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diff --git a/doc/rrdthreads.txt b/doc/rrdthreads.txt
index 21ed7927095c35df76f18ebdd053e4f11c3e2b2f..43bd697a3dc498a544eb9db78184bff7dc7d53f2 100644 (file)
--- a/doc/rrdthreads.txt
+++ b/doc/rrdthreads.txt
multi-threaded programs
S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
- Using librrd in multi-threaded programs requires some extra precau-
- tions, as the RRD library in its original form was not thread-safe at
- all. This document describes requirements and pitfalls on the way to
- use the multi-threaded version of librrd in your own programs. It also
- gives hints for future RRD development to keep the library thread-safe.
+ Using librrd in multi-threaded programs requires some extra
+ precautions, as the RRD library in its original form was not thread-
+ safe at all. This document describes requirements and pitfalls on the
+ way to use the multi-threaded version of librrd in your own programs.
+ It also gives hints for future RRD development to keep the library
+ thread-safe.
Currently only some RRD operations are implemented in a thread-safe
way. They all end in the usual ""_r"" suffix.
D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
In order to use librrd in multi-threaded programs you must:
- · Link with _\bl_\bi_\bb_\br_\br_\bd_\b__\bt_\bh instead of _\bl_\bi_\bb_\br_\br_\bd (use "-lrrd_th" when linking)
+ · Link with _\bl_\bi_\bb_\br_\br_\bd_\b__\bt_\bh instead of _\bl_\bi_\bb_\br_\br_\bd (use "-lrrd_th" when linking)
- · Use the ""_r"" functions instead of the normal API-functions
+ · Use the ""_r"" functions instead of the normal API-functions
- · Do not use any at-style time specifications. Parsing of such time
+ · Do not use any at-style time specifications. Parsing of such time
specifications is terribly non-thread-safe.
- · Never use non *"_r" functions unless it is explicitly documented
+ · Never use non *"_r" functions unless it is explicitly documented
that the function is tread-safe.
- · Every thread SHOULD call "rrd_get_context()" before its first call
+ · Every thread SHOULD call "rrd_get_context()" before its first call
to any "librrd_th" function in order to set up thread specific
data. This is not strictly required, but it is the only way to test
if memory allocation can be done by this function. Otherwise the
program may die with a SIGSEGV in a low-memory situation.
- · Always call "rrd_error_clear()" before any call to the library.
+ · Always call "rrd_error_clear()" before any call to the library.
Otherwise the call might fail due to some earlier error.
- N\bNO\bOT\bTE\bES\bS F\bFO\bOR\bR R\bRR\bRD\bD C\bCO\bON\bNT\bTR\bRI\bIB\bBU\bUT\bTO\bOR\bRS\bS
-
+ N\bNO\bOT\bTE\bES\bS F\bFO\bOR\bR R\bRR\bRD\bD C\bCO\bON\bNT\bTR\bRI\bIB\bBU\bUT\bTO\bOR\bRS\bS
Some precautions must be followed when developing RRD from now on:
- · Only use thread-safe functions in library code. Many often used
- libc functions aren't thread-safe. Take care in the following situ-
- ations or when using the following library functions:
+ · Only use thread-safe functions in library code. Many often used
+ libc functions aren't thread-safe. Take care in the following
+ situations or when using the following library functions:
- · Direct calls to "strerror()" must be avoided: use "rrd_str-
- error()" instead, it provides a per-thread error message.
+ · Direct calls to "strerror()" must be avoided: use
+ "rrd_strerror()" instead, it provides a per-thread error
+ message.
- · The "getpw*", "getgr*", "gethost*" function families (and some
- more "get*" functions) are not thread-safe: use the *"_r" vari-
- ants
+ · The "getpw*", "getgr*", "gethost*" function families (and some
+ more "get*" functions) are not thread-safe: use the *"_r"
+ variants
- · Time functions: "asctime", "ctime", "gmtime", "localtime": use
+ · Time functions: "asctime", "ctime", "gmtime", "localtime": use
*"_r" variants
- · "strtok": use "strtok_r"
+ · "strtok": use "strtok_r"
- · "tmpnam": use "tmpnam_r"
+ · "tmpnam": use "tmpnam_r"
- · Many others (lookup documentation)
+ · Many others (lookup documentation)
- · A header file named _\br_\br_\bd_\b__\bi_\bs_\b__\bt_\bh_\br_\be_\ba_\bd_\b__\bs_\ba_\bf_\be_\b._\bh is provided that works
+ · A header file named _\br_\br_\bd_\b__\bi_\bs_\b__\bt_\bh_\br_\be_\ba_\bd_\b__\bs_\ba_\bf_\be_\b._\bh is provided that works
with the GNU C-preprocessor to "poison" some of the most common
non-thread-safe functions using the "#pragma GCC poison" directive.
- Just include this header in source files you want to keep
- thread-safe.
+ Just include this header in source files you want to keep thread-
+ safe.
- · Do not introduce global variables!
+ · Do not introduce global variables!
If you really, really have to use a global variable you may add a
new field to the "rrd_context" structure and modify _\br_\br_\bd_\b__\be_\br_\br_\bo_\br_\b._\bc,
_\br_\br_\bd_\b__\bt_\bh_\br_\be_\ba_\bd_\b__\bs_\ba_\bf_\be_\b._\bc and _\br_\br_\bd_\b__\bn_\bo_\bn_\b__\bt_\bh_\br_\be_\ba_\bd_\b__\bs_\ba_\bf_\be_\b._\bc
- · Do not use "getopt" or "getopt_long" in *"_r" (neither directly nor
+ · Do not use "getopt" or "getopt_long" in *"_r" (neither directly nor
indirectly).
"getopt" uses global variables and behaves badly in a multi-
provide argc and **argv arguments for variable length argument
lists. See "rrd_update_r" as an example.
- · Do not use the "rrd_parsetime" function!
+ · Do not use the "rrd_parsetime" function!
It uses lots of global variables. You may use it in functions not
designed to be thread-safe, like in functions wrapping the "_r"
- version of some operation (e.g., "rrd_create", but not in "rrd_cre-
- ate_r")
-
- C\bCU\bUR\bRR\bRE\bEN\bNT\bTL\bLY\bY I\bIM\bMP\bPL\bLE\bEM\bME\bEN\bNT\bTE\bED\bD T\bTH\bHR\bRE\bEA\bAD\bD S\bSA\bAF\bFE\bE F\bFU\bUN\bNC\bCT\bTI\bIO\bON\bNS\bS
+ version of some operation (e.g., "rrd_create", but not in
+ "rrd_create_r")
- Currently there exist thread-safe variants of "rrd_update", "rrd_cre-
- ate", "rrd_dump", "rrd_info", "rrd_last", and "rrd_fetch".
+ C\bCU\bUR\bRR\bRE\bEN\bNT\bTL\bLY\bY I\bIM\bMP\bPL\bLE\bEM\bME\bEN\bNT\bTE\bED\bD T\bTH\bHR\bRE\bEA\bAD\bD S\bSA\bAF\bFE\bE F\bFU\bUN\bNC\bCT\bTI\bIO\bON\bNS\bS
+ Currently there exist thread-safe variants of "rrd_update",
+ "rrd_create", "rrd_dump", "rrd_info", "rrd_last", and "rrd_fetch".
A\bAU\bUT\bTH\bHO\bOR\bR
Peter Stamfest <peter@stamfest.at>
-1.3.99909060808 2008-06-08 RRDTHREADS(1)
+1.3.999 2009-04-19 RRDTHREADS(1)