Addition of an arbitary bitmask handling set of functions
New memory deallocation routines for the DCBS
This commit is contained in:
Mark Riddoch
@ -19,6 +19,7 @@
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*/
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#include <spinlock.h>
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#include <buffer.h>
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#include <gwbitmask.h>
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struct session;
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struct server;
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@ -87,6 +88,29 @@ typedef struct dcbstats {
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int n_buffered; /**< Number of buffered writes */
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} DCBSTATS;
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/**
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* The data structure that is embedded witin a DCB and manages the complex memory
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* management issues of a DCB.
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*
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* The DCB structures are used as the user data within the polling loop. This means that
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* polling threads may aschronously wake up and access these structures. It is not possible
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* to simple remove the DCB from the epoll system and then free the data, as every thread
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* that is currently running an epoll call must wake up and re-issue the epoll_wait system
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* call, the is the only way we can be sure that no polling thread is pending a wakeup or
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* processing an event that will access the DCB.
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*
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* We solve this issue by making the dcb_free routine merely mark a DCB as a zombie and
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* place it on a special zombie list. Before placing the DCB on the zombie list we create
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* a bitmask with a bit set in it for each active polling thread. Each thread will call
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* a routine to process the zombie list at the end of the polling loop. This routine
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* will clear the bit value that corresponds to the calling thread. Once the bitmask
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* is completely cleared the DCB can finally be freed and removed from the zombie list.
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*/
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typedef struct {
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GWBITMASK bitmask; /**< The bitmask of threads */
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struct dcb *next; /**< Next pointer for the zombie list */
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} DCBMM;
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/**
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* Descriptor Control Block
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*
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@ -114,6 +138,7 @@ typedef struct dcb {
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struct dcb *next; /**< Next DCB in the chain of allocated DCB's */
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struct service *service; /**< The related service */
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void *data; /**< Specific client data */
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DCBMM memdata; /**< The data related to DCB memory management */
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} DCB;
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/* DCB states */
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@ -124,10 +149,12 @@ typedef struct dcb {
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#define DCB_STATE_LISTENING 5 /**< The DCB is for a listening socket */
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#define DCB_STATE_DISCONNECTED 6 /**< The socket is now closed */
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#define DCB_STATE_FREED 7 /**< Memory freed */
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#define DCB_STATE_ZOMBIE 8 /**< DCB is no longer active, waiting to free it */
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/* A few useful macros */
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#define DCB_SESSION(x) (x)->session
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#define DCB_PROTOCOL(x, type) (type *)((x)->protocol)
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#define DCB_ISZOMBIE(x) ((x)->state == DCB_STATE_ZOMBIE)
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extern DCB *dcb_alloc(); /* Allocate a DCB */
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extern void dcb_free(DCB *); /* Free a DCB */
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@ -136,6 +163,7 @@ extern int dcb_read(DCB *, GWBUF **); /* Generic read routine */
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extern int dcb_write(DCB *, GWBUF *); /* Generic write routine */
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extern int dcb_drain_writeq(DCB *); /* Generic write routine */
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extern void dcb_close(DCB *); /* Generic close functionality */
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extern void dcb_process_zombies(int); /* Process Zombies */
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extern void printAllDCBs(); /* Debug to print all DCB in the system */
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extern void printDCB(DCB *); /* Debug print routine */
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extern void dprintAllDCBs(DCB *); /* Debug to print all DCB in the system */
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52
include/gwbitmask.h
Normal file
52
include/gwbitmask.h
Normal file
@ -0,0 +1,52 @@
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#ifndef _GWBITMASK_H
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#define _GWBITMASK_H
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/*
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* This file is distributed as part of the SkySQL Gateway. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program 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 FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright SkySQL Ab 2013
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*/
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#include <spinlock.h>
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/**
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* @file gwbitmask.h An implementation of an arbitarly long bitmask
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*
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* @verbatim
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* Revision History
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*
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* Date Who Description
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* 28/06/13 Mark Riddoch Initial implementation
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*
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* @endverbatim
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*/
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#define BIT_LENGTH_INITIAL 32 /**< Initial number of bits in the bitmask */
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#define BIT_LENGTH_INC 32 /**< Number of bits to add on each increment */
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/**
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* The bitmask structure used to store an arbitary large bitmask
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*/
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typedef struct {
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SPINLOCK lock; /**< Lock to protect the bitmask */
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unsigned char *bits; /**< Pointer to the bits themselves */
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unsigned int length; /**< The number of bits in the bitmask */
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} GWBITMASK;
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extern void bitmask_init(GWBITMASK *);
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extern void bitmask_set(GWBITMASK *, int);
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extern void bitmask_clear(GWBITMASK *, int);
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extern int bitmask_isset(GWBITMASK *, int);
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extern int bitmask_isallclear(GWBITMASK *);
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extern void bitmask_copy(GWBITMASK *, GWBITMASK *);
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#endif
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@ -18,6 +18,7 @@
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* Copyright SkySQL Ab 2013
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*/
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#include <dcb.h>
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#include <gwbitmask.h>
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/**
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* @file poll.h The poll related functionality
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@ -33,10 +34,11 @@
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#define MAX_EVENTS 1000
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#define EPOLL_TIMEOUT 1000 /**< The epoll timeout we use (milliseconds) */
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extern void poll_init();
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extern int poll_add_dcb(DCB *);
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extern int poll_remove_dcb(DCB *);
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extern void poll_waitevents();
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extern void poll_shutdown();
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extern void dprintPollStats(DCB *);
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extern void poll_init();
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extern int poll_add_dcb(DCB *);
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extern int poll_remove_dcb(DCB *);
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extern void poll_waitevents(void *);
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extern void poll_shutdown();
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extern GWBITMASK *poll_bitmask();
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extern void dprintPollStats(DCB *);
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#endif
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@ -19,10 +19,19 @@
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*/
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#include <pthread.h>
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/**
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* @file thread.h The gateway threading interface
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*
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* An encapsulation of the threading used by the gateway. This is designed to
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* isolate the majority of the gateway code from th epthread library, enabling
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* the gateway to be ported to a different threading package with the minimum
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* of changes.
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*/
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#define THREAD pthread_t
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#define THREAD_SHELF pthread_self
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extern void *thread_start(void (*entry)());
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extern void *thread_start(void (*entry)(void *), void *arg);
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extern void thread_wait(void *thd);
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#endif
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