[PATCH tip/core/rcu 0/9] Add bitmap (thus CPU) ranges

[PATCH tip/core/rcu 0/9] Add bitmap (thus CPU) ranges

[Paul E. McKenney]

Hello!

This series adds ranges to bitmaps, and thus to CPU numbers, so that a
kernel boot parameter such as "rcu_nocbs=2-N" is now permitted.

1.	test_bitmap: clearly separate ERANGE from EINVAL tests, courtesy
	of Paul Gortmaker.

2.	test_bitmap: add tests to trigger ERANGE case, courtesy of
	Paul Gortmaker.

3.	test_bitmap: add more start-end:offset/len tests, courtesy of
	Paul Gortmaker.

4.	bitmap: fold nbits into region struct, courtesy of Paul Gortmaker.

5.	bitmap: move ERANGE check from set_region to check_region,
	courtesy of Paul Gortmaker.

6.	bitmap: support "N" as an alias for size of bitmap, courtesy of
	Paul Gortmaker.

7.	test_bitmap: add tests for "N" alias, courtesy of Paul Gortmaker.

8.	deprecate "all" option to rcu_nocbs=, courtesy of Paul Gortmaker.

9.	Use "all" and "N" in "nohz_full" and "rcu_nocbs".

						Thanx, Paul

------------------------------------------------------------------------

 Documentation/admin-guide/kernel-parameters.rst            |    7 +
 Documentation/admin-guide/kernel-parameters.txt            |    4 
 kernel/rcu/tree_plugin.h                                   |    6 -
 lib/bitmap.c                                               |   55 +++++++------
 lib/test_bitmap.c                                          |   46 +++++++++-
 tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot |    2 
 tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot |    2 
 7 files changed, 84 insertions(+), 38 deletions(-)

[PATCH lib/bitmap 1/9] lib: test_bitmap: clearly separate ERANGE from EINVAL tests.

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

This block of tests was meant to find/flag incorrect use of the ":"
and "/" separators (syntax errors) and invalid (zero) group len.

However they were specified with an 8 bit width and 32 bit operations,
so they really contained two errors (EINVAL and ERANGE).

Promote them to 32 bit so it is clear what they are meant to target.
Then we can add tests specific for ERANGE (no syntax errors, just
doing 32bit op on 8 bit width, plus a typical 9-on-8 fencepost error).

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/test_bitmap.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 0ea0e82..853a3a6 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -337,12 +337,12 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{-EINVAL, "-1",	NULL, 8, 0},
 	{-EINVAL, "-0",	NULL, 8, 0},
 	{-EINVAL, "10-1", NULL, 8, 0},
-	{-EINVAL, "0-31:", NULL, 8, 0},
-	{-EINVAL, "0-31:0", NULL, 8, 0},
-	{-EINVAL, "0-31:0/", NULL, 8, 0},
-	{-EINVAL, "0-31:0/0", NULL, 8, 0},
-	{-EINVAL, "0-31:1/0", NULL, 8, 0},
-	{-EINVAL, "0-31:10/1", NULL, 8, 0},
+	{-EINVAL, "0-31:", NULL, 32, 0},
+	{-EINVAL, "0-31:0", NULL, 32, 0},
+	{-EINVAL, "0-31:0/", NULL, 32, 0},
+	{-EINVAL, "0-31:0/0", NULL, 32, 0},
+	{-EINVAL, "0-31:1/0", NULL, 32, 0},
+	{-EINVAL, "0-31:10/1", NULL, 32, 0},
 	{-EOVERFLOW, "0-98765432123456789:10/1", NULL, 8, 0},
 
 	{-EINVAL, "a-31", NULL, 8, 0},
-- 
2.9.5

[PATCH lib/bitmap 2/9] lib: test_bitmap: add tests to trigger ERANGE case.

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

Add tests that specify a valid range, but one that is outside the
width of the bitmap for which it is to be applied to.  These should
trigger an -ERANGE response from the code.

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/test_bitmap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 853a3a6..0f2e91d 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -337,6 +337,8 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{-EINVAL, "-1",	NULL, 8, 0},
 	{-EINVAL, "-0",	NULL, 8, 0},
 	{-EINVAL, "10-1", NULL, 8, 0},
+	{-ERANGE, "8-8", NULL, 8, 0},
+	{-ERANGE, "0-31", NULL, 8, 0},
 	{-EINVAL, "0-31:", NULL, 32, 0},
 	{-EINVAL, "0-31:0", NULL, 32, 0},
 	{-EINVAL, "0-31:0/", NULL, 32, 0},
-- 
2.9.5

[PATCH lib/bitmap 3/9] lib: test_bitmap: add more start-end:offset/len tests

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

There are inputs to bitmap_parselist() that would probably never
be entered manually by a person, but might result from some kind of
automated input generator.  Things like ranges of length 1, or group
lengths longer than nbits, overlaps, or offsets of zero.

