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Full Discussion: pthread_mutex_lock in ANSI C vs using Atomic builtins of GCC
Top Forums Programming pthread_mutex_lock in ANSI C vs using Atomic builtins of GCC Post 302448266 by sehang on Wednesday 25th of August 2010 03:39:54 PM
Old 08-25-2010
pthread_mutex_lock in ANSI C vs using Atomic builtins of GCC
I have a program which has 7-8 threads, and lots of shared variables; these variables (and also they may not the primitive type, they may be enum or struct ), then they may read/write by different threads at the same time.

Now, my design is like this,

Code:
typedef unsigned short int UINT16;
struct STRUCT {
  UINT16 uint16;
  int INT;
}
enum ENUM = { ... };

/* Shared Variables. */
struct STRUCT Shared_VariableA;
enum ENUM Shared_VariableB;

UINT16 GetVA () {
    pthread_mutex_lock( &_L_LOCK );
        UINT16 TMP = Shared_VariableA.uint16;
    pthread_mutex_lock( &_L_LOCK );
    return TMP;
}

void SetVA ( UINT16 in ) {
     pthread_mutex_lock( &_L_LOCK );
         Shared_VariableA.uint16 = in;
     pthread_mutex_lock( &_L_LOCK );
 }

Is it enough to guarantee that only a thread can write/read shared variables at the same time?

How about the following method? Same?
From the reference : Techie Stuff Atomic Operations

Code:
/* Initialization. */
atomic_t uint16 = ATOMIC_INIT ( 0 );

UINT16 GetVA () {
         UINT16 TMP = atomic_read( &uint16 );  /* Force convert 'int' to UINT16 since atomic_read() returns an int (32 bits). */
        return TMP;
 }
 
 void SetVA ( UINT16 in ) {
       atomic_set( &uint16,in );
  }

Whether getVA() will return an arbitrary value when SetVA() is running by other threads?
 

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LEARN ABOUT OPENSOLARIS

tiffsetfield

TIFFSetField(3tiff)													       TIFFSetField(3tiff)

NAME

       TIFFSetField, TIFFVSetField - set the value(s) of a tag in a TIFF file open for writing

SYNOPSIS

       #include <tiffio.h>
       int TIFFSetField(TIFF* tif, ttag_t tag, ...)
       #include <stdarg.h>
       int TIFFVSetField(TIFF* tif, ttag_t tag, va_list ap)

       TIFFSetField sets the value of a field or pseudo-tag in the current directory associated with the open TIFF file. A pseudo-tag is a parame-
       ter that is used to control the operation of the TIFF library but whose value is not read or written to the underlying file.

       To set the value of a field, the file must have been previously opened for writing with TIFFOpen(3tiff). Pseudo-tags can be set whether the
       file was opened for reading or writing.

       The field is identified by tag, one of the values defined in the include file tiff.h (see also the table below). The actual value is speci-
       fied using a variable argument list as prescribed by the stdarg(3) interface, or, on some machines, the varargs(3) interface.

EXTENDED DESCRIPTION

       TIFFVSetField is functionally equivalent to TIFFSetField except that TIFFVSetField takes a pointer to a variable argument  list.  TIFFVSet-
       Field is useful for writing routines that are layered on top of the functionality provided by TIFFSetField.

       The  tags  understood by libtiff, the number of parameter values, and the expected types for the parameter values are shown below. The data
       types are as follows:

       char*

	   Null-terminated string, corresponds to the ASCII data type

       uint16

	   Unsigned 16-bit value

       uint32

	   Unsigned 32-bit value

       uint16*

	   Array of unsigned 16-bit values

       void*

	   Array of data values of unspecified type

       Consult the TIFF specification for information on the meaning of each tag.

