man-pages/man-pages-3.22-sched_setaffinity.patch

diff -up man-pages-3.22/man2/sched_setaffinity.2.orig man-pages-3.22/man2/sched_setaffinity.2
--- man-pages-3.22/man2/sched_setaffinity.2.orig	2009-07-25 08:53:26.000000000 +0200
+++ man-pages-3.22/man2/sched_setaffinity.2	2009-12-02 15:29:17.000000000 +0100
@@ -212,6 +212,60 @@ system call returns the size (in bytes) 
 .I cpumask_t
 data type that is used internally by the kernel to
 represent the CPU set bit mask.
+
+The \fBcpu_set_t\fR affinity mask size provided by glibc only allows for upto
+1024 CPUs. It is possible to build Linux kernels with greater than 1024
+CPUs. Any application using the statically sized \fBcpu_set_t\fR will fail
+with \fBEINVAL\fR on such kernels. It is thus recommended that applications
+avoid using the statically sized \fBcpu_set_t\fR type, and instead dynamically
+allocate a mask using the CPU_*_S macros described in the \fBCPU_SET(3)\fR man
+page. Since it is not possible to determine ahead of time what \fBNR_CPUS\fR
+value the kernel was built with, applications must be prepared to catch
+\fBEINVAL\fR, and retry the command with a larger dynamically allocated mask.
+The example that follows illustrates portable usage.
+
+.SH EXAMPLE
+.nf
+   #define _GNU_SOURCE
+
+   #include <sched.h>
+   #include <stdio.h>
+   #include <errno.h>
+
+   int main(void)
+   {
+        cpu_set_t *mask;
+        size_t size;
+        int i;
+        int nrcpus = 1024;
+
+realloc:
+        mask = CPU_ALLOC(nrcpus);
+        size = CPU_ALLOC_SIZE(nrcpus);
+        CPU_ZERO_S(size, mask);
+        if ( sched_getaffinity(0, size, mask) == -1 ) {
+                CPU_FREE(mask);
+                if (errno == EINVAL &&
+                    nrcpus < (1024 << 8)) {
+                       nrcpus = nrcpus << 2;
+                       goto realloc;
+                }
+                perror("sched_getaffinity");
+                return -1;
+        }
+
+        for ( i = 0; i < nrcpus; i++ ) {
+                if ( CPU_ISSET_S(i, size, mask) ) {
+                        printf("CPU %d is set\\n", (i+1));
+                }
+        }
+
+        CPU_FREE(mask);
+
+        return 0;
+   }
+.fi
+
 .SH "SEE ALSO"
 .BR clone (2),
 .BR getcpu (2),