/*****************************************************************************\ * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC. * Copyright (C) 2007 The Regents of the University of California. * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). * Written by Brian Behlendorf . * UCRL-CODE-235197 * * This file is part of the SPL, Solaris Porting Layer. * For details, see . * * The SPL 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; either version 2 of the License, or (at your * option) any later version. * * The SPL is distributed in the hope that it will 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 the SPL. If not, see . \*****************************************************************************/ #ifndef _SPL_RWLOCK_H #define _SPL_RWLOCK_H #include #include #include typedef enum { RW_DRIVER = 2, RW_DEFAULT = 4 } krw_type_t; typedef enum { RW_NONE = 0, RW_WRITER = 1, RW_READER = 2 } krw_t; typedef struct { struct rw_semaphore rw_rwlock; kthread_t *rw_owner; } krwlock_t; #define SEM(rwp) ((struct rw_semaphore *)(rwp)) static inline void spl_rw_set_owner(krwlock_t *rwp) { unsigned long flags; spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags); rwp->rw_owner = current; spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); } static inline void spl_rw_clear_owner(krwlock_t *rwp) { unsigned long flags; spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags); rwp->rw_owner = NULL; spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); } static inline kthread_t * rw_owner(krwlock_t *rwp) { unsigned long flags; kthread_t *owner; spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, flags); owner = rwp->rw_owner; spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); return owner; } static inline int RW_READ_HELD(krwlock_t *rwp) { return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == NULL); } static inline int RW_WRITE_HELD(krwlock_t *rwp) { return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == current); } static inline int RW_LOCK_HELD(krwlock_t *rwp) { return spl_rwsem_is_locked(SEM(rwp)); } /* * The following functions must be a #define and not static inline. * This ensures that the native linux semaphore functions (down/up) * will be correctly located in the users code which is important * for the built in kernel lock analysis tools */ #define rw_init(rwp, name, type, arg) \ ({ \ static struct lock_class_key __key; \ \ __init_rwsem(SEM(rwp), #rwp, &__key); \ spl_rw_clear_owner(rwp); \ }) #define rw_destroy(rwp) \ ({ \ VERIFY(!RW_LOCK_HELD(rwp)); \ }) #define rw_tryenter(rwp, rw) \ ({ \ int _rc_ = 0; \ \ switch (rw) { \ case RW_READER: \ _rc_ = down_read_trylock(SEM(rwp)); \ break; \ case RW_WRITER: \ if ((_rc_ = down_write_trylock(SEM(rwp)))) \ spl_rw_set_owner(rwp); \ break; \ default: \ VERIFY(0); \ } \ _rc_; \ }) #define rw_enter(rwp, rw) \ ({ \ switch (rw) { \ case RW_READER: \ down_read(SEM(rwp)); \ break; \ case RW_WRITER: \ down_write(SEM(rwp)); \ spl_rw_set_owner(rwp); \ break; \ default: \ VERIFY(0); \ } \ }) #define rw_exit(rwp) \ ({ \ if (RW_WRITE_HELD(rwp)) { \ spl_rw_clear_owner(rwp); \ up_write(SEM(rwp)); \ } else { \ ASSERT(RW_READ_HELD(rwp)); \ up_read(SEM(rwp)); \ } \ }) #define rw_downgrade(rwp) \ ({ \ spl_rw_clear_owner(rwp); \ downgrade_write(SEM(rwp)); \ }) #if defined(CONFIG_RWSEM_GENERIC_SPINLOCK) /* * For the generic implementations of rw-semaphores the following is * true. If your semaphore implementation internally represents the * semaphore state differently then special case handling is required. * - if activity/count is 0 then there are no active readers or writers * - if activity/count is +ve then that is the number of active readers * - if activity/count is -1 then there is one active writer */ extern void __up_read_locked(struct rw_semaphore *); extern int __down_write_trylock_locked(struct rw_semaphore *); #define rw_tryupgrade(rwp) \ ({ \ unsigned long _flags_; \ int _rc_ = 0; \ \ spl_rwsem_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \ if ((list_empty(&SEM(rwp)->wait_list)) && \ (SEM(rwp)->activity == 1)) { \ __up_read_locked(SEM(rwp)); \ VERIFY(_rc_ = __down_write_trylock_locked(SEM(rwp))); \ (rwp)->rw_owner = current; \ } \ spl_rwsem_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \ _rc_; \ }) #else /* * rw_tryupgrade() can be implemented correctly but for each supported * arch we will need a custom implementation. For the x86 implementation * it looks like a custom cmpxchg() to atomically check and promote the * rwsem would be safe. For now that's not worth the trouble so in this * case rw_tryupgrade() has just been disabled. */ #define rw_tryupgrade(rwp) ({ 0; }) #endif int spl_rw_init(void); void spl_rw_fini(void); #endif /* _SPL_RWLOCK_H */