734 lines
21 KiB
C
734 lines
21 KiB
C
/*
|
||
* ptw32_OLL_lock.c
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*
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* Description:
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* This translation unit implements extended reader/writer queue-based locks.
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*
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* --------------------------------------------------------------------------
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*
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* Pthreads-win32 - POSIX Threads Library for Win32
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* Copyright(C) 1998 John E. Bossom
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* Copyright(C) 1999,2005 Pthreads-win32 contributors
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*
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* Contact Email: rpj@callisto.canberra.edu.au
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*
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* The current list of contributors is contained
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* in the file CONTRIBUTORS included with the source
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* code distribution. The list can also be seen at the
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* following World Wide Web location:
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* http://sources.redhat.com/pthreads-win32/contributors.html
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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||
* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library in the file COPYING.LIB;
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* if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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/*
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* About the OLL lock (Scalable Reader-Writer Lock):
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*
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* OLL locks are queue-based locks similar to the MCS queue lock, where the queue
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* nodes are local to the thread but where reader threads can enter the critical
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* section immediately without going through a central guard lock if there are
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* already readers holding the lock.
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*
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* Covered by United States Patent Application 20100241774 (Oracle)
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*/
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#include "pthread.h"
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#include "sched.h"
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#include "implement.h"
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/*
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* C-SNZI support
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*/
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typedef union ptw32_oll_counter_t_ ptw32_oll_counter_t;
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typedef struct ptw32_oll_snziRoot_t_ ptw32_oll_snziRoot_t;
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typedef struct ptw32_oll_snziNode_t_ ptw32_oll_snziNode_t;
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typedef union ptw32_oll_snziNodeOrRoot_t_ ptw32_oll_snziNodeOrRoot_t;
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typedef struct ptw32_oll_queryResult_t_ ptw32_oll_queryResult_t;
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typedef struct ptw32_oll_ticket_t_ ptw32_oll_ticket_t;
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typedef struct ptw32_oll_csnzi_t_ ptw32_oll_csnzi_t;
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enum
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{
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ptw32_archWidth = sizeof(size_t)*8,
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ptw32_oll_countWidth = ptw32_archWidth-2
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};
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#define PTW32_OLL_MAXREADERS (((size_t)2<<(ptw32_oll_countWidth-1))-1)
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union ptw32_oll_counter_t_
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{
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size_t word : ptw32_archWidth;
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struct
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{
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/*
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* This needs to be a single word
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*
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* ------------------------------------
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* | STATE | ROOT | COUNT (readers) |
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* ------------------------------------
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* 63 / 31 62 / 30 61 / 29 .. 0
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*/
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size_t count : ptw32_oll_countWidth;
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size_t root : 1; /* ROOT or NODE */
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size_t state : 1; /* OPEN or CLOSED (root only) */
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} internal;
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};
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struct ptw32_oll_snziRoot_t_
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{
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/*
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* "counter" must be at same offset in both
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* ptw32_oll_snziNode_t and ptw32_oll_snziRoot_t
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*/
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ptw32_oll_counter_t counter;
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};
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enum
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{
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ptw32_oll_snziRoot_open = 0,
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ptw32_oll_snziRoot_closed = 1
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};
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enum
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{
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ptw32_oll_snzi_root = 0,
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ptw32_oll_snzi_node = 1
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};
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/*
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* Some common SNZI root whole-word states that can be used to set or compare
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* root words with a single operation.
