DragonFly On-Line Manual Pages

Search: Section:  

LWP_SETAFFINITY(2)       DragonFly System Calls Manual      LWP_SETAFFINITY(2)


NAME

     lwp_setaffinity, lwp_getaffinity -- set and get a LWP's CPU affinity mask


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <sys/lwp.h>

     int
     lwp_setaffinity(pid_t pid, lwpid_t tid, const cpumask_t *mask);

     int
     lwp_getaffinity(pid_t pid, lwpid_t tid, cpumask_t *mask);


DESCRIPTION

     The lwp_setaffinity() system call sets the CPU affinity mask of the LWP,
     which is identified by the pid and the tid, to the value specified by the
     mask.  If the pid is zero, then the pid of the calling process is used.
     If the tid is less than zero, then all LWPs of the process identified by
     the pid are affected.  If the LWP specified by the pid and the tid is the
     current LWP it will be migrated immediately, if necessary, otherwise it
     will be migrated by the scheduler later.

     A process created by fork(2), vfork(2), and rfork(2) inherits the calling
     LWP's CPU affinity mask.  Same applies to the LWPs created by
     lwp_create(2), and the threads created by pthread_create(3).

     lwp_getaffinity() writes the affinity mask of the LWP, which is
     identified by the pid and the tid, to the cpumask_t structure pointed to
     by mask.  If the pid is zero, then the pid of the calling process is
     used.  If the tid is less than zero, then the first LWP of specified
     process is used.


RETURN VALUES

     These system calls return -1 on error and 0 upon successful completion.


ERRORS

     The lwp_setaffinity() and lwp_getaffinity() system calls will fail if:

     [EFAULT]           The name parameter is outside the process's allocated
                        address space.

     [EINVAL]           The pid parameter is negative.

     [ESRCH]            The LWP identified by the pid and the tid does not
                        exist.

     [EPERM]            The mask does not contain a valid CPU.


SEE ALSO

     fork(2), lwp_create(2), rfork(2), sched_getaffinity(2),
     sched_setaffinity(2), vfork(2), pthread_create(3),
     pthread_getaffinity_np(3), pthread_setaffinity_np(3)


HISTORY

     The lwp_setaffinity() and lwp_getaffinity() functions first appeared in
     DragonFly 4.7.

DragonFly 4.7                  January 14, 2017                  DragonFly 4.7

Search: Section: