/* * Copyright (c) 2000-2006 Silicon Graphics, Inc. * All Rights Reserved. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation. * * This program is distributed in the hope that it would be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ #ifndef __XFS_SUPPORT_MRLOCK_H__ #define __XFS_SUPPORT_MRLOCK_H__ #include <linux/rwsem.h> enum { MR_NONE, MR_ACCESS, MR_UPDATE }; typedef struct { struct rw_semaphore mr_lock; int mr_writer; } mrlock_t; #define mrinit(mrp, name) \ do { (mrp)->mr_writer = 0; init_rwsem(&(mrp)->mr_lock); } while (0) #define mrlock_init(mrp, t,n,s) mrinit(mrp, n) #define mrfree(mrp) do { } while (0) #define mraccess(mrp) mraccessf(mrp, 0) #define mrupdate(mrp) mrupdatef(mrp, 0) static inline void mraccessf(mrlock_t *mrp, int flags) { down_read(&mrp->mr_lock); } static inline void mrupdatef(mrlock_t *mrp, int flags) { down_write(&mrp->mr_lock); mrp->mr_writer = 1; } static inline int mrtryaccess(mrlock_t *mrp) { return down_read_trylock(&mrp->mr_lock); } static inline int mrtryupdate(mrlock_t *mrp) { if (!down_write_trylock(&mrp->mr_lock)) return 0; mrp->mr_writer = 1; return 1; } static inline void mrunlock(mrlock_t *mrp) { if (mrp->mr_writer) { mrp->mr_writer = 0; up_write(&mrp->mr_lock); } else { up_read(&mrp->mr_lock); } } static inline void mrdemote(mrlock_t *mrp) { mrp->mr_writer = 0; downgrade_write(&mrp->mr_lock); } #ifdef DEBUG /* * Debug-only routine, without some platform-specific asm code, we can * now only answer requests regarding whether we hold the lock for write * (reader state is outside our visibility, we only track writer state). * Note: means !ismrlocked would give false positives, so don't do that. */ static inline int ismrlocked(mrlock_t *mrp, int type) { if (mrp && type == MR_UPDATE) return mrp->mr_writer; return 1; } #endif #endif /* __XFS_SUPPORT_MRLOCK_H__ */