Adding these tests serve two purposes:

1) document what might seem odd but nonetheless valid input.

2) don't regress from what we currently accept as valid.

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/test_bitmap.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 0f2e91d..3c1c46d 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -34,6 +34,8 @@ static const unsigned long exp1[] __initconst = {
 	BITMAP_FROM_U64(0x3333333311111111ULL),
 	BITMAP_FROM_U64(0xffffffff77777777ULL),
 	BITMAP_FROM_U64(0),
+	BITMAP_FROM_U64(0x00008000),
+	BITMAP_FROM_U64(0x80000000),
 };
 
 static const unsigned long exp2[] __initconst = {
@@ -334,6 +336,26 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{0, " ,  ,,  , ,   ",		&exp1[12 * step], 8, 0},
 	{0, " ,  ,,  , ,   \n",		&exp1[12 * step], 8, 0},
 
+	{0, "0-0",			&exp1[0], 32, 0},
+	{0, "1-1",			&exp1[1 * step], 32, 0},
+	{0, "15-15",			&exp1[13 * step], 32, 0},
+	{0, "31-31",			&exp1[14 * step], 32, 0},
+
+	{0, "0-0:0/1",			&exp1[12 * step], 32, 0},
+	{0, "0-0:1/1",			&exp1[0], 32, 0},
+	{0, "0-0:1/31",			&exp1[0], 32, 0},
+	{0, "0-0:31/31",		&exp1[0], 32, 0},
+	{0, "1-1:1/1",			&exp1[1 * step], 32, 0},
+	{0, "0-15:16/31",		&exp1[2 * step], 32, 0},
+	{0, "15-15:1/2",		&exp1[13 * step], 32, 0},
+	{0, "15-15:31/31",		&exp1[13 * step], 32, 0},
+	{0, "15-31:1/31",		&exp1[13 * step], 32, 0},
+	{0, "16-31:16/31",		&exp1[3 * step], 32, 0},
+	{0, "31-31:31/31",		&exp1[14 * step], 32, 0},
+
+	{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},
+
 	{-EINVAL, "-1",	NULL, 8, 0},
 	{-EINVAL, "-0",	NULL, 8, 0},
 	{-EINVAL, "10-1", NULL, 8, 0},
-- 
2.9.5

[PATCH lib/bitmap 4/9] lib: bitmap: fold nbits into region struct

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

This will reduce parameter passing and enable using nbits as part
of future dynamic region parameter parsing.

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Suggested-by: Yury Norov <yury.norov@gmail.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/bitmap.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 75006c4..162e285 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -487,24 +487,24 @@ EXPORT_SYMBOL(bitmap_print_to_pagebuf);
 
 /*
  * Region 9-38:4/10 describes the following bitmap structure:
- * 0	   9  12    18			38
- * .........****......****......****......
- *	    ^  ^     ^			 ^
- *      start  off   group_len	       end
+ * 0	   9  12    18			38	     N
+ * .........****......****......****..................
+ *	    ^  ^     ^			 ^	     ^
+ *      start  off   group_len	       end	 nbits
  */
 struct region {
 	unsigned int start;
 	unsigned int off;
 	unsigned int group_len;
 	unsigned int end;
+	unsigned int nbits;
 };
 
-static int bitmap_set_region(const struct region *r,
-				unsigned long *bitmap, int nbits)
+static int bitmap_set_region(const struct region *r, unsigned long *bitmap)
 {
 	unsigned int start;
 
-	if (r->end >= nbits)
+	if (r->end >= r->nbits)
 		return -ERANGE;
 
 	for (start = r->start; start <= r->end; start += r->group_len)
@@ -640,7 +640,8 @@ int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)
 	struct region r;
 	long ret;
 
-	bitmap_zero(maskp, nmaskbits);
+	r.nbits = nmaskbits;
+	bitmap_zero(maskp, r.nbits);
 
 	while (buf) {
 		buf = bitmap_find_region(buf);
@@ -655,7 +656,7 @@ int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)
 		if (ret)
 			return ret;
 
-		ret = bitmap_set_region(&r, maskp, nmaskbits);
+		ret = bitmap_set_region(&r, maskp);
 		if (ret)
 			return ret;
 	}
-- 
2.9.5

[PATCH lib/bitmap 5/9] lib: bitmap: move ERANGE check from set_region to check_region

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

It makes sense to do all the checks in check_region() and not 1/2
in check_region and 1/2 in set_region.

Since set_region is called immediately after check_region, the net
effect on runtime is zero, but it gets rid of an if (...) return...

