[Xenomai] [PATCH] boilerplate/setup: cobalt: do not advertise non-RT CPUs to applications

[Xenomai] [PATCH] boilerplate/setup: cobalt: do not advertise non-RT CPUs to applications

[Philippe Gerum]

The CPU affinity mask in __base_setup_data.cpu_affinity - which may be
set by --cpu-affinity - is conventionally checked by applications for
determining which CPUs are usable for real-time duties.

Over Cobalt, we need to make sure that such mask reflects the set of
CPUs available for running real-time threads as defined by the core
(i.e. /proc/xenomai/affinity), in absence of --cpu-affinity
setting.

Otherwise, some applications like switchest looking at an empty
affinity mask may wrongly assume that all CPUs are available for
running RT threads, leading to a failure when manually pinning such
thread to an invalid (non-RT) CPU.

With current Cobalt core and I-pipe releases not fixed for gracefully
handling invalid domain migration requests over a non-RT CPU, such a
failure may trigger a kernel panic.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>
---
 lib/boilerplate/setup.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/lib/boilerplate/setup.c b/lib/boilerplate/setup.c
index 8b363efee..3214d7f04 100644
--- a/lib/boilerplate/setup.c
+++ b/lib/boilerplate/setup.c
@@ -173,6 +173,8 @@ static int collect_cpu_affinity(const char *cpu_list)
 		return ret;
 	}
 
+	CPU_ZERO(&__base_setup_data.cpu_affinity);
+
 	s = n = strdup(cpu_list);
 	while ((range = strtok_r(n, ",", &range_p)) != NULL) {
 		if (*range == '\0')
@@ -232,6 +234,33 @@ fail:
 	return -EINVAL;
 }
 
+static void retrieve_default_cpu_affinity(void)
+{
+	CPU_ZERO(&__base_setup_data.cpu_affinity);
+
+#ifdef CONFIG_XENO_COBALT
+	/*
+	 * If the Cobalt core has restricted the CPU set, update our
+	 * mask accordingly.
+	 */
+	unsigned long cpumask;
+	FILE *fp;
+	int cpu;
+
+	fp = fopen("/proc/xenomai/affinity", "r");
+	if (fp == NULL)
+		return;	/* uhh? */
+
+	if (fscanf(fp, "%lx", &cpumask) == 1) {
+		for (cpu = 0; cpumask; cpumask >>= 1, cpu++)
+			if (cpumask & 1)
+				CPU_SET(cpu, &__base_setup_data.cpu_affinity);
+	}
+
+	fclose(fp);
+#endif
+}
+
 static inline char **prep_args(int argc, char *const argv[])
 {
 	char **uargv;
@@ -528,8 +557,8 @@ static void __xenomai_init(int *argcp, char *const **argvp, const char *me)
 	/* No ifs, no buts: we must be called over the main thread. */
 	assert(getpid() == __node_id);
 
-	/* Define default CPU affinity, i.e. no particular affinity. */
-	CPU_ZERO(&__base_setup_data.cpu_affinity);
+	/* Retrieve the default CPU affinity. */
+	retrieve_default_cpu_affinity();
 
 	/*
 	 * Parse the base options first, to bootstrap the core with
-- 
2.14.4

Re: [Xenomai] [PATCH] boilerplate/setup: cobalt: do not advertise non-RT CPUs to applications

[Jan Kiszka]

On 14.10.18 10:54, Philippe Gerum wrote:
> The CPU affinity mask in __base_setup_data.cpu_affinity - which may be
> set by --cpu-affinity - is conventionally checked by applications for
> determining which CPUs are usable for real-time duties.
> 
> Over Cobalt, we need to make sure that such mask reflects the set of
> CPUs available for running real-time threads as defined by the core
> (i.e. /proc/xenomai/affinity), in absence of --cpu-affinity
> setting.
> 
> Otherwise, some applications like switchest looking at an empty
> affinity mask may wrongly assume that all CPUs are available for
> running RT threads, leading to a failure when manually pinning such
> thread to an invalid (non-RT) CPU.
> 
> With current Cobalt core and I-pipe releases not fixed for gracefully
> handling invalid domain migration requests over a non-RT CPU, such a
> failure may trigger a kernel panic.
> 
> Signed-off-by: Philippe Gerum <rpm@xenomai.org>
> ---
>   lib/boilerplate/setup.c | 33 +++++++++++++++++++++++++++++++--
>   1 file changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/boilerplate/setup.c b/lib/boilerplate/setup.c
> index 8b363efee..3214d7f04 100644
> --- a/lib/boilerplate/setup.c
> +++ b/lib/boilerplate/setup.c
> @@ -173,6 +173,8 @@ static int collect_cpu_affinity(const char *cpu_list)
>   		return ret;
>   	}
>   
> +	CPU_ZERO(&__base_setup_data.cpu_affinity);
> +
>   	s = n = strdup(cpu_list);
>   	while ((range = strtok_r(n, ",", &range_p)) != NULL) {
>   		if (*range == '\0')
> @@ -232,6 +234,33 @@ fail:
>   	return -EINVAL;
>   }
>   
> +static void retrieve_default_cpu_affinity(void)
> +{
> +	CPU_ZERO(&__base_setup_data.cpu_affinity);
> +
> +#ifdef CONFIG_XENO_COBALT
> +	/*
> +	 * If the Cobalt core has restricted the CPU set, update our
> +	 * mask accordingly.
> +	 */
> +	unsigned long cpumask;
> +	FILE *fp;
> +	int cpu;
> +
> +	fp = fopen("/proc/xenomai/affinity", "r");
> +	if (fp == NULL)
> +		return;	/* uhh? */
> +
> +	if (fscanf(fp, "%lx", &cpumask) == 1) {
> +		for (cpu = 0; cpumask; cpumask >>= 1, cpu++)
> +			if (cpumask & 1)
> +				CPU_SET(cpu, &__base_setup_data.cpu_affinity);
> +	}
> +
> +	fclose(fp);
> +#endif
> +}
> +
>   static inline char **prep_args(int argc, char *const argv[])
>   {
>   	char **uargv;
> @@ -528,8 +557,8 @@ static void __xenomai_init(int *argcp, char *const **argvp, const char *me)
>   	/* No ifs, no buts: we must be called over the main thread. */
>   	assert(getpid() == __node_id);
>   
> -	/* Define default CPU affinity, i.e. no particular affinity. */
> -	CPU_ZERO(&__base_setup_data.cpu_affinity);
> +	/* Retrieve the default CPU affinity. */
> +	retrieve_default_cpu_affinity();
>   
>   	/*
>   	 * Parse the base options first, to bootstrap the core with
> 

