diff options
Diffstat (limited to 'man3/pthread_setschedparam.3')
| -rw-r--r-- | man3/pthread_setschedparam.3 | 448 |
1 files changed, 448 insertions, 0 deletions
diff --git a/man3/pthread_setschedparam.3 b/man3/pthread_setschedparam.3 new file mode 100644 index 0000000..62a5832 --- /dev/null +++ b/man3/pthread_setschedparam.3 @@ -0,0 +1,448 @@ +'\" t +.\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk +.\" <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.TH pthread_setschedparam 3 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +pthread_setschedparam, pthread_getschedparam \- set/get +scheduling policy and parameters of a thread +.SH LIBRARY +POSIX threads library +.RI ( libpthread ", " \-lpthread ) +.SH SYNOPSIS +.nf +.B #include <pthread.h> +.PP +.BI "int pthread_setschedparam(pthread_t " thread ", int " policy , +.BI " const struct sched_param *" param ); +.BI "int pthread_getschedparam(pthread_t " thread ", int *restrict " policy , +.BI " struct sched_param *restrict " param ); +.fi +.SH DESCRIPTION +The +.BR pthread_setschedparam () +function sets the scheduling policy and parameters of the thread +.IR thread . +.PP +.I policy +specifies the new scheduling policy for +.IR thread . +The supported values for +.IR policy , +and their semantics, are described in +.BR sched (7). +.\" 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 +.PP +The structure pointed to by +.I param +specifies the new scheduling parameters for +.IR thread . +Scheduling parameters are maintained in the following structure: +.PP +.in +4n +.EX +struct sched_param { + int sched_priority; /* Scheduling priority */ +}; +.EE +.in +.PP +As can be seen, only one scheduling parameter is supported. +For details of the permitted ranges for scheduling priorities +in each scheduling policy, see +.BR sched (7). +.PP +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 nonzero error number. +If +.BR pthread_setschedparam () +fails, the scheduling policy and parameters of +.I thread +are not changed. +.SH ERRORS +Both of these functions can 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 +to set the specified scheduling policy and parameters. +.PP +POSIX.1 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 ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR pthread_setschedparam (), +.BR pthread_getschedparam () +T} Thread safety MT-Safe +.TE +.sp 1 +.SH STANDARDS +POSIX.1-2008. +.SH HISTORY +glibc 2.0 +POSIX.1-2001. +.SH 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 +.BR sched (7). +.SH EXAMPLES +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. +.PP +In the following run, the main thread sets its scheduling policy to +.B SCHED_FIFO +with a priority of 10, +and initializes a thread attributes object with +a scheduling policy attribute of +.B 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. +.PP +.in +4n +.EX +$ \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 \[aq]attr\[aq] + policy=SCHED_RR, priority=20 + inheritsched is EXPLICIT +\& +Scheduler attributes of new thread + policy=SCHED_RR, priority=20 +.EE +.in +.PP +In the above output, one can see that the scheduling policy and priority +were taken from the values specified in the thread attributes object. +.PP +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. +.PP +.in +4n +.EX +# \fB./a.out \-mf10 \-ar20 \-i i\fP +Scheduler settings of main thread + policy=SCHED_FIFO, priority=10 +\& +Scheduler settings in \[aq]attr\[aq] + policy=SCHED_RR, priority=20 + inheritsched is INHERIT +\& +Scheduler attributes of new thread + policy=SCHED_FIFO, priority=10 +.EE +.in +.PP +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. +.PP +Note that if we had omitted the +.I \-i\~i +option, the output would have been the same, since +.B PTHREAD_INHERIT_SCHED +is the default for the inherit scheduler attribute. +.SS Program source +\& +.