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/bitmap.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 162e285..833f152a 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -500,17 +500,12 @@ struct region {
 	unsigned int nbits;
 };
 
-static int bitmap_set_region(const struct region *r, unsigned long *bitmap)
+static void bitmap_set_region(const struct region *r, unsigned long *bitmap)
 {
 	unsigned int start;
 
-	if (r->end >= r->nbits)
-		return -ERANGE;
-
 	for (start = r->start; start <= r->end; start += r->group_len)
 		bitmap_set(bitmap, start, min(r->end - start + 1, r->off));
-
-	return 0;
 }
 
 static int bitmap_check_region(const struct region *r)
@@ -518,6 +513,9 @@ static int bitmap_check_region(const struct region *r)
 	if (r->start > r->end || r->group_len == 0 || r->off > r->group_len)
 		return -EINVAL;
 
+	if (r->end >= r->nbits)
+		return -ERANGE;
+
 	return 0;
 }
 
@@ -656,9 +654,7 @@ int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)
 		if (ret)
 			return ret;
 
-		ret = bitmap_set_region(&r, maskp);
-		if (ret)
-			return ret;
+		bitmap_set_region(&r, maskp);
 	}
 
 	return 0;
-- 
2.9.5

[PATCH lib/bitmap 6/9] lib: bitmap: support "N" as an alias for size of bitmap

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

While this is done for all bitmaps, the original use case in mind was
for CPU masks and cpulist_parse() as described below.

It seems that a common configuration is to use the 1st couple cores for
housekeeping tasks.  This tends to leave the remaining ones to form a
pool of similarly configured cores to take on the real workload of
interest to the user.

So on machine A - with 32 cores, it could be 0-3 for "system" and then
4-31 being used in boot args like nohz_full=, or rcu_nocbs= as part of
setting up the worker pool of CPUs.

But then newer machine B is added, and it has 48 cores, and so while
the 0-3 part remains unchanged, the pool setup cpu list becomes 4-47.

Multiple deployment becomes easier when we can just simply replace 31
and 47 with "N" and let the system substitute in the actual number at
boot; a number that it knows better than we do.

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Suggested-by: Yury Norov <yury.norov@gmail.com> # move it from CPU code
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.rst |  7 +++++++
 lib/bitmap.c                                    | 22 +++++++++++++++++-----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index 1132796..d6e3f67 100644
--- a/Documentation/admin-guide/kernel-parameters.rst
+++ b/Documentation/admin-guide/kernel-parameters.rst
@@ -68,6 +68,13 @@ For example one can add to the command line following parameter:
 
 where the final item represents CPUs 100,101,125,126,150,151,...
 
+The value "N" can be used to represent the numerically last CPU on the system,
+i.e "foo_cpus=16-N" would be equivalent to "16-31" on a 32 core system.
+
+Keep in mind that "N" is dynamic, so if system changes cause the bitmap width
+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).
 
 
 This document may not be entirely up to date and comprehensive. The command
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 833f152a..9f4626a 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -519,11 +519,17 @@ static int bitmap_check_region(const struct region *r)
 	return 0;
 }
 
-static const char *bitmap_getnum(const char *str, unsigned int *num)
+static const char *bitmap_getnum(const char *str, unsigned int *num,
+				 unsigned int lastbit)
 {
 	unsigned long long n;
 	unsigned int len;
 
+	if (str[0] == 'N') {
+		*num = lastbit;
+		return str + 1;
+	}
+
 	len = _parse_integer(str, 10, &n);
 	if (!len)
 		return ERR_PTR(-EINVAL);
@@ -571,7 +577,9 @@ static const char *bitmap_find_region_reverse(const char *start, const char *end
 
 static const char *bitmap_parse_region(const char *str, struct region *r)
 {
-	str = bitmap_getnum(str, &r->start);
+	unsigned int lastbit = r->nbits - 1;
+
+	str = bitmap_getnum(str, &r->start, lastbit);
 	if (IS_ERR(str))
 		return str;
 
@@ -581,7 +589,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
 	if (*str != '-')
 		return ERR_PTR(-EINVAL);
 
-	str = bitmap_getnum(str + 1, &r->end);
+	str = bitmap_getnum(str + 1, &r->end, lastbit);
 	if (IS_ERR(str))
 		return str;
 
@@ -591,14 +599,14 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
 	if (*str != ':')
 		return ERR_PTR(-EINVAL);
 
-	str = bitmap_getnum(str + 1, &r->off);
+	str = bitmap_getnum(str + 1, &r->off, lastbit);
 	if (IS_ERR(str))
 		return str;
 
 	if (*str != '/')
 		return ERR_PTR(-EINVAL);
 
-	return bitmap_getnum(str + 1, &r->group_len);
+	return bitmap_getnum(str + 1, &r->group_len, lastbit);
 
 no_end:
 	r->end = r->start;
@@ -625,6 +633,10 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
  * From each group will be used only defined amount of bits.
  * Syntax: range:used_size/group_size
  * Example: 0-1023:2/256 ==> 0,1,256,257,512,513,768,769
+ * The value 'N' can be used as a dynamically substituted token for the
+ * maximum allowed value; i.e (nmaskbits - 1).  Keep in mind that it is
+ * dynamic, so if system changes cause the bitmap width to change, such
+ * as more cores in a CPU list, then any ranges using N will also change.
  *
  * Returns: 0 on success, -errno on invalid input strings. Error values:
  *
-- 
2.9.5

[PATCH lib/bitmap 7/9] lib: test_bitmap: add tests for "N" alias

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

These are copies of existing tests, with just 31 --> N.  This ensures
the recently added "N" alias transparently works in any normally
numeric fields of a region specification.

