Using thread local variables instead of the global ones

Fri Apr 28 07:45:19 EDT 2006

Steve, Frank

Both of you are in right.

The primary aim would be to eliminate the need of the
unnecessary locks around the processwide global variables. 
It may dissolve the pool of threads resposible for serving
the user requests.

I agree with Steve in that using thread locals is just a
makeshift it would be desirable to eliminate the processwide
globals at all.

The storage specifier would be an easy way to rewrite the
existing code but Frank's note is a bit diappointing. As far
as I know __tread with gcc can do handle this problem. Maybe
Microsoft will reach this level until the end of this
decade. Using the Win TLS API would be more complicated but
not impossible to use. However the number of the TLS slots
are limited depending on the operating system.

At a first sight i have found *only* the following problems
in the core mapserver code. Some of the variables contain
invariant data and therefore not to be guarded.

\mapserver\epplib.c(47):static int REVERSE; /* set to 1 on
bigendian machines */

\mapserver\mapcpl.c(57):static char    
szStaticResult[MS_PATH_BUF_SIZE];

\mapserver\maperror.c(110):static char
*ms_errorCodes[MS_NUMERRORCODES] = {"",
\mapserver\maperror.c(154):    static errorObj ms_error =
{MS_NOERR, "", "", NULL};
\mapserver\maperror.c(169):static te_info_t *error_list = NULL;
\mapserver\maperror.c(552):  static char version[1024];
\mapserver\maperror.c(651):    static char nonblocking_set = 0;

\mapserver\mapfile.c(178):static char *msUnits[7]={"INCHES",
"FEET", "MILES", "METERS", "KILOMETERS", "DD", "PIXELS"};
\mapserver\mapfile.c(179):static char
*msLayerTypes[8]={"POINT", "LINE", "POLYGON", "RASTER",
"ANNOTATION", "QUERY", "CIRCLE", "TILEINDEX"};
\mapserver\mapfile.c(182):static char
*msBitmapFontSizes[5]={"TINY", "SMALL", "MEDIUM", "LARGE",
"GIANT"};
\mapserver\mapfile.c(183):static char
*msQueryMapStyles[4]={"NORMAL", "HILITE", "SELECTED",
"INVERTED"};
\mapserver\mapfile.c(184):static char *msStatus[5]={"OFF",
"ON", "DEFAULT", "EMBED"};
\mapserver\mapfile.c(186):static char
*msTrueFalse[2]={"FALSE", "TRUE"};
\mapserver\mapfile.c(188):static char
*msJoinType[2]={"ONE-TO-ONE", "ONE-TO-MANY"};

\mapserver\mapgd.c(236):static unsigned char PNGsig[8] =
{137, 80, 78, 71, 13, 10, 26, 10}; /* 89 50 4E 47 0D 0A 1A
0A hex */
\mapserver\mapgd.c(237):static unsigned char JPEGsig[3] =
{255, 216, 255}; /* FF D8 FF hex */
\mapserver\mapgd.c(908):  static gdPoint points[38];
\mapserver\mapgd.c(2425):  static double last_style_size;
\mapserver\mapgd.c(2716):  static int styleIndex, styleVis;
\mapserver\mapgd.c(2717):  static double styleSize=0,
styleCoef=0, last_style_size=-1;
\mapserver\mapgd.c(2718):  static int last_style_c=-1,
last_style_stylelength=-1, last_styleVis=0;

\mapserver\mapgdal.c(141):static int    bGDALInitialized = 0;

\mapserver\mapgeos.cpp(98):GeometryFactory *gf=NULL; 

\mapserver\maphttp.c(140):static int gbCurlInitialized =
MS_FALSE;
\mapserver\mapimagemap.c(141):static char *layerlist=NULL;
\mapserver\mapimagemap.c(142):static int layersize=0;
\mapserver\mapimagemap.c(143):static pString imgStr,
layerStr={ &layerlist, &layersize, 0 };
\mapserver\mapimagemap.c(146):static const char
*polyHrefFmt, *polyMOverFmt, *polyMOutFmt;
\mapserver\mapimagemap.c(147):static const char
*symbolHrefFmt, *symbolMOverFmt, *symbolMOutFmt;
\mapserver\mapimagemap.c(148):static const char *mapName;
\mapserver\mapimagemap.c(150):static int suppressEmpty=0;
\mapserver\mapimagemap.c(229):static int lastcolor=-1;
\mapserver\mapimagemap.c(273):static char* lname;
\mapserver\mapimagemap.c(274):static int dxf;