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*/
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ptw32_oll_snziRoot_t ptw32_oll_snziRoot_openAndZero = {.counter.internal.count = 0,
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.counter.internal.root = ptw32_oll_snzi_root,
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.counter.internal.state = ptw32_oll_snziRoot_open};
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ptw32_oll_snziRoot_t ptw32_oll_snziRoot_closedAndZero = {.counter.internal.count = 0,
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.counter.internal.root = ptw32_oll_snzi_root,
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.counter.internal.state = ptw32_oll_snziRoot_closed};
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struct ptw32_oll_queryResult_t_
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{
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BOOL nonZero;
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BOOL open;
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};
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union ptw32_oll_snziNodeOrRoot_t_
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{
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ptw32_oll_snziRoot_t* rootPtr;
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ptw32_oll_snziNode_t* nodePtr;
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};
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struct ptw32_oll_snziNode_t_
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{
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/* "counter" must be at same offset in both
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* ptw32_oll_snziNode_t and ptw32_oll_snziRoot_t
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*/
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ptw32_oll_counter_t counter;
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ptw32_oll_snziNodeOrRoot_t parentPtr;
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};
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struct ptw32_oll_ticket_t_
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{
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ptw32_oll_snziNodeOrRoot_t snziNodeOrRoot;
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};
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ptw32_oll_ticket_t ptw32_oll_ticket_null = {NULL};
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struct ptw32_oll_csnzi_t_
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{
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ptw32_oll_snziRoot_t proxyRoot;
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ptw32_oll_snziNode_t leafs[];
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};
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/*
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* FOLL lock support
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*/
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typedef struct ptw32_foll_node_t_ ptw32_foll_node_t;
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typedef struct ptw32_foll_local_t_ ptw32_foll_local_t;
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typedef struct ptw32_foll_rwlock_t_ ptw32_foll_rwlock_t;
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enum
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{
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ptw32_srwl_reader,
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ptw32_srwl_writer
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};
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enum
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{
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ptw32_srwl_free,
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ptw32_srwl_in_use
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};
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struct ptw32_foll_node_t_
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{
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ptw32_foll_node_t* qNextPtr;
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ptw32_oll_csnzi_t* csnziPtr;
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ptw32_foll_node_t* nextPtr;
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int kind;
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int allocState;
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BOOL spin;
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};
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struct ptw32_foll_local_t_
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{
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ptw32_foll_node_t* rNodePtr; // Default read node. Immutable
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ptw32_foll_node_t* wNodePtr; // Write node. Immutable.
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ptw32_foll_node_t* departFromPtr; // List node we last arrived at.
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ptw32_oll_ticket_t ticket; // C-SNZI ticket
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};
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struct ptw32_foll_rwlock_t_
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{
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ptw32_foll_node_t* tailPtr;
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ptw32_foll_node_t* rNodesPtr; // Head of reader node
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};
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/*
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* ShouldArriveAtTree() returns true if:
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* the compare_exchange in Arrive() fails too often under read access; or
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* ??
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* Note that this is measured across all access to
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* this lock, not just this attempt, so that highly
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* read-contended locks will use C-SNZI. Lightly
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* read-contended locks can reduce memory usage and some
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* processing by using the root directly.
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*/
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BOOL
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ptw32_oll_ShouldArriveAtTree()
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{
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return PTW32_FALSE;
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}
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size_t
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ptw32_oll_GetLeafForThread()
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{
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return 0;
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}
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/*
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* Only readers call ptw32_oll_Arrive()
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*
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* Checks whether the C-SNZI state is OPEN, and if so,
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* increments the surplus of the C-SNZI by either directly
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* arriving at the root node, or calling TreeArrive on one
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* of the leaf nodes. Returns a ticket pointing to the node
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* that was arrived at. If the state is CLOSED, makes no
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* change and returns a ticket that contains no pointer.
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*/
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ptw32_oll_ticket_t
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ptw32_oll_Arrive(ptw32_oll_csnzi_t* csnzi)
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{
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for (;;)
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{
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ptw32_oll_ticket_t ticket;
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ptw32_oll_snziRoot_t oldProxy = csnzi->proxyRoot;
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if (oldProxy.counter.internal.state != ptw32_oll_snziRoot_open)
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{
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ticket.snziNodeOrRoot.rootPtr = (ptw32_oll_snziRoot_t*)NULL;
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return ticket;
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}
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if (!ptw32_oll_ShouldArriveAtTree())
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{
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ptw32_oll_snziRoot_t newProxy = oldProxy;
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newProxy.counter.internal.count++;
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if (PTW32_INTERLOCKED_COMPARE_EXCHANGE_SIZE(
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(PTW32_INTERLOCKED_SIZEPTR)&csnzi->proxyRoot.counter,
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(PTW32_INTERLOCKED_SIZE)newProxy.counter.word,
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(PTW32_INTERLOCKED_SIZE)oldProxy.counter.word)
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== (PTW32_INTERLOCKED_SIZE)oldProxy.counter.word)
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{
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/* Exchange successful */
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ticket.snziNodeOrRoot.rootPtr = &csnzi->proxyRoot;
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return ticket;
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}
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}
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else
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{
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ptw32_oll_snziNode_t* leafPtr = &csnzi->leafs[ptw32_oll_GetLeafForThread()];
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ticket.snziNodeOrRoot.nodePtr = (ptw32_oll_TreeArrive(leafPtr) ? leafPtr : (ptw32_oll_snziNode_t*)NULL);
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return ticket;
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}
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}
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}
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/*
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* Decrements the C-SNZI surplus. Returns false iff the
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* resulting state is CLOSED and the surplus is zero.
