Messages in this thread Patch in this message | | | From | Rakib Mullick <> | Subject | [PATCH] Fix isocpus's param handling when CPUMASK_OFFSTACK=n. | Date | Sat, 21 Oct 2017 13:10:17 +0600 |
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> *On Fri, Oct 20, 2017 at 2:49 PM, Ingo Molnar <mingo@kernel.org> wrote: > >> Rakib Mullick <rakib.mullick@gmail.com> wrote: >> include/linux/cpumask.h | 16 ++++++++++++++++ >> kernel/sched/topology.c | 8 +++++--- >> 2 files changed, 21 insertions(+), 3 deletions(-) > > What kernel is this against? It does not apply to the latest kernels.
It was against 4.14-rc4, prepared before -rc5 release. Please, consider the below one, against -rc5.
cpulist_parse() uses nr_cpumask_bits as limit to parse the passed buffer from kernel commandline. What nr_cpumask_bits represents varies depends upon CONFIG_CPUMASK_OFFSTACK option. If CONFIG_CPUMASK_OFFSTACK=n, then nr_cpumask_bits is same as NR_CPUS, which might not represent the # of cpus really exist (default 64). So, there's a chance of gap between nr_cpu_ids and NR_CPUS, which ultimately lead towards invalid cpulist_parse() operation. For example, if isolcpus=9 is passed on a 8 cpu system (CONFIG_CPUMASK_OFFSTACK=n) it doesn't show the error that it suppose to.
This patch fixes this issue by effectively find out the last cpu of the passed isolcpus list and checking it with nr_cpu_ids. Also, fixes the error message where the nr_cpu_ids should be nr_cpu_ids-1, since the cpu numbering starts from 0.
Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com> --- include/linux/cpumask.h | 16 ++++++++++++++++ kernel/sched/topology.c | 8 +++++--- 2 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index cd415b7..5631725 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 f1cf4f3..b9265c8 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -466,12 +466,14 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu) /* Setup the mask of CPUs configured for isolated domains */ static int __init isolated_cpu_setup(char *str) { - int ret; + int ret, lastcpu; 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); + lastcpu = cpumask_last(cpu_isolated_map); + if (ret || lastcpu >= nr_cpu_ids) { + pr_err("sched: Error, all isolcpus= values must be between 0 and %u\n", + nr_cpu_ids-1); return 0; } return 1; -- 2.9.3
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