HP-UX Reference (11i v2 07/12) - 3 Library Functions N-Z (vol 7)

p
pthread(3T) pthread(3T)
(Pthread Library)
zyx = 21;
Each thread will have a different value associated with
zyx.
TLS variables can be statically initialized. Uninitialized TLS variables will be set to zero. Dynamically
loaded libraries (with
shl_load() ) can declare and use TLS variables.
TLS does have a cost in thread creation/termination operations, as TLS space for each thread must be allo-
cated and initialized, regardless of whether it will ever use the variables. This is true for modules linked
statically at startup. In case of dynamically loaded liabraries (with
sh_load()), TLS space for a thread
will be allocated when the TLS variables are accessed by it. If few threads actually use a large TLS area, it
may be wise to use the POSIX TSD instead (above).
REENTRANT LIBC & STDIO
Because they return pointers to library-internal static data, a number of libc functions cannot be used in
multithreaded programs. This is because calling these functions in a thread will overwrite the results of
previous calls in other threads. Alternate functions, having the suffix
_r (for reentrant), are provided
within libc for threaded programming.
Also, some primitives for synchronization of standard I/O operations are provided.
asctime_r() ,
ctime_r(),
getgrgid_t() ,
getgrnam_r() ,
getlogin_r() ,
getpwnam_r() ,
getpwuid_r() ,
gmtime_t() ,
localtime_r(),
rand_r(),
readdir_r() ,
strtok_r() ,
ttyname_r()
Provide reentrant versions of previously existing libc functions.
flockfile() ,
ftrylockfile(),
funlock()
Provide explicit synchronization for standard I/O streams.
MISCELLANEOUS FUNCTIONS
The section summarizes some miscellaneous pthread-related functions not covered in the preceding sec-
tions.
pthread_atfork() Establish special functions to be called just prior to and just subsequent to a
fork() operation.
pthread_equal() Tests whether two pthread_t values represent the same pthread.
pthread_once() Executes given function just once in a process, regardless of how many threads
make the same call. (Useful for one-time data initialization.)
pthread_self() Returns identifier (pthread_t) of calling thread.
THREAD DEBUGGING
Debugging of multithreaded programs is supported in the standard HP-UX debugger, dde. When any
thread is to be stopped due to a debugger event, the debugger will stop all threads. The register state,
stack, and data for any thread can be interrogated and manipulated.
See the dde(1) manpage and built-in graphical help system for more information.
TRACING FACILITIES
HP-UX provides a tracing facility for pthread operations. To use it, you must link your application using
the tracing version of the library:
178 Hewlett-Packard Company − 6 − HP-UX 11i Version 2: December 2007 Update