Commit-ID: e22cdc3fc5991956146b9856d36b4971fe54dcd6
Gitweb: https://git.kernel.org/tip/e22cdc3fc5991956146b9856d36b4971fe54dcd6
Author: Rakib Mullick <rakib.mullick@xxxxxxxxx>
AuthorDate: Mon, 23 Oct 2017 19:01:54 +0600
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 24 Oct 2017 11:47:25 +0200
sched/isolcpus: Fix "isolcpus=" boot parameter handling when !CONFIG_CPUMASK_OFFSTACK
cpulist_parse() uses nr_cpumask_bits as a limit to parse the
passed buffer from kernel commandline. What nr_cpumask_bits
represents varies depending upon the CONFIG_CPUMASK_OFFSTACK option:
- If CONFIG_CPUMASK_OFFSTACK=n, then nr_cpumask_bits is the same as
NR_CPUS, which might not represent the # of CPUs that really exist
(default 64). So, there's a chance of a gap between nr_cpu_ids
and NR_CPUS, which ultimately lead towards invalid cpulist_parse()
operation. For example, if isolcpus=9 is passed on an 8 cpu
system (CONFIG_CPUMASK_OFFSTACK=n) it doesn't show the error
that it's supposed to.
This patch fixes this bug by finding the last CPU of the passed
isolcpus= list and checking it against nr_cpu_ids.
It also fixes the error message where the nr_cpu_ids should be
nr_cpu_ids-1, since CPU numbering starts from 0.
Signed-off-by: Rakib Mullick <rakib.mullick@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: adobriyan@xxxxxxxxx
Cc: akpm@xxxxxxxxxxxxxxxxxxxx
Cc: longman@xxxxxxxxxx
Cc: mka@xxxxxxxxxxxx
Cc: tj@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20171023130154.9050-1-rakib.mullick@xxxxxxxxx
[ Enhanced the changelog and the kernel message. ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
include/linux/cpumask.h | 16 ++++++++++++++++
kernel/sched/topology.c | 4 ++--
2 files changed, 18 insertions(+), 2 deletions(-)
---
include/linux/cpumask.h | 16 ++++++++++++++++
kernel/sched/topology.c | 4 ++--
2 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index cd415b7..63661de 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -130,6 +130,11 @@ static inline unsigned int cpumask_first(const struct cpumask *srcp)
return 0;
}
+static inline unsigned int cpumask_last(const struct cpumask *srcp)
+{
+ return 0;
+}
+
/* Valid inputs for n are -1 and 0. */
static inline unsigned int cpumask_next(int n, const struct cpumask *srcp)
{
@@ -178,6 +183,17 @@ static inline unsigned int cpumask_first(const struct cpumask *srcp)
return find_first_bit(cpumask_bits(srcp), nr_cpumask_bits);
}
+/**
+ * cpumask_last - get the last CPU in a cpumask
+ * @srcp: - the cpumask pointer
+ *
+ * Returns >= nr_cpumask_bits if no CPUs set.
+ */
+static inline unsigned int cpumask_last(const struct cpumask *srcp)
+{
+ return find_last_bit(cpumask_bits(srcp), nr_cpumask_bits);
+}
+
unsigned int cpumask_next(int n, const struct cpumask *srcp);
/**
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index e50450c..e3d31b0 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -476,8 +476,8 @@ static int __init isolated_cpu_setup(char *str)
alloc_bootmem_cpumask_var(&cpu_isolated_map);
ret = cpulist_parse(str, cpu_isolated_map);
- if (ret) {
- pr_err("sched: Error, all isolcpus= values must be between 0 and %u\n", nr_cpu_ids);
+ if (ret || cpumask_last(cpu_isolated_map) >= nr_cpu_ids) {
+ pr_err("sched: Error, all isolcpus= values must be between 0 and %u - ignoring them.\n", nr_cpu_ids-1);
return 0;
}
return 1;
--
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