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       CPU_COUNT_S,  CPU_AND_S,  CPU_OR_S,  CPU_XOR_S,  CPU_EQUAL_S - macros for manipulating CPU


       #define _GNU_SOURCE             /* See feature_test_macros(7) */
       #include <sched.h>

       void CPU_ZERO(cpu_set_t *set);

       void CPU_SET(int cpu, cpu_set_t *set);
       void CPU_CLR(int cpu, cpu_set_t *set);
       int  CPU_ISSET(int cpu, cpu_set_t *set);

       int  CPU_COUNT(cpu_set_t *set);

       void CPU_AND(cpu_set_t *destset,
                    cpu_set_t *srcset1, cpu_set_t *srcset2);
       void CPU_OR(cpu_set_t *destset,
                    cpu_set_t *srcset1, cpu_set_t *srcset2);
       void CPU_XOR(cpu_set_t *destset,
                    cpu_set_t *srcset1, cpu_set_t *srcset2);

       int  CPU_EQUAL(cpu_set_t *set1, cpu_set_t *set2);

       cpu_set_t *CPU_ALLOC(int num_cpus);
       void CPU_FREE(cpu_set_t *set);
       size_t CPU_ALLOC_SIZE(int num_cpus);

       void CPU_ZERO_S(size_t setsize, cpu_set_t *set);

       void CPU_SET_S(int cpu, size_t setsize, cpu_set_t *set);
       void CPU_CLR_S(int cpu, size_t setsize, cpu_set_t *set);
       int  CPU_ISSET_S(int cpu, size_t setsize, cpu_set_t *set);

       int  CPU_COUNT_S(size_t setsize, cpu_set_t *set);

       void CPU_AND_S(size_t setsize, cpu_set_t *destset,
                    cpu_set_t *srcset1, cpu_set_t *srcset2);
       void CPU_OR_S(size_t setsize, cpu_set_t *destset,
                    cpu_set_t *srcset1, cpu_set_t *srcset2);
       void CPU_XOR_S(size_t setsize, cpu_set_t *destset,
                    cpu_set_t *srcset1, cpu_set_t *srcset2);

       int  CPU_EQUAL_S(size_t setsize, cpu_set_t *set1, cpu_set_t *set2);


       The  cpu_set_t  data  structure  represents  a  set  of  CPUs.   CPU  sets  are  used   by
       sched_setaffinity(2) and similar interfaces.

       The  cpu_set_t data type is implemented as a bit mask.  However, the data structure should
       be treated as opaque: all manipulation of CPU sets should be done via the macros described
       in this page.

       The following macros are provided to operate on the CPU set set:

       CPU_ZERO()       Clears set, so that it contains no CPUs.

       CPU_SET()        Add CPU cpu to set.

       CPU_CLR()        Remove CPU cpu from set.

       CPU_ISSET()      Test to see if CPU cpu is a member of set.

       CPU_COUNT()      Return the number of CPUs in set.

       Where  a  cpu  argument  is specified, it should not produce side effects, since the above
       macros may evaluate the argument more than once.

       The first CPU on the system corresponds to a cpu value of 0, the next CPU corresponds to a
       cpu  value  of  1,  and  so on.  No assumptions should be made about particular CPUs being
       available, or the  set  of  CPUs  being  contiguous,  since  CPUs  can  be  taken  offline
       dynamically or be otherwise absent.  The constant CPU_SETSIZE (currently 1024) specifies a
       value one greater than the maximum CPU number that can be stored in cpu_set_t.

       The following macros perform logical operations on CPU sets:

       CPU_AND()        Store the intersection of the sets srcset1 and srcset2 in destset  (which
                        may be one of the source sets).

       CPU_OR()         Store  the union of the sets srcset1 and srcset2 in destset (which may be
                        one of the source sets).

       CPU_XOR()        Store the XOR of the sets srcset1 and srcset2 in destset  (which  may  be
                        one  of  the  source  sets).   The  XOR means the set of CPUs that are in
                        either srcset1 or srcset2, but not both.

       CPU_EQUAL()      Test whether two CPU set contain exactly the same CPUs.

   Dynamically sized CPU sets
       Because some applications may require the ability to dynamically size CPU sets  (e.g.,  to
       allocate  sets  larger  than  that  defined  by  the  standard cpu_set_t data type), glibc
       nowadays provides a set of macros to support this.

