Threads Library Functions pthread_create(3THR) NAME pthread_create - create a thread SYNOPSIS cc -mt [ _f_l_a_g... ] _f_i_l_e...- lpthread [ _l_i_b_r_a_r_y... ] #include int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine, void*),void *arg); DESCRIPTION The pthread_create() function is used to create a new thread, with attributes specified by _a_t_t_r, within a process. If _a_t_t_r is _N_U_L_L, the default attributes are used. (See pthread_attr_init(3THR)). If the attributes specified by _a_t_t_r are modified later, the thread's attributes are not affected. Upon successful completion, pthread_create() stores the ID of the created thread in the location refer- enced by _t_h_r_e_a_d. The thread is created executing _s_t_a_r_t__r_o_u_t_i_n_e with _a_r_g as its sole argument. If the _s_t_a_r_t__r_o_u_t_i_n_e returns, the effect is as if there was an implicit call to pthread_exit() using the return value of _s_t_a_r_t__r_o_u_t_i_n_e as the exit status. Note that the thread in which main() was originally invoked differs from this. When it returns from main(), the effect is as if there was an implicit call to exit() using the return value of main() as the exit status. The signal state of the new thread is initialised as fol- lows: +o The signal mask is inherited from the creating thread. +o The set of signals pending for the new thread is empty. Default thread creation: pthread_t tid; void *start_func(void *), *arg; pthread_create(&tid, NULL, start_func, arg); This would have the same effect as: pthread_attr_t attr; pthread_attr_init(&attr); /* initialize attr with default attributes */ pthread_create(&tid, &attr, start_func, arg); SunOS 5.8 Last change: 15 May 1998 1 Threads Library Functions pthread_create(3THR) User-defined thread creation: To create a thread that is scheduled on a system-wide basis, use: pthread_attr_init(&attr); /* initialize attr with default attributes */ pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM); /* system-wide contention */ pthread_create(&tid, &attr, start_func, arg); To customize the attributes for POSIX threads, see pthread_attr_init(3THR). A new thread created with pthread_create() uses the stack specified by the _s_t_a_c_k_a_d_d_r attribute, and the stack contin- ues for the number of bytes specified by the _s_t_a_c_k_s_i_z_e attribute. By default, the stack size is 1 megabyte for 32- bit processes and 2 megabyte for 64-bit processes (see pthread_attr_setstacksize(3THR)). If the default is used for both the _s_t_a_c_k_a_d_d_r and _s_t_a_c_k_s_i_z_e attributes, pthread_create() creates a stack for the new thread with at least 1 megabyte for 32-bit processes and 2 megabyte for 64-bit processes. (For customizing stack sizes, see NOTES). If pthread_create() fails, no new thread is created and the contents of the location referenced by _t_h_r_e_a_d are undefined. RETURN VALUES If successful, the pthread_create() function returns 0. Otherwise, an error number is returned to indicate the error. ERRORS The pthread_create() function will fail if: ENOMEM The system lacked the necessary resources to create another thread. EINVAL The value specified by _a_t_t_r is invalid. EPERM The caller does not have appropriate permission to set the required scheduling parameters or scheduling pol- icy. EXAMPLES Example 1: This is an example of concurrency with multi- threading. Since POSIX threads and Solaris threads are fully compatible even within the same process, this example uses pthread_create() if you execute a.out 0, or thr_create() if you execute a.out 1. Five threads are created that simultaneously perform a time-consuming function, sleep(10). If the execution of this SunOS 5.8 Last change: 15 May 1998 2 Threads Library Functions pthread_create(3THR) process is timed, the results will show that all five indi- vidual calls to sleep for ten-seconds completed in about ten seconds, even on a uniprocessor. If a single-threaded pro- cess calls sleep(10) five times, the execution time will be about 50-seconds. The command-line to time this process is: /usr/bin/time a.out 0 (for POSIX threading) or /usr/bin/time a.out 1 (for Solaris threading) /* cc thisfile.c -lthread -lpthread */ #define _REENTRANT /* basic 3-lines for threads */ #include #include #define NUM_THREADS 5 #define SLEEP_TIME 10 void *sleeping(void *); /* thread routine */ int i; thread_t tid[NUM_THREADS]; /* array of thread IDs */ int main(int argc, char *argv[]) { if (argc == 1) { printf("use 0 as arg1 to use pthread_create()\n"); printf("or use 1 as arg1 to use thr_create()\n"); return (1); } switch (*argv[1]) { case '0': /* POSIX */ for ( i = 0; i < NUM_THREADS; i++) pthread_create(&tid[i], NULL, sleeping, (void *)SLEEP_TIME); for ( i = 0; i < NUM_THREADS; i++) pthread_join(tid[i], NULL); break; case '1': /* Solaris */ for ( i = 0; i < NUM_THREADS; i++) thr_create(NULL, 0, sleeping, (void *)SLEEP_TIME, 0, &tid[i]); while (thr_join(NULL, NULL, NULL) == 0) ; break; } /* switch */ SunOS 5.8 Last change: 15 May 1998 3 Threads Library Functions pthread_create(3THR) printf("main() reporting that all %d threads have terminated\n", i); return (0); } /* main */ void * sleeping(void *arg) { int sleep_time = (int)arg; printf("thread %d sleeping %d seconds ...\n", thr_self(), sleep_time); sleep(sleep_time); printf("\nthread %d awakening\n", thr_self()); return (NULL); } Example 2: If main() had not waited for the completion of the other threads (using pthread_join(3THR) or thr_join(3THR)), it would have continued to process con- currently until it reached the end of its routine and the entire process would have exited prematurely (see exit(2)). ATTRIBUTES See attributes(5) for descriptions of the following attri- butes: ____________________________________________________________ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | |______________________________|______________________________| | MT-Level | MT-Safe | |______________________________|______________________________| SEE ALSO fork(2), sysconf(3C), pthread_attr_init(3THR), pthread_cancel(3THR), pthread_exit(3THR), pthread_join(3THR), attributes(5), standards(5) NOTES MT application threads execute independently of each other, thus their relative behavior is unpredictable. Therefore, it is possible for the thread executing main() to finish before all other user application threads. pthread_join(3THR), on the other hand, must specify the ter- minating thread (IDs) for which it will wait. A user-specified stack size must be greater than the value PTHREAD_STACK_MIN. A minimum stack size may not accommodate the stack frame for the user thread function _s_t_a_r_t__f_u_n_c. If a stack size is specified, it must accommodate _s_t_a_r_t__f_u_n_c requirements and the functions that it may call in turn, in addition to the minimum requirement. SunOS 5.8 Last change: 15 May 1998 4 Threads Library Functions pthread_create(3THR) It is usually very difficult to determine the runtime stack requirements for a thread. PTHREAD_STACK_MIN specifies how much stack storage is required to execute a _N_U_L_L _s_t_a_r_t__f_u_n_c. The total runtime requirements for stack storage are depen- dent on the storage required to do runtime linking, the amount of storage required by library runtimes (as printf()) that your thread calls. Since these storage parameters are not known before the program runs, it is best to use default stacks. If you know your runtime requirements or decide to use stacks that are larger than the default, then it makes sense to specify your own stacks. SunOS 5.8 Last change: 15 May 1998 5