyright 2013-2015 Hewlett-Packard Development Company, L.P.
   6  *
   7  * Authors: Waiman Long <waiman.long@hp.com>
   8  */
   9 #ifndef __ASM_GENERIC_QSPINLOCK_TYPES_H
  10 #define __ASM_GENERIC_QSPINLOCK_TYPES_H
  11
  12 #include <linux/types.h>
  13
  14 typedef struct qspinlock {
  15         union {
  16                 atomic_t val;
  17
  18                 /*
  19                  * By using the whole 2nd least significant byte for the
  20                  * pending bit, we can allow better optimization of the lock
  21                  * acquisition for the pending bit holder.
  22                  */
  23 #ifdef __LITTLE_ENDIAN
  24                 struct {
  25                         u8      locked;
  26                         u8      pending;
  27                 };
  28                 struct {
  29                         u16     locked_pending;
  30                         u16     tail;
  31                 };
  32 #else
  33                 struct {
  34                         u16     tail;
  35                         u16     locked_pending;
  36                 };
  37                 struct {
  38                         u8      reserved[2];
  39                         u8      pending;
  40                         u8      locked;
  41                 };
  42 #endif
  43         };
  44 } arch_spinlock_t;
  45
  46 /*
  47  * Initializier
  48  */
  49 #define __ARCH_SPIN_LOCK_UNLOCKED       { { .val = ATOMIC_INIT(0) } }
  50
  51 /*
  52  * Bitfields in the atomic value:
  53  *
  54  * When NR_CPUS < 16K
  55  *  0- 7: locked byte
  56  *     8: pending
  57  *  9-15: not used
  58  * 16-17: tail index
  59  * 18-31: tail cpu (+1)
  60  *
  61  * When NR_CPUS >= 16K
  62  *  0- 7: locked byte
  63  *     8: pending
  64  *  9-10: tail index
  65  * 11-31: tail cpu (+1)
  66  */
  67 #define _Q_SET_MASK(type)       (((1U << _Q_ ## type ## _BITS) - 1)\
  68                                       << _Q_ ## type ## _OFFSET)
  69 #define _Q_LOCKED_OFFSET        0
  70 #define _Q_LOCKED_BITS          8
  71 #define _Q_LOCKED_MASK          _Q_SET_MASK(LOCKED)
  72
  73 #define _Q_PENDING_OFFSET       (_Q_LOCKED_OFFSET + _Q_LOCKED_BITS)
  74 #if CONFIG_NR_CPUS < (1U << 14)
  75 #define _Q_PENDING_BITS         8
  76 #else
  77 #define _Q_PENDING_BITS         1
  78 #endif
  79 #define _Q_PENDING_MASK         _Q_SET_MASK(PENDING)
  80
  81 #define _Q_TAIL_IDX_OFFSET      (_Q_PENDING_OFFSET + _Q_PENDING_BITS)
  82 #define _Q_TAIL_IDX_BITS        2
  83 #define _Q_TAIL_IDX_MASK        _Q_SET_MASK(TAIL_IDX)
  84
  85 #define _Q_TAIL_CPU_OFFSET      (_Q_TAIL_IDX_OFFSET + _Q_TAIL_IDX_BITS)
  86 #define _Q_TAIL_CPU_BITS        (32 - _Q_TAIL_CPU_OFFSET)
  87 #define _Q_TAIL_CPU_MASK        _Q_SET_MASK(TAIL_CPU)
  88
  89 #define _Q_TAIL_OFFSET          _Q_TAIL_IDX_OFFSET
  90 #define _Q_TAIL_MASK            (_Q_TAIL_IDX_MASK | _Q_TAIL_CPU_MASK)
  91
  92 #define _Q_LOCKED_VAL           (1U << _Q_LOCKED_OFFSET)
  93 #define _Q_PENDING_VAL          (1U << _Q_PENDING_OFFSET)
  94
  95 #endif /* __ASM_GENERIC_QSPINLOCK_TYPES_H */