\" SRC BEGIN (pthreads_sched_test.c) +.EX +/* pthreads_sched_test.c */ +\& +#include <errno.h> +#include <pthread.h> +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +\& +#define handle_error_en(en, msg) \e + 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]\en", prog_name); + fprintf(stderr, "Options are:\en"); +#define fpe(msg) fprintf(stderr, "\et%s", msg) /* Shorter */ + fpe("\-a<policy><prio> Set scheduling policy and priority in\en"); + fpe(" thread attributes object\en"); + fpe(" <policy> can be\en"); + fpe(" f SCHED_FIFO\en"); + fpe(" r SCHED_RR\en"); + fpe(" o SCHED_OTHER\en"); + fpe("\-A Use default thread attributes object\en"); + fpe("\-i {e|i} Set inherit scheduler attribute to\en"); + fpe(" \[aq]explicit\[aq] or \[aq]inherit\[aq]\en"); + fpe("\-m<policy><prio> Set scheduling policy and priority on\en"); + fpe(" main thread before pthread_create() call\en"); + exit(EXIT_FAILURE); +} +\& +static int +get_policy(char p, int *policy) +{ + switch (p) { + case \[aq]f\[aq]: *policy = SCHED_FIFO; return 1; + case \[aq]r\[aq]: *policy = SCHED_RR; return 1; + case \[aq]o\[aq]: *policy = SCHED_OTHER; return 1; + default: return 0; + } +} +\& +static void +display_sched_attr(int policy, struct sched_param *param) +{ + printf(" policy=%s, priority=%d\en", + (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, ¶m); + if (s != 0) + handle_error_en(s, "pthread_getschedparam"); +\& + printf("%s\en", msg); + display_sched_attr(policy, ¶m); +} +\& +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 \[aq]a\[aq]: attr_sched_str = optarg; break; + case \[aq]A\[aq]: use_null_attrib = 1; break; + case \[aq]i\[aq]: inheritsched_str = optarg; break; + case \[aq]m\[aq]: main_sched_str = optarg; break; + default: usage(argv[0], "Unrecognized option\en"); + } + } +\& + if (use_null_attrib + && (inheritsched_str != NULL || attr_sched_str != NULL)) + { + usage(argv[0], "Can\[aq]t specify \-A with \-i or \-a\en"); + } +\& + /* 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 (\-m)\en"); + param.sched_priority = strtol(&main_sched_str[1], NULL, 0); +\& + s = pthread_setschedparam(pthread_self(), policy, ¶m); + if (s != 0) + handle_error_en(s, "pthread_setschedparam"); + } +\& + display_thread_sched_attr("Scheduler settings of main thread"); + printf("\en"); +\& + /* 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] == \[aq]e\[aq]) + inheritsched = PTHREAD_EXPLICIT_SCHED; + else if (inheritsched_str[0] == \[aq]i\[aq]) + inheritsched = PTHREAD_INHERIT_SCHED; + else + usage(argv[0], "Value for \-i must be \[aq]e\[aq] or \[aq]i\[aq]\en"); +\& + 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 \[aq]attr\[aq] (\-a)\en"); + 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, ¶m); + 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, ¶m); + 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 \[aq]attr\[aq]\en"); + display_sched_attr(policy, ¶m); +\& + pthread_attr_getinheritsched(&attr, &inheritsched); + printf(" inheritsched is %s\en", + (inheritsched == PTHREAD_INHERIT_SCHED) ? "INHERIT" : + (inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" : + "???"); + printf("\en"); + } +\& + /* 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. */ +\& + if (!use_null_attrib) { + 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); +} +.EE +.\" SRC END +.SH SEE ALSO +.ad l +.nh +.BR getrlimit (2), +.BR sched_get_priority_min (2), +.BR pthread_attr_init (3), +.BR pthread_attr_setinheritsched (3), +.BR pthread_attr_setschedparam (3), +.BR pthread_attr_setschedpolicy (3), +.BR pthread_create (3), +.BR pthread_self (3), +.BR pthread_setschedprio (3), +.BR pthreads (7), +.BR sched (7) |