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PTHREAD_SETSCHEDPARAM(3)   Linux Programmer's Manual  PTHREAD_SETSCHEDPARAM(3)

NAME
       pthread_setschedparam,  pthread_getschedparam - set/get scheduling pol-
       icy and parameters of a thread

SYNOPSIS
       #include <pthread.h>

       int pthread_setschedparam(pthread_t thread, int policy,
                                 const struct sched_param *param);
       int pthread_getschedparam(pthread_t thread, int *policy,
                                 struct sched_param *param);

       Compile and link with -pthread.

DESCRIPTION
       The pthread_setschedparam() function sets  the  scheduling  policy  and
       parameters of the thread thread.

       policy  specifies  the new scheduling policy for thread.  The supported
       values for policy, and their semantics, are described in sched(7).

       The structure pointed to by param specifies the new scheduling  parame-
       ters for thread.  Scheduling parameters are maintained in the following
       structure:

           struct sched_param {
               int sched_priority;     /* Scheduling priority */
           };

       As can be seen,  only  one  scheduling  parameter  is  supported.   For
       details  of  the  permitted  ranges  for  scheduling priorities in each
       scheduling policy, see sched(7).

       The pthread_getschedparam() function returns the scheduling policy  and
       parameters  of  the  thread thread, in the buffers pointed to by policy
       and param, respectively.  The returned priority value is  that  set  by
       the  most  recent  pthread_setschedparam(), pthread_setschedprio(3), or
       pthread_create(3) call that affected  thread.   The  returned  priority
       does  not  reflect  any  temporary  priority adjustments as a result of
       calls to any priority inheritance or priority ceiling  functions  (see,
       for  example,  pthread_mutexattr_setprioceiling(3)  and  pthread_mutex-
       attr_setprotocol(3)).

RETURN VALUE
       On success, these functions return 0; on error, they return  a  nonzero
       error  number.  If pthread_setschedparam() fails, the scheduling policy
       and parameters of thread are not changed.

ERRORS
       Both of these functions can fail with the following error:

       ESRCH  No thread with the ID thread could be found.

       pthread_setschedparam()  may  additionally  fail  with  the   following
       errors:

       EINVAL policy  is not a recognized policy, or param does not make sense
              for the policy.

       EPERM  The caller does not have appropriate privileges to set the spec-
              ified scheduling policy and parameters.

       POSIX.1-2001  also  documents  an ENOTSUP ("attempt was made to set the
       policy or scheduling parameters to an  unsupported  value")  error  for
       pthread_setschedparam().

ATTRIBUTES
   Multithreading (see pthreads(7))
       The  pthread_setschedparam()  and pthread_getschedparam() functions are
       thread-safe.

CONFORMING TO
       POSIX.1-2001.

NOTES
       For a description of the permissions required to, and  the  effect  of,
       changing  a thread's scheduling policy and priority, and details of the
       permitted  ranges  for  priorities  in  each  scheduling  policy,   see
       sched(7).

EXAMPLE
       The  program  below demonstrates the use of pthread_setschedparam() and
       pthread_getschedparam(), as well as the use of a number of other sched-
       uling-related pthreads functions.

       In  the  following  run,  the main thread sets its scheduling policy to
       SCHED_FIFO with a priority of 10, and initializes a  thread  attributes
       object  with a scheduling policy attribute of SCHED_RR and a scheduling
       priority   attribute   of   20.    The   program   then   sets   (using
       pthread_attr_setinheritsched(3)) the inherit scheduler attribute of the
       thread  attributes  object  to  PTHREAD_EXPLICIT_SCHED,  meaning   that
       threads created using this attributes object should take their schedul-
       ing attributes from the thread attributes  object.   The  program  then
       creates  a  thread  using the thread attributes object, and that thread
       displays its scheduling policy and priority.