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* Ticket must have been returned by an arrival. Must have
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* received this ticket from Arrive more times than Depart
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* has been called with the ticket. (Thus, the surplus
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* must be greater than zero.)
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*/
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BOOL
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ptw32_oll_Depart(ptw32_oll_ticket_t ticket)
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{
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return ptw32_oll_TreeDepart(ticket.snziNodeOrRoot);
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}
|
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/*
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* Increments the C-SNZI surplus and returns true if the
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* C-SNZI is open or has a surplus. Calls TreeArrive
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* recursively on the node’s parent if needed.
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* Otherwise, returns false without making any changes.
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*/
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BOOL
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ptw32_oll_TreeArrive(ptw32_oll_snziNodeOrRoot_t snziNodeOrRoot)
|
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{
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if (snziNodeOrRoot.nodePtr->counter.internal.root != ptw32_oll_snzi_root)
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{
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/* Non-root node */
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ptw32_oll_counter_t newCounter, oldCounter;
|
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BOOL arrivedAtParent = PTW32_FALSE;
|
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do
|
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{
|
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oldCounter = snziNodeOrRoot.nodePtr->counter;
|
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if (0 == oldCounter.internal.count && !arrivedAtParent)
|
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{
|
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if (ptw32_oll_TreeArrive(snziNodeOrRoot.nodePtr->parentPtr))
|
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arrivedAtParent = PTW32_TRUE;
|
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else
|
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return PTW32_FALSE;
|
||
}
|
||
newCounter = oldCounter;
|
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newCounter.internal.count++;
|
||
} while (PTW32_INTERLOCKED_COMPARE_EXCHANGE_SIZE(
|
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(PTW32_INTERLOCKED_SIZEPTR)&snziNodeOrRoot.nodePtr->counter,
|
||
(PTW32_INTERLOCKED_SIZE)newCounter.word,
|
||
(PTW32_INTERLOCKED_SIZE)oldCounter.word)
|
||
!= (PTW32_INTERLOCKED_SIZE)oldCounter.word);
|
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if (newCounter.internal.count != 0 && arrivedAtParent)
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ptw32_oll_TreeDepart(snziNodeOrRoot.nodePtr->parentPtr);
|
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return PTW32_TRUE;
|
||
}
|
||
else
|
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{
|
||
/* Root node */
|
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ptw32_oll_snziRoot_t newRoot, oldRoot;
|
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do
|
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{
|
||
oldRoot = *(ptw32_oll_snziRoot_t*)snziNodeOrRoot.rootPtr;
|
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if (oldRoot.counter.word == ptw32_oll_snziRoot_closedAndZero.counter.word)
|
||
return PTW32_FALSE;
|
||
newRoot = oldRoot;
|
||
newRoot.counter.internal.count++;
|
||
} while (PTW32_INTERLOCKED_COMPARE_EXCHANGE_SIZE(
|
||
(PTW32_INTERLOCKED_SIZEPTR)&snziNodeOrRoot.rootPtr->counter,
|
||
(PTW32_INTERLOCKED_SIZE)newRoot.counter.word,
|
||
(PTW32_INTERLOCKED_SIZE)oldRoot.counter.word)
|
||
!= (PTW32_INTERLOCKED_SIZE)oldRoot.counter.word);
|
||
return PTW32_TRUE;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Decrements the C-SNZI surplus, calling TreeDepart
|
||
* recursively on the node’s parent if needed. Returns
|
||
* false iff the resulting state of the C-SNZI is CLOSED
|
||
* and the surplus is zero. Otherwise, returns true.