Thanks, applied to next.

Am I right that this as well as most of the patches in the original series are 
also stable candidates?

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

Re: [Xenomai] [PATCH] boilerplate/setup: cobalt: do not advertise non-RT CPUs to applications

[Philippe Gerum]

On 10/17/2018 01:19 PM, Jan Kiszka wrote:
> On 14.10.18 10:54, Philippe Gerum wrote:
>> The CPU affinity mask in __base_setup_data.cpu_affinity - which may be
>> set by --cpu-affinity - is conventionally checked by applications for
>> determining which CPUs are usable for real-time duties.
>>
>> Over Cobalt, we need to make sure that such mask reflects the set of
>> CPUs available for running real-time threads as defined by the core
>> (i.e. /proc/xenomai/affinity), in absence of --cpu-affinity
>> setting.
>>
>> Otherwise, some applications like switchest looking at an empty
>> affinity mask may wrongly assume that all CPUs are available for
>> running RT threads, leading to a failure when manually pinning such
>> thread to an invalid (non-RT) CPU.
>>
>> With current Cobalt core and I-pipe releases not fixed for gracefully
>> handling invalid domain migration requests over a non-RT CPU, such a
>> failure may trigger a kernel panic.
>>
>> Signed-off-by: Philippe Gerum <rpm@xenomai.org>
>> ---
>>   lib/boilerplate/setup.c | 33 +++++++++++++++++++++++++++++++--
>>   1 file changed, 31 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/boilerplate/setup.c b/lib/boilerplate/setup.c
>> index 8b363efee..3214d7f04 100644
>> --- a/lib/boilerplate/setup.c
>> +++ b/lib/boilerplate/setup.c
>> @@ -173,6 +173,8 @@ static int collect_cpu_affinity(const char *cpu_list)
>>           return ret;
>>       }
>>   +    CPU_ZERO(&__base_setup_data.cpu_affinity);
>> +
>>       s = n = strdup(cpu_list);
>>       while ((range = strtok_r(n, ",", &range_p)) != NULL) {
>>           if (*range == '\0')
>> @@ -232,6 +234,33 @@ fail:
>>       return -EINVAL;
>>   }
>>   +static void retrieve_default_cpu_affinity(void)
>> +{
>> +    CPU_ZERO(&__base_setup_data.cpu_affinity);
>> +
>> +#ifdef CONFIG_XENO_COBALT
>> +    /*
>> +     * If the Cobalt core has restricted the CPU set, update our
>> +     * mask accordingly.
>> +     */
>> +    unsigned long cpumask;
>> +    FILE *fp;
>> +    int cpu;
>> +
>> +    fp = fopen("/proc/xenomai/affinity", "r");
>> +    if (fp == NULL)
>> +        return;    /* uhh? */
>> +
>> +    if (fscanf(fp, "%lx", &cpumask) == 1) {
>> +        for (cpu = 0; cpumask; cpumask >>= 1, cpu++)
>> +            if (cpumask & 1)
>> +                CPU_SET(cpu, &__base_setup_data.cpu_affinity);
>> +    }
>> +
>> +    fclose(fp);
>> +#endif
>> +}
>> +
>>   static inline char **prep_args(int argc, char *const argv[])
>>   {
>>       char **uargv;
>> @@ -528,8 +557,8 @@ static void __xenomai_init(int *argcp, char *const
>> **argvp, const char *me)
>>       /* No ifs, no buts: we must be called over the main thread. */
>>       assert(getpid() == __node_id);
>>   -    /* Define default CPU affinity, i.e. no particular affinity. */
>> -    CPU_ZERO(&__base_setup_data.cpu_affinity);
>> +    /* Retrieve the default CPU affinity. */
>> +    retrieve_default_cpu_affinity();
>>         /*
>>        * Parse the base options first, to bootstrap the core with
>>
> 
> Thanks, applied to next.
> 
> Am I right that this as well as most of the patches in the original
> series are also stable candidates?
> 

I believe so.

-- 
Philippe.