include/linux/rwsem_compat.h

   1 /*****************************************************************************\
   2  *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
   3  *  Copyright (C) 2007 The Regents of the University of California.
   4  *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
   5  *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
   6  *  UCRL-CODE-235197
   7  *
   8  *  This file is part of the SPL, Solaris Porting Layer.
   9  *  For details, see <http://github.com/behlendorf/spl/>.
  10  *
  11  *  The SPL is free software; you can redistribute it and/or modify it
  12  *  under the terms of the GNU General Public License as published by the
  13  *  Free Software Foundation; either version 2 of the License, or (at your
  14  *  option) any later version.
  15  *
  16  *  The SPL is distributed in the hope that it will be useful, but WITHOUT
  17  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  19  *  for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License along
  22  *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
  23 \*****************************************************************************/
  24
  25 #ifndef _SPL_RWSEM_COMPAT_H
  26 #define _SPL_RWSEM_COMPAT_H
  27
  28 #include <linux/rwsem.h>
  29
  30 #if defined(RWSEM_SPINLOCK_IS_RAW)
  31 #define spl_rwsem_lock_irqsave(lk, fl)       raw_spin_lock_irqsave(lk, fl)
  32 #define spl_rwsem_unlock_irqrestore(lk, fl)  raw_spin_unlock_irqrestore(lk, fl)
  33 #define spl_rwsem_trylock_irqsave(lk, fl)    raw_spin_trylock_irqsave(lk, fl)
  34 #else
  35 #define spl_rwsem_lock_irqsave(lk, fl)       spin_lock_irqsave(lk, fl)
  36 #define spl_rwsem_unlock_irqrestore(lk, fl)  spin_unlock_irqrestore(lk, fl)
  37 #define spl_rwsem_trylock_irqsave(lk, fl)    spin_trylock_irqsave(lk, fl)
  38 #endif /* RWSEM_SPINLOCK_IS_RAW */
  39
  40 /*
  41  * Prior to Linux 2.6.33 there existed a race condition in rwsem_is_locked().
  42  * The semaphore's activity was checked outside of the wait_lock which
  43  * could result in some readers getting the incorrect activity value.
  44  *
  45  * When a kernel without this fix is detected the SPL takes responsibility
  46  * for acquiring the wait_lock to avoid this race.
  47  */
  48 #if defined(RWSEM_IS_LOCKED_TAKES_WAIT_LOCK)
  49 #define spl_rwsem_is_locked(rwsem)           rwsem_is_locked(rwsem)
  50 #else
  51 static inline int
  52 spl_rwsem_is_locked(struct rw_semaphore *rwsem)
  53 {
  54         unsigned long flags;
  55         int rc = 1;
  56
  57         if (spl_rwsem_trylock_irqsave(&rwsem->wait_lock, flags)) {
  58                 rc = rwsem_is_locked(rwsem);
  59                 spl_rwsem_unlock_irqrestore(&rwsem->wait_lock, flags);
  60         }
  61
  62         return (rc);
  63 }
  64 #endif /* RWSEM_IS_LOCKED_TAKES_WAIT_LOCK */
  65
  66 #endif /* _SPL_RWSEM_COMPAT_H */