|
||
*/
|
||
BOOL
|
||
ptw32_oll_TreeDepart(ptw32_oll_snziNodeOrRoot_t snziNodeOrRoot)
|
||
{
|
||
if (snziNodeOrRoot.nodePtr->counter.internal.root != ptw32_oll_snzi_root)
|
||
{
|
||
/* Non-root node */
|
||
ptw32_oll_counter_t newCounter, oldCounter;
|
||
do
|
||
{
|
||
newCounter = oldCounter = snziNodeOrRoot.nodePtr->counter;
|
||
newCounter.internal.count--;
|
||
} while (PTW32_INTERLOCKED_COMPARE_EXCHANGE_SIZE(
|
||
(PTW32_INTERLOCKED_SIZEPTR)&snziNodeOrRoot.nodePtr->counter,
|
||
(PTW32_INTERLOCKED_SIZE)newCounter.word,
|
||
(PTW32_INTERLOCKED_SIZE)oldCounter.word)
|
||
!= (PTW32_INTERLOCKED_SIZE)oldCounter.word);
|
||
return (0 == newCounter.internal.count)
|
||
? ptw32_oll_TreeDepart(snziNodeOrRoot.nodePtr->parentPtr)
|
||
: PTW32_TRUE;
|
||
}
|
||
else
|
||
{
|
||
/* Root node */
|
||
ptw32_oll_snziRoot_t newRoot, oldRoot;
|
||
do
|
||
{
|
||
newRoot = oldRoot = *(ptw32_oll_snziRoot_t*)snziNodeOrRoot.rootPtr;
|
||
newRoot.counter.internal.count--;
|
||
} while (PTW32_INTERLOCKED_COMPARE_EXCHANGE_SIZE(
|
||
(PTW32_INTERLOCKED_SIZEPTR)&snziNodeOrRoot.rootPtr->counter,
|
||
(PTW32_INTERLOCKED_SIZE)newRoot.counter.word,
|
||
(PTW32_INTERLOCKED_SIZE)oldRoot.counter.word)
|
||
!= (PTW32_INTERLOCKED_SIZE)oldRoot.counter.word);
|
||
return (newRoot.counter.word != ptw32_oll_snziRoot_closedAndZero.counter.word);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Opens a C-SNZI object. Requires C-SNZI state to be
|
||
* CLOSED and the surplus to be zero.
|
||
*/
|
||
void
|
||
ptw32_oll_Open(ptw32_oll_csnzi_t* csnziPtr)
|
||
{
|
||
csnziPtr->proxyRoot = ptw32_oll_snziRoot_openAndZero;
|
||
}
|
||
|
||
/*
|
||
* Opens a C-SNZI object while atomically performing count
|
||
* arrivals. Requires C-SNZI state to be CLOSED and
|
||
* the surplus to be zero.
|
||
*/
|
||
void
|
||
ptw32_oll_OpenWithArrivals(ptw32_oll_csnzi_t* csnziPtr, size_t count, BOOL close)
|
||
{
|
||
csnziPtr->proxyRoot.counter.internal.count = count;
|
||
csnziPtr->proxyRoot.counter.internal.state = (close ? ptw32_oll_snziRoot_closed : ptw32_oll_snziRoot_open);
|
||
}
|
||
|
||
/*
|
||
* Closes a C-SNZI object. Returns true iff the C-SNZI
|
||
* state changed from OPEN to CLOSED and the surplus is
|
||
* zero.
|
||
*/
|
||
BOOL
|
||
ptw32_oll_Close(ptw32_oll_csnzi_t* csnziPtr)
|
||
{
|
||
ptw32_oll_snziRoot_t newProxy, oldProxy;
|
||
do
|
||
{
|
||
oldProxy = csnziPtr->proxyRoot;
|
||
if (oldProxy.counter.internal.state != ptw32_oll_snziRoot_open)
|
||
{
|
||
return PTW32_FALSE;
|
||
}
|
||
newProxy = oldProxy;
|
||
newProxy.counter.internal.state = ptw32_oll_snziRoot_closed;
|
||
} while (PTW32_INTERLOCKED_COMPARE_EXCHANGE_SIZE(
|
||
(PTW32_INTERLOCKED_SIZEPTR)&csnziPtr->proxyRoot.counter,
|
||
(PTW32_INTERLOCKED_SIZE)newProxy.counter.word,
|
||
(PTW32_INTERLOCKED_SIZE)oldProxy.counter.word)
|
||
!= (PTW32_INTERLOCKED_SIZE)oldProxy.counter.word);
|
||
return (newProxy.counter.word == ptw32_oll_snziRoot_closedAndZero.counter.word);
|
||
}
|
||
|
||
/*
|
||
* Closes a C-SNZI if its surplus is zero. Otherwise, does
|
||
* nothing. Returns true iff C-SNZI state changed from
|
||
* OPEN to CLOSED.