\mapserver\mapio.c(67):static int is_msIO_initialized =
MS_FALSE;
\mapserver\mapio.c(69):static msIOContext default_stdin_context;
\mapserver\mapio.c(70):static msIOContext
default_stdout_context;
\mapserver\mapio.c(71):static msIOContext
default_stderr_context;
\mapserver\mapio.c(73):static msIOContext current_stdin_context;
\mapserver\mapio.c(74):static msIOContext
current_stdout_context;
\mapserver\mapio.c(75):static msIOContext
current_stderr_context;

\mapserver\maplexer.c(220):static YY_BUFFER_STATE
yy_current_buffer = 0;
\mapserver\maplexer.c(230):static char yy_hold_char;
\mapserver\maplexer.c(232):static int yy_n_chars;		/* number
of characters read into yy_ch_buf */
\mapserver\maplexer.c(238):static char *yy_c_buf_p = (char *) 0;
\mapserver\maplexer.c(239):static int yy_init = 1;		/*
whether we need to initialize */
\mapserver\maplexer.c(240):static int yy_start = 0;	/* start
state number */
\mapserver\maplexer.c(306):static yyconst short int
yy_accept[2406] =
\mapserver\maplexer.c(575):static yyconst int yy_ec[256] =
\mapserver\maplexer.c(607):static yyconst int yy_meta[52] =
\mapserver\maplexer.c(617):static yyconst short int
yy_base[2420] =
\mapserver\maplexer.c(887):static yyconst short int
yy_def[2420] =
\mapserver\maplexer.c(1157):static yyconst short int
yy_nxt[2740] =
\mapserver\maplexer.c(1462):static yyconst short int
yy_chk[2740] =
\mapserver\maplexer.c(1767):static yy_state_type
yy_last_accepting_state;
\mapserver\maplexer.c(1768):static char *yy_last_accepting_cpos;
\mapserver\maplexer.c(1866):static int yy_start_stack_ptr = 0;
\mapserver\maplexer.c(1867):static int yy_start_stack_depth = 0;
\mapserver\maplexer.c(1868):static int *yy_start_stack = 0;
\mapserver\mapmygis.c(245):static int gBYTE_ORDER = 0;

\mapserver\mapogcsos.c(1974):    static char *request=NULL,
*service=NULL;

\mapserver\mapogr.cpp(840):static int bOGRDriversRegistered
= MS_FALSE;

\mapserver\mapows.c(1647):  static char epsgCode[20] ="";

\mapserver\mapparser.c(282):static const unsigned char
yytranslate[] =
\mapserver\mapparser.c(317):static const unsigned char
yyprhs[] =
\mapserver\mapparser.c(328):static const yysigned_char yyrhs[] =
\mapserver\mapparser.c(354):static const unsigned short
yyrline[] =
\mapserver\mapparser.c(368):static const char *const yytname[] =
\mapserver\mapparser.c(381):static const unsigned short
yytoknum[] =
\mapserver\mapparser.c(391):static const unsigned char yyr1[] =
\mapserver\mapparser.c(402):static const unsigned char yyr2[] =
\mapserver\mapparser.c(415):static const unsigned char
yydefact[] =
\mapserver\mapparser.c(431):static const yysigned_char
yydefgoto[] =
\mapserver\mapparser.c(439):static const short yypact[] =
\mapserver\mapparser.c(455):static const yysigned_char
yypgoto[] =
\mapserver\mapparser.c(465):static const unsigned char
yytable[] =
\mapserver\mapparser.c(491):static const yysigned_char
yycheck[] =
\mapserver\mapparser.c(519):static const unsigned char
yystos[] =

