Commit b18def12 authored by Yury Norov's avatar Yury Norov Committed by Paul E. McKenney
Browse files

bitmap_parse: Support 'all' semantics 



RCU code supports an 'all' group as a special case when parsing rcu_nocbs
parameter. This patch moves the 'all' support to the core bitmap_parse
code, so that all bitmap users can enjoy this extension.

Moving 'all' parsing to a bitmap_parse level also allows users to pass
patterns together with 'all' in regular group:pattern format, for example,
"rcu_nocbs=all:1/2" would offload all the even-numbered CPUs regardless
of the number of CPUs on the system.

Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarYury Norov <yury.norov@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 6efb943b

Documentation/admin-guide/kernel-parameters.rst

+5 −0
Original line number Diff line number Diff line
@@ -76,6 +76,11 @@ to change, such as less cores in the CPU list, then N and any ranges using N 
will also change.  Use the same on a small 4 core system, and "16-N" becomes

"16-3" and now the same boot input will be flagged as invalid (start > end).



The special case-tolerant group name "all" has a meaning of selecting all CPUs,

so that "nohz_full=all" is the equivalent of "nohz_full=0-N".



The semantics of "N" and "all" is supported on a level of bitmaps and holds for

all users of bitmap_parse().



This document may not be entirely up to date and comprehensive. The command

"modinfo -p ${modulename}" shows a current list of all parameters of a loadable

lib/bitmap.c

+9 −0
Original line number Diff line number Diff line
@@ -581,6 +581,14 @@ static const char *bitmap_parse_region(const char *str, struct region *r) 
{

	unsigned int lastbit = r->nbits - 1;



	if (!strncasecmp(str, "all", 3)) {

		r->start = 0;

		r->end = lastbit;

		str += 3;



		goto check_pattern;

	}



	str = bitmap_getnum(str, &r->start, lastbit);

	if (IS_ERR(str))

		return str;
@@ -595,6 +603,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r) 
	if (IS_ERR(str))

		return str;



check_pattern:

	if (end_of_region(*str))

		goto no_pattern;

lib/test_bitmap.c

+7 −0
Original line number Diff line number Diff line
@@ -366,6 +366,13 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = { 
	{0, "0-31:1/3,1-31:1/3,2-31:1/3",	&exp1[8 * step], 32, 0},

	{0, "1-10:8/12,8-31:24/29,0-31:0/3",	&exp1[9 * step], 32, 0},



	{0,	  "all",		&exp1[8 * step], 32, 0},

	{0,	  "0, 1, all,  ",	&exp1[8 * step], 32, 0},

	{0,	  "all:1/2",		&exp1[4 * step], 32, 0},

	{0,	  "ALL:1/2",		&exp1[4 * step], 32, 0},

	{-EINVAL, "al", NULL, 8, 0},

	{-EINVAL, "alll", NULL, 8, 0},



	{-EINVAL, "-1",	NULL, 8, 0},

	{-EINVAL, "-0",	NULL, 8, 0},

	{-EINVAL, "10-1", NULL, 8, 0},