[PATCH 2/4] cpumask: make "all" alias global and not just RCU

Paul Gortmaker
2020-11-08T16:08:14Z

It is probably better that we don't have subsystem specific
abbreviations or aliases for generic CPU list specifications.

Hence we move the "all" from RCU out to lib/ so that it can be
used in any instance where CPU lists are being parsed.

Signed-off-by: Paul Gortmaker <paul.gortmaker-CWA4WttNNZF54TAoqtyWWQ@public.gmane.org>
---
Documentation/admin-guide/kernel-parameters.rst | 7 +++++++
Documentation/admin-guide/kernel-parameters.txt | 4 +---
kernel/rcu/tree_plugin.h | 13 ++++---------
lib/cpumask.c | 6 ++++++
4 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
index 6d421694d98e..ef98ca700946 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 following convenience aliases are also accepted and used:
+
+ foo_cpus=all
+
+is equivalent to "foo_cpus=0-N" -- where "N" is the numerically last CPU on
+the system, thus avoiding looking up the value in "/sys/devices/system/cpu"
+in advance on each deployed system.

This document may not be entirely up to date and comprehensive. The command
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 526d65d8573a..96eed72f02a2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4023,9 +4023,7 @@
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 fd8a52e9a887..b18f89f94fd3 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1463,20 +1463,15 @@ 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 (cpulist_parse(str, rcu_nocb_mask)) {
+ pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
cpumask_setall(rcu_nocb_mask);
- else
- if (cpulist_parse(str, rcu_nocb_mask)) {
- pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
- cpumask_setall(rcu_nocb_mask);
- }
+ }
return 1;
}
__setup("rcu_nocbs=", rcu_nocb_setup);
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 5eb002237404..15599cdf5db6 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -2,6 +2,7 @@
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/bitops.h>
+#include <linux/string.h>
#include <linux/cpumask.h>
#include <linux/export.h>
#include <linux/memblock.h>
@@ -104,6 +105,11 @@ EXPORT_SYMBOL(cpumask_next_wrap);
*/
int cpulist_parse(const char *buf, struct cpumask *dstp)
{
+ if (!strcmp(buf, "all")) {
+ cpumask_setall(dstp);
+ return 0;