/* * This file is part of the SPL: Solaris Porting Layer. * * Copyright (c) 2009 Lawrence Livermore National Security, LLC. * Produced at Lawrence Livermore National Laboratory * Written by: * Brian Behlendorf , * Herb Wartens , * Jim Garlick * UCRL-CODE-235197 * * This 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. * * This 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 this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #ifndef _SPL_RWLOCK_H #define _SPL_RWLOCK_H #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; /* * For the generic and x86 implementations of rw-semaphores the following * is true. If your semaphore implementation internally represents the * semaphore state differently special case handling will be 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 */ #define SEM(rwp) ((struct rw_semaphore *)(rwp)) #if defined(CONFIG_RWSEM_GENERIC_SPINLOCK) # define RW_COUNT(rwp) (SEM(rwp)->activity) # define rw_exit_locked(rwp) __up_read_locked(rwp) # define rw_tryenter_locked(rwp) __down_write_trylock_locked(rwp) extern void __up_read_locked(struct rw_semaphore *); extern int __down_write_trylock_locked(struct rw_semaphore *); #else # define RW_COUNT(rwp) (SEM(rwp)->count & RWSEM_ACTIVE_MASK) # define rw_exit_locked(rwp) up_read(rwp) # define rw_tryenter_locked(rwp) down_write_trylock(rwp) #endif static inline kthread_t * spl_rw_get_owner(krwlock_t *rwp) { return rwp->rw_owner; } static inline void spl_rw_set_owner(krwlock_t *rwp) { unsigned long flags; spin_lock_irqsave(&SEM(rwp)->wait_lock, flags); rwp->rw_owner = current; spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); } static inline void spl_rw_clear_owner(krwlock_t *rwp) { unsigned long flags; spin_lock_irqsave(&SEM(rwp)->wait_lock, flags); rwp->rw_owner = NULL; spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); } static inline kthread_t * rw_owner(krwlock_t *rwp) { unsigned long flags; kthread_t *owner; spin_lock_irqsave(&SEM(rwp)->wait_lock, flags); owner = spl_rw_get_owner(rwp); spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); return owner; } static inline int RW_READ_HELD(krwlock_t *rwp) { unsigned long flags; int rc; spin_lock_irqsave(&SEM(rwp)->wait_lock, flags); rc = ((RW_COUNT(rwp) > 0) && (spl_rw_get_owner(rwp) == NULL)); spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); return rc; } static inline int RW_WRITE_HELD(krwlock_t *rwp) { unsigned long flags; int rc; spin_lock_irqsave(&SEM(rwp)->wait_lock, flags); rc = ((RW_COUNT(rwp) < 0) && (spl_rw_get_owner(rwp) == current)); spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); return rc; } static inline int RW_LOCK_HELD(krwlock_t *rwp) { unsigned long flags; int rc; spin_lock_irqsave(&SEM(rwp)->wait_lock, flags); rc = (RW_COUNT(rwp) != 0); spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags); return rc; } /* * 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) \ ({ \ init_rwsem(SEM(rwp)); \ 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: \ SBUG(); \ } \ _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: \ SBUG(); \ } \ }) #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)); \ }) #define rw_tryupgrade(rwp) \ ({ \ unsigned long _flags_; \ int _rc_ = 0; \ \ spin_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \ if (list_empty(&SEM(rwp)->wait_list) && (RW_COUNT(rwp) == 1)) { \ rw_exit_locked(SEM(rwp)); \ VERIFY(_rc_ = rw_tryenter_locked(SEM(rwp))); \ (rwp)->rw_owner = current; \ } \ spin_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \ _rc_; \ }) int spl_rw_init(void); void spl_rw_fini(void); #endif /* _SPL_RWLOCK_H */