|
||
*/
|
||
BOOL
|
||
ptw32_oll_CloseIfEmpty(ptw32_oll_csnzi_t* csnziPtr)
|
||
{
|
||
ptw32_oll_snziRoot_t newProxy, oldProxy;
|
||
do
|
||
{
|
||
oldProxy = csnziPtr->proxyRoot;
|
||
if (oldProxy.counter.word != ptw32_oll_snziRoot_openAndZero.counter.word)
|
||
{
|
||
return PTW32_FALSE;
|
||
}
|
||
newProxy = ptw32_oll_snziRoot_closedAndZero;
|
||
} while (PTW32_INTERLOCKED_COMPARE_EXCHANGE_SIZE(
|
||
(PTW32_INTERLOCKED_SIZEPTR)&csnziPtr->proxyRoot.counter,
|
||
(PTW32_INTERLOCKED_SIZE)newProxy.counter.word,
|
||
(PTW32_INTERLOCKED_SIZE)oldProxy.counter.word)
|
||
!= (PTW32_INTERLOCKED_SIZE)oldProxy.counter.word);
|
||
return PTW32_TRUE;
|
||
}
|
||
|
||
/*
|
||
* Returns whether the C-SNZI has a nonzero surplus and
|
||
* whether the C-SNZI is open.
|
||
* "nonZero" doesn't appear to be used anywhere in the algorithms.
|
||
*/
|
||
ptw32_oll_queryResult_t
|
||
ptw32_oll_Query(ptw32_oll_csnzi_t* csnziPtr)
|
||
{
|
||
ptw32_oll_queryResult_t query;
|
||
ptw32_oll_snziRoot_t proxy = csnziPtr->proxyRoot;
|
||
|
||
query.nonZero = (proxy.counter.internal.count > 0);
|
||
query.open = (proxy.counter.internal.state == ptw32_oll_snziRoot_open);
|
||
return query;
|
||
}
|
||
|
||
/*
|
||
* Returns whether the Arrive operation that returned
|
||
* the ticket succeeded.
|
||
*/
|
||
BOOL
|
||
ptw32_oll_Arrived(ptw32_oll_ticket_t t)
|
||
{
|
||
return (t.snziNodeOrRoot.nodePtr != NULL);
|
||
}
|
||
|
||
/*
|
||
* Constructs and returns a ticket that can be used to
|
||
* depart from the root node.
|
||
*/
|
||
ptw32_oll_ticket_t
|
||
ptw32_oll_DirectTicket(ptw32_oll_csnzi_t* csnziPtr)
|
||
{
|
||
ptw32_oll_ticket_t ticket;
|
||
ticket.snziNodeOrRoot.rootPtr = &csnziPtr->proxyRoot;
|
||
return ticket;
|
||
}
|
||
|
||
/* Scalable RW Locks */
|
||
|
||
typedef struct ptw32_srwl_rwlock_t_ ptw32_srwl_rwlock_t;
|
||
typedef struct ptw32_srwl_node_t_ ptw32_srwl_node_t;
|
||
typedef struct ptw32_srwl_local_t_ ptw32_srwl_local_t;
|
||
|
||
enum
|
||
{
|
||
ptw32_srwl_reader = 0,
|
||
ptw32_srwl_writer = 1
|
||
};
|
||
|
||
enum
|
||
{
|
||
ptw32_srwl_free = 0,
|
||
ptw32_srwl_in_use = 1
|
||
};
|
||
|
||
struct ptw32_srwl_rwlock_t_
|
||
{
|
||
ptw32_srwl_node_t* tailPtr;
|
||
ptw32_srwl_node_t* readerNodePtr;
|
||
};
|
||
|
||
struct ptw32_srwl_node_t_
|
||
{
|
||
ptw32_srwl_node_t* qNextPtr;
|
||
ptw32_oll_csnzi_t* csnziPtr;
|
||
ptw32_srwl_node_t* nextReaderPtr;
|
||
int kind; /* ptw32_srwl_reader, ptw32_srwl_writer */
|
||
int allocState; /* ptw32_srwl_free, ptw32_srwl_in_use */
|
||
BOOL spin;
|
||
};
|
||
|
||
/*
|
||
* When a ptw32_srwl_local_t is instantiated the "kind" of each of
|
||
* rNode and wNode must be set as appropriate. This is the only
|
||
* time "kind" is set.