\mapserver\mappluginlayer.c(46):static VTFactoryObj
gVirtualTableFactory = {MS_MAXLAYERS, 0, {NULL}};

\mapserver\mappool.c(206):static int connectionCount = 0;
\mapserver\mappool.c(207):static int connectionMax = 0;
\mapserver\mappool.c(208):static connectionObj *connections
= NULL;

\mapserver\mapproject.c(889):static char *ms_proj_lib = NULL;
\mapserver\mapproject.c(890):static char *last_filename = NULL;
\mapserver\mapproject.c(918):    static int finder_installed
= 0;

\mapserver\mapscale.c(68):static char *unitText[5]={"in",
"ft", "mi", "m", "km"};
\mapserver\mapscale.c(69):double inchesPerUnit[6]={1, 12,
63360.0, 39.3701, 39370.1, 4374754};

\mapserver\mapsde.c(216):static int lcacheCount = 0;
\mapserver\mapsde.c(217):static int lcacheMax = 0;
\mapserver\mapsde.c(218):static layerId *lcache = NULL;

\mapserver\mapshape.c(70):static int      bBigEndian;

\mapserver\mapsvg.c(164):    static char epsgCode[20] ="";
\mapserver\mapsvg.c(165):    static char *value;

\mapserver\mapswf.c(97):static char gszFilename[128];
\mapserver\mapswf.c(98):static char gszAction[256];
\mapserver\mapswf.c(99):static char gszTmp[256];

\mapserver\mapsymbol.c(151):static char
*msCapsJoinsCorners[7]={"NONE", "BEVEL", "BUTT", "MITER",
"ROUND", "SQUARE", "TRIANGLE"};

\mapserver\mapthread.c(196):static int thread_debug = 0;
\mapserver\mapthread.c(198):static char *lock_names[] = 
\mapserver\mapthread.c(213):static int mutexes_initialized = 0;
\mapserver\mapthread.c(214):static pthread_mutex_t
mutex_locks[TLOCK_MAX];
\mapserver\mapthread.c(223):    static pthread_mutex_t
core_lock = PTHREAD_MUTEX_INITIALIZER;
\mapserver\mapthread.c(294):static int mutexes_initialized = 0;
\mapserver\mapthread.c(295):static HANDLE
mutex_locks[TLOCK_MAX];
\mapserver\mapthread.c(305):    static HANDLE core_lock = NULL;

\mapserver\maputil.c(1068):static int tmpCount = 0;
\mapserver\maputil.c(1069):static char *ForcedTmpBase = NULL;

\mapserver\mapwms.c(249):static char *wms_exception_format=NULL;
\mapserver\mapwms.c(2779):  static char *request=NULL,
*service=NULL, *format=NULL;

\mapserver\md5c.c(58):static unsigned char PADDING[64] = {

\mapserver\strptime.c(43):static const char *abb_weekdays[] = {
\mapserver\strptime.c(54):static const char *full_weekdays[] = {
\mapserver\strptime.c(65):static const char *abb_month[] = {
\mapserver\strptime.c(81):static const char *full_month[] = {
\mapserver\strptime.c(97):static const char *ampm[] = {

\mapserver\gdft\gdkanji.c(103):	static int whatcode;
\mapserver\gdft\gdkanji.c(403):	static unsigned char
tmp[BUFSIZ];
\mapserver\gdft\gdkanji.c(489):	static unsigned char
tmp_dest[BUFSIZ];

\mapserver\gdft\gdttf.c(712):  static gdCache_head_t
*tweenColorCache=NULL; /****** set up tweenColorCache on
first call ************/
\mapserver\gdft\gdttf.c(852):  static gdCache_head_t
*fontCache=NULL; /****** initialize font engine on first
call ************/
\mapserver\gdft\gdttf.c(853):  static TT_Engine 	engine;
\mapserver\gdft\jisx0208.h(7):static unsigned short
UnicodeTbl[][94] = {

The mostly used related libraries like GD should also be
reviewed.

Tamas

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