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https://gitlab.isc.org/isc-projects/bind9
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493b6a9f33
hp implementation requires an object for each thread accessing a hazard pointer. previous implementation had a hardcoded HP_MAX_THREAD value of 128, which failed on machines with lots of CPU cores (named uses 3n threads). We make isc__hp_max_threads configurable at startup, with the value set to 4*named_g_cpus. It's also important for this value not to be too big as we do linear searches on a list.
140 lines
4.5 KiB
C
140 lines
4.5 KiB
C
/*
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* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* See the COPYRIGHT file distributed with this work for additional
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* information regarding copyright ownership.
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*/
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/*
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* Hazard Pointer implementation.
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*
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* This work is based on C++ code available from:
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* https://github.com/pramalhe/ConcurrencyFreaks/
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*
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* Copyright (c) 2014-2016, Pedro Ramalhete, Andreia Correia
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Concurrency Freaks nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER>
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <isc/atomic.h>
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#include <isc/string.h>
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#include <isc/mem.h>
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#include <isc/types.h>
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#include <isc/util.h>
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/*%
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* Hazard pointers are a mechanism for protecting objects in memory
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* from being deleted by other threads while in use. This allows
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* safe lock-free data structures.
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*
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* This is an adaptation of the ConcurrencyFreaks implementation in C.
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* More details available at https://github.com/pramalhe/ConcurrencyFreaks,
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* in the file HazardPointers.hpp.
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*/
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typedef void
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(isc_hp_deletefunc_t)(void *);
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void
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isc_hp_init(int max_threads);
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/*%<
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* Initialize hazard pointer constants - isc__hp_max_threads. If more threads
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* will try to access hp it will assert.
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*/
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isc_hp_t *
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isc_hp_new(isc_mem_t *mctx, size_t max_hps, isc_hp_deletefunc_t *deletefunc);
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/*%<
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* Create a new hazard pointer array of size 'max_hps' (or a reasonable
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* default value if 'max_hps' is 0). The function 'deletefunc' will be
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* used to delete objects protected by hazard pointers when it becomes
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* safe to retire them.
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*/
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void
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isc_hp_destroy(isc_hp_t *hp);
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/*%<
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* Destroy a hazard pointer array and clean up all objects protected
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* by hazard pointers.
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*/
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void
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isc_hp_clear(isc_hp_t *hp);
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/*%<
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* Clear all hazard pointers in the array for the current thread.
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*
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* Progress condition: wait-free bounded (by max_hps)
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*/
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void
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isc_hp_clear_one(isc_hp_t *hp, int ihp);
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/*%<
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* Clear a specified hazard pointer in the array for the current thread.
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*
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* Progress condition: wait-free population oblivious.
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*/
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uintptr_t
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isc_hp_protect(isc_hp_t *hp, int ihp, atomic_uintptr_t *atom);
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/*%<
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* Protect an object referenced by 'atom' with a hazard pointer for the
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* current thread.
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*
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* Progress condition: lock-free.
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*/
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uintptr_t
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isc_hp_protect_ptr(isc_hp_t *hp, int ihp, atomic_uintptr_t ptr);
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/*%<
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* This returns the same value that is passed as ptr, which is sometimes
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* useful.
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*
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* Progress condition: wait-free population oblivious.
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*/
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uintptr_t
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isc_hp_protect_release(isc_hp_t *hp, int ihp, atomic_uintptr_t ptr);
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/*%<
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* Same as isc_hp_protect_ptr(), but explicitly uses memory_order_release.
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*
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* Progress condition: wait-free population oblivious.
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*/
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void
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isc_hp_retire(isc_hp_t *hp, uintptr_t ptr);
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/*%<
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* Retire an object that is no longer in use by any thread, calling
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* the delete function that was specified in isc_hp_new().
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*
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* Progress condition: wait-free bounded (by the number of threads squared)
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*/
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