       The following macros are used to allocate and deallocate CPU sets:

       CPU_ALLOC()      Allocate a CPU  set  large  enough  to  hold  CPUs  in  the  range  0  to

       CPU_ALLOC_SIZE() Return the size in bytes of the CPU set that would be needed to hold CPUs
                        in the range 0 to num_cpus-1.  This macro provides the value that can  be
                        used for the setsize argument in the CPU_*_S() macros described below.

       CPU_FREE()       Free a CPU set previously allocated by CPU_ALLOC().

       The macros whose names end with "_S" are the analogs of the similarly named macros without
       the suffix.  These macros perform the same tasks as their  analogs,  but  operate  on  the
       dynamically allocated CPU set(s) whose size is setsize bytes.


       CPU_ISSET() and CPU_ISSET_S() return nonzero if cpu is in set; otherwise, it returns 0.

       CPU_COUNT() and CPU_COUNT_S() return the number of CPUs in set.

       CPU_EQUAL() and CPU_EQUAL_S() return nonzero if the two CPU sets are equal; otherwise they
       return 0.

       CPU_ALLOC() returns a pointer on  success,  or  NULL  on  failure.   (Errors  are  as  for

       CPU_ALLOC_SIZE()  returns the number of bytes required to store a CPU set of the specified

       The other functions do not return a value.


       The CPU_ZERO(), CPU_SET(), CPU_CLR(), and CPU_ISSET() macros were added in glibc 2.3.3.

       CPU_COUNT() first appeared in glibc 2.6.

       CPU_ZERO_S(),    CPU_SET_S(),   CPU_CLR_S(),   CPU_ISSET_S(),   CPU_AND_S(),   CPU_OR_S(),
       CPU_XOR_S(), and CPU_EQUAL_S() first appeared in glibc 2.7.


       These interfaces are Linux-specific.


       To duplicate a CPU set, use memcpy(3).

       Since CPU sets are bit masks allocated in units of long words, the actual number  of  CPUs
       in  a  dynamically  allocated  CPU  set  will  be  rounded  up  to  the  next  multiple of
       sizeof(unsigned long).  An application should consider the contents of these extra bits to
       be undefined.

       Notwithstanding  the similarity in the names, note that the constant CPU_SETSIZE indicates
       the number of CPUs in the cpu_set_t data type (thus, it is effectively a count of the bits
       in the bit mask), while the setsize argument of the CPU_*_S() macros is a size in bytes.

       The  data types for arguments and return values shown in the SYNOPSIS are hints what about
       is expected in each case.  However, since these interfaces are implemented as macros,  the
       compiler won't necessarily catch all type errors if you violate the suggestions.


       On  32-bit platforms with glibc 2.8 and earlier, CPU_ALLOC() allocates twice as much space
       as is required, and CPU_ALLOC_SIZE() returns a value twice as large as  it  should.   This
       bug  should  not  affect  the semantics of a program, but does result in wasted memory and
       less efficient operation of the macros that operate on  dynamically  allocated  CPU  sets.
       These bugs are fixed in glibc 2.9.


       The  following  program  demonstrates  the  use of some of the macros used for dynamically
       allocated CPU sets.

       #define _GNU_SOURCE
       #include <sched.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <stdio.h>
       #include <assert.h>

       main(int argc, char *argv[])
           cpu_set_t *cpusetp;
           size_t size;
           int num_cpus, cpu;

           if (argc < 2) {
               fprintf(stderr, "Usage: %s <num-cpus>\n", argv[0]);

           num_cpus = atoi(argv[1]);

           cpusetp = CPU_ALLOC(num_cpus);
           if (cpusetp == NULL) {

           size = CPU_ALLOC_SIZE(num_cpus);

           CPU_ZERO_S(size, cpusetp);
           for (cpu = 0; cpu < num_cpus; cpu += 2)
               CPU_SET_S(cpu, size, cpusetp);

           printf("CPU_COUNT() of set:    %d\n", CPU_COUNT_S(size, cpusetp));



       sched_setaffinity(2), pthread_attr_setaffinity_np(3), pthread_setaffinity_np(3), cpuset(7)


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