From: Jonathan Lim <jolim@redhat.com>
Date: Thu, 11 Oct 2007 15:19:21 -0400
Subject: [misc] Allow a hyphenated range for isolcpus
Message-id: 20071011191921.GE5008@sgi-desktop.boston.redhat.com
O-Subject: [RHEL5.2 PATCH] BZ 328151: Allow a hyphenated range for isolcpus
Bugzilla: 328151

Currently, the command line option "isolcpus=" takes as its argument a list of
cpus.  This can get extremely long when isolating the majority of cpus on a
large system.  This patch allows a hyphenated range of positive numbers in the
string passed to command line helper function, get_options.  The kernel
isolcpus code would not need any changing to use this feature.

The patch has been tested on x86_64 and is upstream:

  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=22f2e280179946b8be1e2205b8654f2cb4abbf64

Following is the diff against the 2.6.18-52.el5 kernel source:

Acked-by: Prarit Bhargava <prarit@redhat.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1e20a69..4f239be 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -727,7 +727,12 @@ running once the system is up.
 			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 0331ed8..8a5b530 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;