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 lib/test_bitmap.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 3c1c46d..9cd5755 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -353,6 +353,16 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
 	{0, "16-31:16/31",		&exp1[3 * step], 32, 0},
 	{0, "31-31:31/31",		&exp1[14 * step], 32, 0},
 
+	{0, "N-N",			&exp1[14 * step], 32, 0},
+	{0, "0-0:1/N",			&exp1[0], 32, 0},
+	{0, "0-0:N/N",			&exp1[0], 32, 0},
+	{0, "0-15:16/N",		&exp1[2 * step], 32, 0},
+	{0, "15-15:N/N",		&exp1[13 * step], 32, 0},
+	{0, "15-N:1/N",			&exp1[13 * step], 32, 0},
+	{0, "16-N:16/N",		&exp1[3 * step], 32, 0},
+	{0, "N-N:N/N",			&exp1[14 * step], 32, 0},
+
+	{0, "0-N:1/3,1-N:1/3,2-N:1/3",		&exp1[8 * step], 32, 0},
 	{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},
 
-- 
2.9.5

[PATCH lib/bitmap 8/9] rcu: deprecate "all" option to rcu_nocbs=

[paulmck]

From: Paul Gortmaker <paul.gortmaker@windriver.com>

With the core bitmap support now accepting "N" as a placeholder for
the end of the bitmap, "all" can be represented as "0-N" and has the
advantage of not being specific to RCU (or any other subsystem).

So deprecate the use of "all" by removing documentation references
to it.  The support itself needs to remain for now, since we don't
know how many people out there are using it currently, but since it
is in an __init area anyway, it isn't worth losing sleep over.

Cc: Yury Norov <yury.norov@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 4 +---
 kernel/rcu/tree_plugin.h                        | 6 ++----
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0454572..83e2ef1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4068,9 +4068,7 @@
 				see CONFIG_RAS_CEC help text.
 
 	rcu_nocbs=	[KNL]
-			The argument is a cpu list, as described above,
-			except that the string "all" can be used to
-			specify every CPU on the system.
+			The argument is a cpu list, as described above.
 
 			In kernels built with CONFIG_RCU_NOCB_CPU=y, set
 			the specified list of CPUs to be no-callback CPUs.
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 2d60377..0b95562 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1464,14 +1464,12 @@ static void rcu_cleanup_after_idle(void)
 
 /*
  * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
- * The string after the "rcu_nocbs=" is either "all" for all CPUs, or a
- * comma-separated list of CPUs and/or CPU ranges.  If an invalid list is
- * given, a warning is emitted and all CPUs are offloaded.
+ * If the list is invalid, a warning is emitted and all CPUs are offloaded.
  */
 static int __init rcu_nocb_setup(char *str)
 {
 	alloc_bootmem_cpumask_var(&rcu_nocb_mask);
-	if (!strcasecmp(str, "all"))
+	if (!strcasecmp(str, "all"))		/* legacy: use "0-N" instead */
 		cpumask_setall(rcu_nocb_mask);
 	else
 		if (cpulist_parse(str, rcu_nocb_mask)) {
-- 
2.9.5

[PATCH lib/bitmap 9/9] rcutorture: Use "all" and "N" in "nohz_full" and "rcu_nocbs"

[paulmck]

From: "Paul E. McKenney" <paulmck@kernel.org>

This commit uses the shiny new "all" and "N" cpumask options to decouple
the "nohz_full" and "rcu_nocbs" kernel boot parameters in the TREE04.boot
and TREE08.boot files from the CONFIG_NR_CPUS options in the TREE04 and
TREE08 files.

Reported-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot | 2 +-
 tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot
index 5adc675..a8d94ca 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE04.boot
@@ -1 +1 @@
-rcutree.rcu_fanout_leaf=4 nohz_full=1-7
+rcutree.rcu_fanout_leaf=4 nohz_full=1-N
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot
index 22478fd..94d3844 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE08.boot
@@ -1,3 +1,3 @@
 rcupdate.rcu_self_test=1
 rcutree.rcu_fanout_exact=1
-rcu_nocbs=0-7
+rcu_nocbs=all
-- 
2.9.5