           $ su      # Need privilege to set real-time scheduling policies
           Password:
           # ./a.out -mf10 -ar20 -i e
           Scheduler settings of main thread
               policy=SCHED_FIFO, priority=10

           Scheduler settings in 'attr'
               policy=SCHED_RR, priority=20
               inheritsched is EXPLICIT

           Scheduler attributes of new thread
               policy=SCHED_RR, priority=20

       In the above output, one can see that the scheduling policy and  prior-
       ity  were  taken  from  the  values  specified in the thread attributes
       object.

       The next run is the same as  the  previous,  except  that  the  inherit
       scheduler  attribute  is  set  to  PTHREAD_INHERIT_SCHED,  meaning that
       threads created using the thread attributes object  should  ignore  the
       scheduling  attributes  specified  in the attributes object and instead
       take their scheduling attributes from the creating thread.

           # ./a.out -mf10 -ar20 -i i
           Scheduler settings of main thread
               policy=SCHED_FIFO, priority=10

           Scheduler settings in 'attr'
               policy=SCHED_RR, priority=20
               inheritsched is INHERIT

           Scheduler attributes of new thread
               policy=SCHED_FIFO, priority=10

       In the above output, one can see that the scheduling policy and  prior-
       ity  were  taken  from  the  creating  thread,  rather  than the thread
       attributes object.

       Note that if we had omitted the -i i option, the output would have been
       the  same,  since  PTHREAD_INHERIT_SCHED is the default for the inherit
       scheduler attribute.

   Program source

       /* pthreads_sched_test.c */

       #include <pthread.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <errno.h>

       #define handle_error_en(en, msg) \
               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

       static void
       usage(char *prog_name, char *msg)
       {
           if (msg != NULL)
               fputs(msg, stderr);

           fprintf(stderr, "Usage: %s [options]\n", prog_name);
           fprintf(stderr, "Options are:\n");
       #define fpe(msg) fprintf(stderr, "\t%s", msg);          /* Shorter */
           fpe("-a<policy><prio> Set scheduling policy and priority in\n");
           fpe("                 thread attributes object\n");
           fpe("                 <policy> can be\n");
           fpe("                     f  SCHED_FIFO\n");
           fpe("                     r  SCHED_RR\n");
           fpe("                     o  SCHED_OTHER\n");
           fpe("-A               Use default thread attributes object\n");
           fpe("-i {e|s}         Set inherit scheduler attribute to\n");
           fpe("                 'explicit' or 'inherit'\n");
           fpe("-m<policy><prio> Set scheduling policy and priority on\n");
           fpe("                 main thread before pthread_create() call\n");
           exit(EXIT_FAILURE);
       }

       static int
       get_policy(char p, int *policy)
       {
           switch (p) {
           case 'f': *policy = SCHED_FIFO;     return 1;
           case 'r': *policy = SCHED_RR;       return 1;
           case 'o': *policy = SCHED_OTHER;    return 1;
           default:  return 0;
           }
       }

       static void
       display_sched_attr(int policy, struct sched_param *param)
       {
           printf("    policy=%s, priority=%d\n",
                   (policy == SCHED_FIFO)  ? "SCHED_FIFO" :
                   (policy == SCHED_RR)    ? "SCHED_RR" :
                   (policy == SCHED_OTHER) ? "SCHED_OTHER" :
                   "???",
                   param->sched_priority);
       }

       static void
       display_thread_sched_attr(char *msg)
       {
           int policy, s;
           struct sched_param param;

           s = pthread_getschedparam(pthread_self(), &policy, &param);
           if (s != 0)
               handle_error_en(s, "pthread_getschedparam");

           printf("%s\n", msg);
           display_sched_attr(policy, &param);
       }

       static void *
       thread_start(void *arg)
       {
           display_thread_sched_attr("Scheduler attributes of new thread");

           return NULL;
       }

       int
       main(int argc, char *argv[])
       {
           int s, opt, inheritsched, use_null_attrib, policy;
           pthread_t thread;
           pthread_attr_t attr;
           pthread_attr_t *attrp;
           char *attr_sched_str, *main_sched_str, *inheritsched_str;
           struct sched_param param;

