taskset: implement stride argument

function                                             old     new   delta
taskset_main                                         925     986     +61

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/util-linux/taskset.c b/util-linux/taskset.c
index 157bf5e4c..df1bc0a4f 100644
--- a/util-linux/taskset.c
+++ b/util-linux/taskset.c
@@ -121,10 +121,8 @@ static unsigned long *get_aff(int pid, unsigned *sz)
  * Parse the CPU list and set the mask accordingly.
  *
  * The list element can be either a CPU index or a range of CPU indices.
- * Example: "1,3,5-7".
- *
- * note1: stride (e.g. 0-255:2) is not supported
- * note2: leading and trailing whitespace is not allowed
+ * Example: "1,3,5-7". Stride can be specified: "0-7:2" is "0,2,4,6".
+ * Note: leading and trailing whitespace is not allowed.
  *  util-linux 2.31 allows leading and sometimes trailing whitespace:
  *  ok:     taskset -c ' 1,  2'
  *  ok:     taskset -c ' 1 , 2'
@@ -137,21 +135,28 @@ static void parse_cpulist(ul *mask, unsigned max, char *s)
         char *aff = s;
         for (;;) {
                 unsigned bit, end;
+                unsigned stride = 1;
 
                 bit = end = bb_strtou(s, &s, 10);
                 if (*s == '-') {
                         s++;
                         end = bb_strtou(s, &s, 10);
+                        if (*s == ':') {
+                                s++;
+                                stride = bb_strtou(s, &s, 10);
+                        }
                 }
                 if ((*s != ',' && *s != '\0')
                  || bit > end
                  || end == UINT_MAX /* bb_strtou returns this on malformed / ERANGE numbers */
+                 || stride == 0
+                 || stride == UINT_MAX
                 ) {
                         bb_error_msg_and_die("bad affinity '%s'", aff);
                 }
                 while (bit <= end && bit < max) {
                         mask[bit / BITS_UL] |= (1UL << (bit & MASK_UL));
-                        bit++;
+                        bit += stride;
                 }
                 if (*s == '\0')
                         break;