|
||
*/
|
||
struct ptw32_srwl_local_t_
|
||
{
|
||
ptw32_srwl_node_t* rNodePtr;
|
||
ptw32_srwl_node_t* wNodePtr;
|
||
ptw32_srwl_node_t* departFromPtr;
|
||
ptw32_oll_ticket_t ticket;
|
||
};
|
||
|
||
/* Allocates a new reader node. */
|
||
ptw32_srwl_node_t*
|
||
ptw32_srwl_AllocReaderNode(ptw32_srwl_local_t* local)
|
||
{
|
||
ptw32_srwl_node_t* currNodePtr = local->rNodePtr;
|
||
for (;;)
|
||
{
|
||
if (currNodePtr->allocState == ptw32_srwl_free)
|
||
{
|
||
if (PTW32_INTERLOCKED_COMPARE_EXCHANGE_LONG(
|
||
(PTW32_INTERLOCKED_LONGPTR)&currNodePtr->allocState,
|
||
(PTW32_INTERLOCKED_LONG)ptw32_srwl_in_use,
|
||
(PTW32_INTERLOCKED_LONG)ptw32_srwl_free)
|
||
== (PTW32_INTERLOCKED_LONG)ptw32_srwl_in_use)
|
||
{
|
||
return currNodePtr;
|
||
}
|
||
}
|
||
currNodePtr = currNodePtr->next;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* Frees a reader node. Requires that its allocState
|
||
* is ptw32_srwl_in_use.
|
||
*/
|
||
void
|
||
ptw32_srwl_FreeReaderNode(ptw32_srwl_node_t* nodePtr)
|
||
{
|
||
nodePtr->allocState := ptw32_srwl_free;
|
||
}
|
||
|
||
void
|
||
ptw32_srwl_WriterLock(ptw32_srwl_rwlock_t* lockPtr, ptw32_srwl_local_t* localPtr)
|
||
{
|
||
oldTailPtr = (ptw32_srwl_rwlock_t*)PTW32_INTERLOCKED_EXCHANGE_PTR(
|
||
(PTW32_INTERLOCKED_PVOID_PTR)&lockPtr->tailPtr,
|
||
(PTW32_INTERLOCKED_PVOID)localPtr->wNodePtr);
|
||
if (oldTailPtr != NULL)
|
||
{
|
||
localPtr->wNodePtr->spin := PTW32_TRUE;
|
||
oldTailPtr->qNextPtr = localPtr->wNodePtr;
|
||
if (oldTailPtr->kind == ptw32_srwl_writer)
|
||
{
|
||
while (localPtr->wNodePtr->spin);
|
||
}
|
||
else
|
||
{
|
||
/* Wait until node is properly recycled */
|
||
while (ptw32_oll_Query(oldTailPtr->csnzi).open);
|
||
/*
|
||
* Close C-SNZI of previous reader node.
|
||
* If there are no readers to signal us, spin on
|
||
* previous node and free it before entering
|
||
* critical section.
|
||
*/
|
||
if (ptw32_oll_Close(oldTailPtr->csnzi))
|
||
{
|
||
while (oldTailPtr->spin);
|
||
ptw32_srwl_FreeReaderNode(oldTailPtr);
|
||
}
|
||
else
|
||
{
|
||
while (localPtr->wNodePtr->spin);
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
void
|
||
ptw32_srwl_WriterUnlock(ptw32_srwl_rwlock_t* lockPtr, ptw32_srwl_local_t* localPtr)
|
||
{
|
||
if (localPtr->wNodePtr->qNextPtr == NULL)
|
||
{
|
||
if (PTW32_INTERLOCKED_COMPARE_EXCHANGE_PTR(
|
||
(PTW32_INTERLOCKED_PVOIDPTR)&lockPtr->tailPtr,
|
||
(PTW32_INTERLOCKED_PVOID)NULL,
|
||
(PTW32_INTERLOCKED_PVOID)localPtr->wNodePtr)
|
||
== (PTW32_INTERLOCKED_PVOID)NULL)
|
||
{
|
||
return;
|
||
}
|
||
else
|
||
{
|
||
while (localPtr->wNodePtr->qNextPtr == NULL);
|
||
}
|
||
}
|
||
/* Clean up */
|
||
localPtr->wNodePtr->qNextPtr->spin = PTW32_FALSE;
|
||
localPtr->wNodePtr->qNextPtr = NULL;
|
||
}
