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e7a99dab2b
The Linux kernel's rwsem's have never provided an interface to allow a reader to be upgraded to a writer. Historically, this functionality has been implemented by a SPL wrapper function. However, this approach depends on internal knowledge of the rw_semaphore and is therefore rather brittle. Since the ZFS code must always be able to fallback to rw_exit() and rw_enter() when an rw_tryupgrade() fails; this functionality isn't critical. Furthermore, the only potentially performance sensitive consumer is dmu_zfetch() and no decrease in performance was observed with this change applied. See the PR comments for additional testing details. Therefore, it is being retired to make the build more robust and to simplify the rwlock implementation. Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #9029
29 lines
1.2 KiB
C
29 lines
1.2 KiB
C
/*
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://zfsonlinux.org/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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*
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* Solaris Porting Layer (SPL) Reader/Writer Lock Implementation.
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*/
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int spl_rw_init(void) { return 0; }
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void spl_rw_fini(void) { }
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