[PATCH] get_options to allow a hypenated range for isolcpus

This allows a hyphenated range of positive numbers in the string passed
to command line helper function, get_options.

Currently the command line option "isolcpus=" takes as its argument a
list of cpus.

Format: <cpu number>,...,<cpu number>
Valid values of <cpu_number>  include all cpus, 0 to "number of CPUs in
system - 1". This can get extremely long when isolating the majority of
cpus on a large system.  The kernel isolcpus code would not need any
changing to use this feature.  To use it, the change would be in the
command line format for 'isolcpus='
Format:
<cpu number>,...,<cpu number>
or
<cpu number>-<cpu number>  (must be a positive range in ascending
order.)
or a mixture
<cpu number>,...,<cpu number>-<cpu number>

Signed-off-by: Derek Fults <dfults@sgi.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 40 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1e183bd33d71..8fe6b834ef27 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -714,7 +714,12 @@ and is between 256 and 4096 characters. It is defined in the file
                         Format: <RDP>,<reset>,<pci_scan>,<verbosity>
 
         isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
-                        Format: <cpu number>,...,<cpu number>
+                        Format:
+                        <cpu number>,...,<cpu number>
+                        or
+                        <cpu number>-<cpu number>  (must be a positive range in ascending order)
+                        or a mixture
+                        <cpu number>,...,<cpu number>-<cpu number>
                         This option can be used to specify one or more CPUs
                         to isolate from the general SMP balancing and scheduling
                         algorithms. The only way to move a process onto or off
diff --git a/lib/cmdline.c b/lib/cmdline.c
index 0331ed825ea7..8a5b5303bd4f 100644
--- a/lib/cmdline.c
+++ b/lib/cmdline.c
@@ -16,6 +16,23 @@
 #include <linux/kernel.h>
 #include <linux/string.h>
 
+/*
+ *      If a hyphen was found in get_option, this will handle the
+ *      range of numbers, M-N.  This will expand the range and insert
+ *      the values[M, M+1, ..., N] into the ints array in get_options.
+ */
+
+static int get_range(char **str, int *pint)
+{
+        int x, inc_counter, upper_range;
+
+        (*str)++;
+        upper_range = simple_strtol((*str), NULL, 0);
+        inc_counter = upper_range - *pint;
+        for (x = *pint; x < upper_range; x++)
+                *pint++ = x;
+        return inc_counter;
+}
 
 /**
  *      get_option - Parse integer from an option string
@@ -29,6 +46,7 @@
  *      0 : no int in string
  *      1 : int found, no subsequent comma
  *      2 : int found including a subsequent comma
+ *      3 : hyphen found to denote a range
  */
 
 int get_option (char **str, int *pint)
@@ -44,6 +62,8 @@ int get_option (char **str, int *pint)
                 (*str)++;
                 return 2;
         }
+        if (**str == '-')
+                return 3;
 
         return 1;
 }
@@ -55,7 +75,8 @@ int get_option (char **str, int *pint)
  *      @ints: integer array
  *
  *      This function parses a string containing a comma-separated
- *      list of integers.  The parse halts when the array is
+ *      list of integers, a hyphen-separated range of _positive_ integers,
+ *      or a combination of both.  The parse halts when the array is
  *      full, or when no more numbers can be retrieved from the
  *      string.
  *
@@ -72,6 +93,18 @@ char *get_options(const char *str, int nints, int *ints)
                 res = get_option ((char **)&str, ints + i);
                 if (res == 0)
                         break;
+                if (res == 3) {
+                        int range_nums;
+                        range_nums = get_range((char **)&str, ints + i);
+                        if (range_nums < 0)
+                                break;
+                        /*
+                         * Decrement the result by one to leave out the
+                         * last number in the range.  The next iteration
+                         * will handle the upper number in the range
+                         */
+                        i += (range_nums - 1);
+                }
                 i++;
                 if (res == 1)
                         break;