       +-------------------------------+----------------+-----------------+------------------------------+
       |TAG NAME		       | COUNT		| TYPES 	  | NOTES			 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_ARTIST		       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_BADFAXLINES	       | 1		| uint32	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_BITSPERSAMPLE	       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_CLEANFAXDATA	       | 1		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_COLORMAP	       | 3		| uint16*	  | 1<<BitsPerSample arrays	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_COMPRESSION	       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_CONSECUTIVEBADFAXLINES | 1		| uint32	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_DATETIME	       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_DOCUMENTNAME	       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_DOTRANGE	       | 2		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_EXTRASAMPLES	       | 2		| uint16,uint16*  | -- count and types array	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_FAXMODE 	       | 1		| int		  | -- G3/G4 compression pseudo- |
       |			       |		|		  | tag 			 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_FAXFILLFUNC	       | 1		| TIFFFaxFillFunc | G3/G4 compression pseudo-tag |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_FILLORDER	       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_GROUP3OPTIONS	       | 1		| uint32	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_GROUP4OPTIONS	       | 1		| uint32	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_HALFTONEHINTS	       | 2		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_HOSTCOMPUTER	       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_IMAGEDEPTH	       | 1		| uint32	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_IMAGEDESCRIPTION       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_IMAGELENGTH	       | 1		| uint32	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_IMAGEWIDTH	       | 1		| uint32	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_INKNAMES	       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_INKSET		       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_JPEGTABLES	       | 2		| uint32*,void*   | -- count and tables 	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_JPEGQUALITY	       | 1		| int		  | JPEG pseudo-tag		 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_JPEGCOLORMODE	       | 1		| int		  | -- JPEG pseudo-tag		 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_JPEGTABLESMODE	       | 1		| int		  | -- JPEG pseudo-tag		 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_MAKE		       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_MATTEING	       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_MAXSAMPLEVALUE	       | 1		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_MINSAMPLEVALUE	       | 1		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_MODEL		       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_ORIENTATION	       | 1		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_PAGENAME	       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_PAGENUMBER	       | 2		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_PHOTOMETRIC	       | 1		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_PLANARCONFIG	       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_PREDICTOR	       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_PRIMARYCHROMACITIES    | 1		| float*	  | 6-entry array		 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_REFERENCEBLACKWHITE    | 1		| float*	  | - 2*SamplesPerPixel array	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_RESOLUTIONUNIT	       | 1		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_ROWSPERSTRIP	       | 1		| uint32	  | -- must be greater than 0	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_SAMPLEFORMAT	       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_SAMPLESPERPIXEL        | 1		| uint16	  | -- value must be <= 4	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_SMAXSAMPLEVALUE        | 1		| double	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_SMINSAMPLEVALUE        | 1		| double	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_SOFTWARE	       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_STONITS 	       | 1		| double	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_SUBFILETYPE	       | 1		| uint32	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_SUBIFD		       | 2		| uint16,uint32*  | count and offsets array	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_TARGETPRINTER	       | 1		| char* 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_THRESHOLDING	       | 1		| uint16	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_TILEDEPTH	       | 1		| uint32	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_TILELENGTH	       | 1		| uint32	  | -- must be a multiple of 8	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_TILEWIDTH	       | 1		| uint32	  | -- must be a multiple of 8	 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_TRANSFERFUNCTION       | 1 or 3=	| uint16*	  | 1<<BitsPerSample	   entry |
       |			       |		|		  | arrays			 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_WHITEPOINT	       | 1		| float*	  | 2-entry array		 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_XPOSITION	       | 1		| float 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_XRESOLUTION	       | 1		| float 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_YCBCRCOEFFICIENTS      | 1		| float*	  | - 3-entry array		 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_YCBCRPOSITIONING       | 1		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_YCBCRSUBSAMPLING       | 2		| uint16	  | --				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_YPOSITION	       | 1		| float 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_YRESOLUTION	       | 1		| float 	  |				 |
       +-------------------------------+----------------+-----------------+------------------------------+
       |TIFFTAG_ICCPROFILE	       | 2		| uint32,void*	  | count, profile data+	 |
       +-------------------------------+----------------+-----------------+------------------------------+

       -		       Tag may not have its values changed once data is written.

       =		       If SamplesPerPixel is 1, then a single array is passed. Otherwise, three arrays should be passed.

       +		       The contents of this field are quite complex. See The ICC Profile Format Specification, Annex B "Embedding ICC Pro-
			       files in TIFF Files", available at http://www.color.org, for an explanation.

   Diagnostics
       All error messages are directed to the TIFFError(3tiff) routine.

       %s: Cannot modify tag "%Datahihaswralready  been  written  to  the  file, so the specified tag value cannot be changed. This restriction is
			       applied to all tags that affect the format of written data.

       %d: Bad value for "%s". An invalid value was supplied for the named tag.

       1 is returned if the tag is defined in the current directory. Otherwise, 0 is returned.

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWTiff			   |
       +-----------------------------+-----------------------------+
       |Interface stability	     |Uncommitted		   |
       +-----------------------------+-----------------------------+

       libtiff(3), TIFFOpen(3tiff), TIFFGetField(3tiff), TIFFSetDirectory(3tiff), TIFFReadDirectory(3tiff), TIFFWriteDirectory(3tiff)

       This man page was originally written by Sam Leffler. Updated by Breda McColgan, Sun Microsystems Inc., 2004.

								    05 Apr 2004 					       TIFFSetField(3tiff)
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