Here's another pthreads page looking for reviewers (and testers for the example program) thanks, Michael .\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk .\" <mtk.manpages@xxxxxxxxx> .\" .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" .TH PTHREAD_SETSCHEDPARAM 3 2008-11-07 "Linux" "Linux Programmer's Manual" .SH NAME pthread_setschedparam, pthread_setschedparam \- set/get scheduling policy and parameters of a thread .SH SYNOPSIS .nf .B #include <pthread.h> .BI "pthread_setschedparam(pthread_t " thread ", int " policy , .BI " const struct sched_param *" param ); .BI "pthread_getschedparam(pthread_t " thread ", int *" policy , .BI " struct sched_param *" param ); .sp Compile and link with \fI\-pthread\fP. .SH DESCRIPTION The .BR pthread_setschedparam () function sets the scheduling policy and parameters of the thread .IR thread . .I policy specifies the new scheduling policy for .IR thread . The supported values for .IR policy , and their semantics, are described in .BR sched_setscheduler (2). .\" FIXME . pthread_setschedparam() places no restriction on the policy, .\" but pthread_attr_setschedpolicy() restricts policy to RR/FIFO/OTHER .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7013 The structure pointed to by .I param specifies the new scheduling parameters for .IR thread . Scheduling parameters are maintained in the following structure: .in +4n .nf struct sched_param { int sched_priority; /* Scheduling priority */ }; .fi .in As can be seen, only one scheduling parameter is supported (this is the only parameter specified by POSIX.1-2001.) For details of the permitted ranges for scheduling priorities in each scheduling policy, see .BR sched_setscheduler (2). The .BR pthread_getschedparam () function returns the scheduling policy and parameters of the thread .IR thread , in the buffers pointed to by .I policy and .IR param , respectively. The returned priority value is that set by the most recent .BR pthread_setschedparam (), .BR pthread_setschedprio (3), or .BR pthread_create (3) call that affected .IR 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, .BR pthread_mutexattr_setprioceiling (3) and .BR pthread_mutexattr_setprotocol (3)). .\" FIXME . nptl/pthread_setschedparam.c has the following .\" /* If the thread should have higher priority because of some .\" PTHREAD_PRIO_PROTECT mutexes it holds, adjust the priority. */ .\" Eventually (perhaps after writing the mutexattr pages), we .\" may want to add something on the topic to this page. .SH RETURN VALUE On success, these functions return 0; on error, they return a non-zero error number. If .BR pthread_setschedparam () fails, the scheduling policy and parameters of .I thread are not changed. .SH ERRORS Both of these functions may fail with the following error: .TP .B ESRCH No thread with the ID .I thread could be found. .PP .BR pthread_setschedparam () may additionally fail with the following errors: .TP .B EINVAL .I policy is not a recognized policy, or .I param does not make sense for the .IR policy . .TP .B EPERM The caller does not have appropriate privileges .RB ( CAP_SYS_NICE ) to set the specified scheduling policy and parameters. See .BR sched_setscheduler (2) for more details on what scheduling changes require privileges. .PP POSIX.1-2001 also documents an .B ENOTSUP ("attempt was made to set the policy or scheduling parameters to an unsupported value") error for .BR pthread_setschedparam (). .\" .SH VERSIONS .\" Available since glibc 2.0 .SH CONFORMING TO POSIX.1-2001. .SH NOTES See .BR sched_setscheduler (2) for a description of the effect of changing a thread's scheduling policy and priority. .SH EXAMPLE The program below demonstrates the use of .BR pthread_setschedparam () and .BR pthread_getschedparam (), as well as the use of a number of other scheduling-related pthreads functions. In the following run, the main thread sets its scheduling policy to .BR SCHED_FIFO with a priority of 10, and initializes a thread attributes object with a scheduling policy attribute of .BR SCHED_RR and a scheduling priority attribute of 20. The program then sets (using .BR pthread_attr_setinheritsched (3)) the inherit scheduler attribute of the thread attributes object to .BR PTHREAD_EXPLICIT_SCHED , meaning that threads created using this attributes object should take their scheduling 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. .in +4n .nf $ \fBsu\fP # Need privilege to set real-time scheduling policies Password: # \fB./a.out \-mf10 \-ar20 \-i e\fP Scheduler settings of main thread policy=SCHED_FIFO, priority=10 Scheduler settings in \(aqattr\(aq policy=SCHED_RR, priority=20 inheritsched is EXPLICIT Scheduler attributes of new thread policy=SCHED_RR, priority=20 .fi .in In the above output, one can see that the scheduling policy and priority 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 .BR 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. .in +4n .nf # \fB./a.out \-mf10 \-ar20 \-i i\fP Scheduler settings of main thread policy=SCHED_FIFO, priority=10 Scheduler settings in \(aqattr\(aq policy=SCHED_RR, priority=20 inheritsched is INHERIT Scheduler attributes of new thread policy=SCHED_FIFO, priority=10 .fi .in In the above output, one can see that the scheduling policy and priority were taken from the creating thread, rather than the thread attributes object. .SS Program source \& .nf /* pthreads_sched_test.c */ #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> /* Simple error handling functions */ #define errExit(msg) { perror(msg); exit(EXIT_FAILURE); } #define errExitEN(en, msg) { errno = en; perror(msg); \\ exit(EXIT_FAILURE); } 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(" \(aqexplicit\(aq or \(aqinherit\(aq\\n"); fpe("\-m<policy><prio> Set scheduling policy and priority on\\n"); fpe(" main thread before pthread_create() call\\n"); exit(EXIT_FAILURE); } /* usage */ static int get_policy(char p, int *policy) { switch (p) { case \(aqf\(aq: *policy = SCHED_FIFO; return 1; case \(aqr\(aq: *policy = SCHED_RR; return 1; case \(aqo\(aq: *policy = SCHED_OTHER; return 1; default: return 0; } } /* get_policy */ 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); } /* display_sched_attr */ static void display_thread_sched_attr(char *msg) { int policy, s; struct sched_param param; s = pthread_getschedparam(pthread_self(), &policy, ¶m); if (s != 0) errExitEN(s, "pthread_getschedparam"); printf("%s\\n", msg); display_sched_attr(policy, ¶m); } /* display_thread_sched_attr */ static void * thread_start(void *arg) { display_thread_sched_attr("Scheduler attributes of new thread"); return NULL; } /* thread_start */ 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 \(aqa\(aq: attr_sched_str = optarg; break; case \(aqA\(aq: use_null_attrib = 1; break; case \(aqi\(aq: inheritsched_str = optarg; break; case \(aqm\(aq: 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\(aqt 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, ¶m); if (s != 0) errExitEN(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) errExitEN(s, "pthread_attr_init"); attrp = &attr; } if (inheritsched_str != NULL) { if (inheritsched_str[0] == \(aqe\(aq) inheritsched = PTHREAD_EXPLICIT_SCHED; else if (inheritsched_str[0] == \(aqi\(aq) inheritsched = PTHREAD_INHERIT_SCHED; else usage(argv[0], "Value for \-i must be \(aqe\(aq or \(aqi\(aq\\n"); s = pthread_attr_setinheritsched(&attr, inheritsched); if (s != 0) errExitEN(s, "pthread_attr_setinheritsched"); } if (attr_sched_str != NULL) { if (!get_policy(attr_sched_str[0], &policy)) usage(argv[0], "Bad policy for \(aqattr\(aq (\-a)\\n"); param.sched_priority = strtol(&attr_sched_str[1], NULL, 0); s = pthread_attr_setschedpolicy(&attr, policy); if (s != 0) errExitEN(s, "pthread_attr_setschedpolicy"); s = pthread_attr_setschedparam(&attr, ¶m); if (s != 0) errExitEN(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, ¶m); if (s != 0) errExitEN(s, "pthread_attr_getschedparam"); s = pthread_attr_getschedpolicy(&attr, &policy); if (s != 0) errExitEN(s, "pthread_attr_getschedpolicy"); printf("Scheduler settings in \(aqattr\(aq\\n"); display_sched_attr(policy, ¶m); 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) errExitEN(s, "pthread_create"); /* Destroy unneeded thread attributes object */ s = pthread_attr_destroy(&attr); if (s != 0) errExitEN(s, "pthread_attr_destroy"); s = pthread_join(thread, NULL); if (s != 0) errExitEN(s, "pthread_join"); exit(EXIT_SUCCESS); } /* main */ .fi .SH SEE ALSO .BR sched_get_priority_min (2), .BR sched_setscheduler (2), .BR pthread_attr_init (3), .BR pthread_attr_setinheritsched (3), .BR pthread_attr_setschedparam (3), .BR pthread_attr_setschedpolicy (3), .BR pthread_setschedprio (3), .BR pthread_create (3), .BR pthread_self (3), .BR pthreads (7) -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
