Commit 22f2e280 authored by Derek Fults's avatar Derek Fults Committed by Linus Torvalds

[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='
<cpu number>,...,<cpu number>
<cpu number>-<cpu number>  (must be a positive range in ascending
or a mixture
<cpu number>,...,<cpu number>-<cpu number>
Signed-off-by: default avatarDerek Fults <>
Cc: "Randy.Dunlap" <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 8f63fdbb
......@@ -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>
<cpu number>,...,<cpu number>
<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
......@@ -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;
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)
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)
if (res == 3) {
int range_nums;
range_nums = get_range((char **)&str, ints + i);
if (range_nums < 0)
* 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);
if (res == 1)
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