mrlock.h 2.2 KB

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  1. /*
  2. * Copyright (c) 2000-2006 Silicon Graphics, Inc.
  3. * All Rights Reserved.
  4. *
  5. * This program is free software; you can redistribute it and/or
  6. * modify it under the terms of the GNU General Public License as
  7. * published by the Free Software Foundation.
  8. *
  9. * This program is distributed in the hope that it would 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. * You should have received a copy of the GNU General Public License
  15. * along with this program; if not, write the Free Software Foundation,
  16. * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  17. */
  18. #ifndef __XFS_SUPPORT_MRLOCK_H__
  19. #define __XFS_SUPPORT_MRLOCK_H__
  20. #include <linux/rwsem.h>
  21. enum { MR_NONE, MR_ACCESS, MR_UPDATE };
  22. typedef struct {
  23. struct rw_semaphore mr_lock;
  24. int mr_writer;
  25. } mrlock_t;
  26. #define mrinit(mrp, name) \
  27. do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0)
  28. #define mrlock_init(mrp, t,n,s) mrinit(mrp, n)
  29. #define mrfree(mrp) do { } while (0)
  30. static inline void mraccess(mrlock_t *mrp)
  31. {
  32. down_read(&mrp->mr_lock);
  33. }
  34. static inline void mrupdate(mrlock_t *mrp)
  35. {
  36. down_write(&mrp->mr_lock);
  37. mrp->mr_writer = 1;
  38. }
  39. static inline int mrtryaccess(mrlock_t *mrp)
  40. {
  41. return down_read_trylock(&mrp->mr_lock);
  42. }
  43. static inline int mrtryupdate(mrlock_t *mrp)
  44. {
  45. if (!down_write_trylock(&mrp->mr_lock))
  46. return 0;
  47. mrp->mr_writer = 1;
  48. return 1;
  49. }
  50. static inline void mrunlock(mrlock_t *mrp)
  51. {
  52. if (mrp->mr_writer) {
  53. mrp->mr_writer = 0;
  54. up_write(&mrp->mr_lock);
  55. } else {
  56. up_read(&mrp->mr_lock);
  57. }
  58. }
  59. static inline void mrdemote(mrlock_t *mrp)
  60. {
  61. mrp->mr_writer = 0;
  62. downgrade_write(&mrp->mr_lock);
  63. }
  64. #ifdef DEBUG
  65. /*
  66. * Debug-only routine, without some platform-specific asm code, we can
  67. * now only answer requests regarding whether we hold the lock for write
  68. * (reader state is outside our visibility, we only track writer state).
  69. * Note: means !ismrlocked would give false positives, so don't do that.
  70. */
  71. static inline int ismrlocked(mrlock_t *mrp, int type)
  72. {
  73. if (mrp && type == MR_UPDATE)
  74. return mrp->mr_writer;
  75. return 1;
  76. }
  77. #endif
  78. #endif /* __XFS_SUPPORT_MRLOCK_H__ */