|
||
|
||
void
|
||
ptw32_srwl_ReaderLock(ptw32_srwl_rwlock_t* lockPtr, ptw32_srwl_local_t* localPtr)
|
||
{
|
||
ptw32_srwl_node_t* rNodePtr = NULL;
|
||
for (;;)
|
||
{
|
||
ptw32_srwl_node_t* tailPtr = lockPtr->tailPtr;
|
||
/* If no nodes are in the queue */
|
||
if (tailPtr == NULL)
|
||
{
|
||
if (rNodePtr == NULL)
|
||
{
|
||
rNodePtr = ptw32_srwl_AllocReaderNode(localPtr);
|
||
}
|
||
rNodePtr->spin = PTW32_FALSE;
|
||
if (PTW32_INTERLOCKED_COMPARE_EXCHANGE_PTR(
|
||
(PTW32_INTERLOCKED_PVOIDPTR)&lockPtr->tailPtr,
|
||
(PTW32_INTERLOCKED_PVOID)rNodePtr,
|
||
(PTW32_INTERLOCKED_PVOID)NULL)
|
||
== (PTW32_INTERLOCKED_PVOID)rNodePtr)
|
||
{
|
||
ptw32_oll_Open(rNodePtr->csnzi);
|
||
localPtr->ticket = ptw32_oll_Arrive(rNodePtr->csnzi);
|
||
if (ptw32_oll_Arrived(localPtr->ticket))
|
||
{
|
||
localPtr->departFromPtr = rNodePtr;
|
||
return;
|
||
}
|
||
/* Avoid reusing inserted node */
|
||
rNodePtr = NULL;
|
||
}
|
||
}
|
||
/* Otherwise, there is a node in the queue */
|
||
else
|
||
{
|
||
/* Is last node a writer node? */
|
||
if (tailPtr->kind == ptw32_srwl_writer)
|
||
{
|
||
if (rNodePtr == NULL)
|
||
{
|
||
rNodePtr = ptw32_srwl_AllocReaderNode(localPtr);
|
||
}
|
||
rNodePtr->spin = PTW32_TRUE;
|
||
if (PTW32_INTERLOCKED_COMPARE_EXCHANGE_PTR(
|
||
(PTW32_INTERLOCKED_PVOIDPTR)&lockPtr->tailPtr,
|
||
(PTW32_INTERLOCKED_PVOID)rNodePtr,
|
||
(PTW32_INTERLOCKED_PVOID)tailPtr)
|
||
== (PTW32_INTERLOCKED_PVOID)rNodePtr)
|
||
{
|
||
tailPtr->qNextPtr = rNodePtr;
|
||
localPtr->ticket = ptw32_oll_Arrive(rNodePtr->csnzi);
|
||
if (ptw32_oll_Arrived(localPtr->ticket))
|
||
{
|
||
localPtr->departFromPtr = rNodePtr;
|
||
while (rNodePtr->spin);
|
||
return;
|
||
}
|
||
/* Avoid reusing inserted node */
|
||
rNodePtr = NULL;
|
||
}
|
||
}
|
||
/*
|
||
* Otherwise, last node is a reader node.
|
||
* (tailPtr->kind == ptw32_srwl_reader)
|
||
*/
|
||
else
|
||
{
|
||
localPtr->ticket = ptw32_oll_Arrive(tailPtr->csnzi);
|
||
if (ptw32_oll_Arrived(localPtr->ticket))
|
||
{
|
||
if (rNodePtr != NULL)
|
||
{
|
||
ptw32_srwl_FreeReaderNode(rNodePtr);
|
||
}
|
||
localPtr->departFromPtr = tailPtr;
|
||
while (tailPtr->spin);
|
||
return;
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
void
|
||
ptw32_srwl_ReaderUnlock(ptw32_srwl_rwlock_t* lockPtr, ptw32_srwl_local_t* localPtr)
|
||
{
|
||
if (ptw32_oll_Depart(localPtr->departFromPtr->csnzi, localPtr->ticket))
|
||
{
|
||
return;
|
||
}
|
||
/* Clean up */
|
||
localPtr->departFromPtr->qNextPtr->spin = PTW32_FALSE;
|
||
localPtr->departFromPtr->qNextPtr = NULL;
|
||
ptw32_srwl_FreeReaderNode(localPtr->departFromPtr);
|
||
}
|
||
|
||
|
||
#include <stdio.h>
|
||
|
||
int main()
|
||
{
|
||
printf("%lx\n", PTW32_OLL_MAXREADERS);
|
||
return 0;
|
||
}
|
||
|