           /* Process command-line options */

           use_null_attrib = 0;
           attr_sched_str = NULL;
           main_sched_str = NULL;
           inheritsched_str = NULL;

           while ((opt = getopt(argc, argv, "a:Ai:m:")) != -1) {
               switch (opt) {
               case 'a': attr_sched_str = optarg;      break;
               case 'A': use_null_attrib = 1;          break;
               case 'i': inheritsched_str = optarg;    break;
               case 'm': main_sched_str = optarg;      break;
               default:  usage(argv[0], "Unrecognized option\n");
               }
           }

           if (use_null_attrib &&
                   (inheritsched_str != NULL || attr_sched_str != NULL))
               usage(argv[0], "Can't specify -A with -i or -a\n");

           /* Optionally set scheduling attributes of main thread,
              and display the attributes */

           if (main_sched_str != NULL) {
               if (!get_policy(main_sched_str[0], &policy))
                   usage(argv[0], "Bad policy for main thread (-s)\n");
               param.sched_priority = strtol(&main_sched_str[1], NULL, 0);

               s = pthread_setschedparam(pthread_self(), policy, &param);
               if (s != 0)
                   handle_error_en(s, "pthread_setschedparam");
           }

           display_thread_sched_attr("Scheduler settings of main thread");
           printf("\n");

           /* Initialize thread attributes object according to options */

           attrp = NULL;

           if (!use_null_attrib) {
               s = pthread_attr_init(&attr);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_init");
               attrp = &attr;
           }

           if (inheritsched_str != NULL) {
               if (inheritsched_str[0] == 'e')
                   inheritsched = PTHREAD_EXPLICIT_SCHED;
               else if (inheritsched_str[0] == 'i')
                   inheritsched = PTHREAD_INHERIT_SCHED;
               else
                   usage(argv[0], "Value for -i must be 'e' or 'i'\n");

               s = pthread_attr_setinheritsched(&attr, inheritsched);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_setinheritsched");
           }

           if (attr_sched_str != NULL) {
               if (!get_policy(attr_sched_str[0], &policy))
                   usage(argv[0],
                           "Bad policy for 'attr' (-a)\n");
               param.sched_priority = strtol(&attr_sched_str[1], NULL, 0);

               s = pthread_attr_setschedpolicy(&attr, policy);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_setschedpolicy");
               s = pthread_attr_setschedparam(&attr, &param);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_setschedparam");
           }

           /* If we initialized a thread attributes object, display
              the scheduling attributes that were set in the object */

           if (attrp != NULL) {
               s = pthread_attr_getschedparam(&attr, &param);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_getschedparam");
               s = pthread_attr_getschedpolicy(&attr, &policy);
               if (s != 0)
                   handle_error_en(s, "pthread_attr_getschedpolicy");

               printf("Scheduler settings in 'attr'\n");
               display_sched_attr(policy, &param);

               s = pthread_attr_getinheritsched(&attr, &inheritsched);
               printf("    inheritsched is %s\n",
                       (inheritsched == PTHREAD_INHERIT_SCHED)  ? "INHERIT" :
                       (inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" :
                       "???");
               printf("\n");
           }

           /* Create a thread that will display its scheduling attributes */

           s = pthread_create(&thread, attrp, &thread_start, NULL);
           if (s != 0)
               handle_error_en(s, "pthread_create");

           /* Destroy unneeded thread attributes object */

           s = pthread_attr_destroy(&attr);
           if (s != 0)
               handle_error_en(s, "pthread_attr_destroy");

           s = pthread_join(thread, NULL);
           if (s != 0)
               handle_error_en(s, "pthread_join");

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       getrlimit(2), sched_get_priority_min(2), pthread_attr_init(3),
       pthread_attr_setinheritsched(3), pthread_attr_setschedparam(3),
       pthread_attr_setschedpolicy(3), pthread_create(3), pthread_self(3),
       pthread_setschedprio(3), pthreads(7), sched(7)

COLOPHON
       This page is part of release 3.74 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       http://www.kernel.org/doc/man-pages/.

Linux                             2014-05-28          PTHREAD_SETSCHEDPARAM(3)

Czas wygenerowania: 0.01311 sek.


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