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 #ifdef RWSEM_IS_LOCKED_TAKES_WAIT_LOCK
  31 /*
  32  * A race condition in rwsem_is_locked() was fixed in Linux 2.6.33 and the fix
  33  * was backported to RHEL5 as of kernel 2.6.18-190.el5.  Details can be found
  34  * here:
  35  *
  36  * https://bugzilla.redhat.com/show_bug.cgi?id=526092
  37
  38  * The race condition was fixed in the kernel by acquiring the semaphore's
  39  * wait_lock inside rwsem_is_locked().  The SPL worked around the race
  40  * condition by acquiring the wait_lock before calling that function, but
  41  * with the fix in place we must not do that.
  42  */
  43
  44 #define spl_rwsem_is_locked(rwsem)                                      \
  45 ({                                                                      \
  46         rwsem_is_locked(rwsem);                                         \
  47 })
  48
  49 #else
  50
  51 #define spl_rwsem_is_locked(rwsem)                                      \
  52 ({                                                                      \
  53         unsigned long _flags_;                                          \
  54         int _rc_;                                                       \
  55         spin_lock_irqsave(&rwsem->wait_lock, _flags_);                  \
  56         _rc_ = rwsem_is_locked(rwsem);                                  \
  57         spin_unlock_irqrestore(&rwsem->wait_lock, _flags_);             \
  58         _rc_;                                                           \
  59 })
  60
  61 #endif /* RWSEM_IS_LOCKED_TAKES_WAIT_LOCK */
  62
  63 #endif /* _SPL_RWSEM_COMPAT_H */