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bitmap_parse: Support 'all' semantics

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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: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Yury Norov 2021-04-20 20:13:25 -07:00 committed by Paul E. McKenney
parent 6efb943b86
commit b18def121f
3 changed files with 21 additions and 0 deletions
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5
Documentation/admin-guide/kernel-parameters.rst
View file

@ -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

9
lib/bitmap.c
View file

@ -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;

7
lib/test_bitmap.c
View file

@ -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},