[PATCH] Fix isocpus's param handling when CPUMASK_OFFSTACK=n.

[PATCH] Fix isocpus's param handling when CPUMASK_OFFSTACK=n.

[Rakib Mullick]

 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 2404ad2..f9a7c9b 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)
 {
@@ -179,6 +184,17 @@ static inline unsigned int cpumask_first(const struct cpumask *srcp)
 }
 
 /**
+ * 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);
+}
+
+/**
  * cpumask_next - get the next cpu in a cpumask
  * @n: the cpu prior to the place to search (ie. return will be > @n)
  * @srcp: the cpumask pointer
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 1b0b4fb..55b5e09 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -452,12 +452,14 @@ 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 %d\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 %d\n",
+				nr_cpu_ids-1);
 		return 0;
 	}
 	return 1;
-- 
2.9.3

Re: [PATCH] Fix isocpus's param handling when CPUMASK_OFFSTACK=n.

[Ingo Molnar]

* Rakib Mullick <rakib.mullick@gmail.com> wrote:

>  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(-)

What kernel is this against? It does not apply to the latest kernels.

Thanks,

	Ingo

[PATCH] Fix isocpus's param handling when CPUMASK_OFFSTACK=n.

[Rakib Mullick]

>  *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

Re: [PATCH] Fix isocpus's param handling when CPUMASK_OFFSTACK=n.

[Ingo Molnar]

* Rakib Mullick <rakib.mullick@gmail.com> wrote:

> >  *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

Please capitalize 'CPU' properly in documentation.

> + * @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) {

Any reason why 'lastcpu' has to be introduced - why not just use cpumask_last() 
directly in the condition? It looks obvious enough of a pattern.

> +		pr_err("sched: Error, all isolcpus= values must be between 0 and %u\n",
> +				nr_cpu_ids-1);

Please don't break the line mindlessly just due to checkpatch complaining - it 
makes the code less readable.

Thanks,

	Ingo

[PATCH] Fix isocpus's param handling when CPUMASK_OFFSTACK=n.

[Rakib Mullick]

> On Mon, Oct 23, 2017 at 5:50 PM, Ingo Molnar <mingo@kernel.org> wrote:
>
>> * Rakib Mullick <rakib.mullick@gmail.com> wrote:
>> +/**
>> + * cpumask_last - get the last cpu in a cpumask
>
> Please capitalize 'CPU' properly in documentation.
>
OK.
>> +     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) {
>
> Any reason why 'lastcpu' has to be introduced - why not just use cpumask_last()
> directly in the condition? It looks obvious enough of a pattern.
Thought it reflects what we're doing here, but yes, actually it's redundant.

>> +             pr_err("sched: Error, all isolcpus= values must be between 0 and %u\n",
>> +                             nr_cpu_ids-1);
>
> Please don't break the line mindlessly just due to checkpatch complaining - it
> makes the code less readable.
>
Yes, right, mindlessly followed what checkpatch was complaining.

Please see the following patch, with changes made based on your review and
patched up against -rc6.

Thanks,
Rakib
---

[PATCH](v1) Fix isocpus's param handling when CPUMASK_OFFSTACK=n.

 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.

Changes since v0 (Ingo):
	* use cpumask_last() directly into the condition.
	* use CPU rather cpu in documentation
	* undo line break

Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
---
 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 f1cf4f3..060cee5 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -470,8 +470,8 @@ 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\n", nr_cpu_ids-1);
 		return 0;
 	}
 	return 1;
-- 
2.9.3

[tip:sched/core] sched/isolcpus: Fix "isolcpus=" boot parameter handling when !CONFIG_CPUMASK_OFFSTACK

[tip-bot for Rakib Mullick]

Commit-ID:  e22cdc3fc5991956146b9856d36b4971fe54dcd6
Gitweb:     https://git.kernel.org/tip/e22cdc3fc5991956146b9856d36b4971fe54dcd6
Author:     Rakib Mullick <rakib.mullick@gmail.com>
AuthorDate: Mon, 23 Oct 2017 19:01:54 +0600
Committer:  Ingo Molnar <mingo@kernel.org>
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@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: adobriyan@gmail.com
Cc: akpm@linux-foundation.org
Cc: longman@redhat.com
Cc: mka@chromium.org
Cc: tj@kernel.org
Link: http://lkml.kernel.org/r/20171023130154.9050-1-rakib.mullick@gmail.com
[ Enhanced the changelog and the kernel message. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

 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;