linux: Add comment on affinity set sizes to tst-skeleton-affinity.c

Change-Id: Ic6ec48f75f3a0576d3121befd04531382c92afb4

diff --git a/sysdeps/unix/sysv/linux/tst-skeleton-affinity.c b/sysdeps/unix/sysv/linux/tst-skeleton-affinity.c
index 32fb94cdde24e42c50a313aa81b269c5025f4bc8..9d1f27fea9b4be1da5511bc9450855f5694d5104 100644 (file)
--- a/sysdeps/unix/sysv/linux/tst-skeleton-affinity.c
+++ b/sysdeps/unix/sysv/linux/tst-skeleton-affinity.c
@@ -264,6 +264,11 @@ do_test (void)
 
   struct conf conf;
   setup_conf (&conf);
+  /* Note: The CPU set size in bits can be less than the CPU count
+     (and the maximum test CPU) because the userspace interface rounds
+     up the bit count, and the rounded-up buffer size is passed into
+     the kernel.  The kernel does not know that some of the buffer are
+     actually padding, and writes data there.  */
   printf ("info: Detected CPU set size (in bits): %d\n", conf.set_size);
   printf ("info: Maximum test CPU: %d\n", conf.last_cpu);
   if (conf.set_size < 0 || conf.last_cpu < 0)