Don't compare sysctl_sched_rt_runtime against sysctl_sched_rt_period if
the former is equal to RUNTIME_INF, otherwise disabling -rt bandwidth
management always fails.
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Juri Lelli <[email protected]>
---
kernel/sched/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 210a12a..5c0a304 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7477,7 +7477,8 @@ static int sched_rt_global_validate(void)
if (sysctl_sched_rt_period <= 0)
return -EINVAL;
- if (sysctl_sched_rt_runtime > sysctl_sched_rt_period)
+ if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
+ (sysctl_sched_rt_runtime > sysctl_sched_rt_period))
return -EINVAL;
return 0;
--
1.7.9.5
On Fri, Jan 31, 2014 at 05:43:27PM +0100, Juri Lelli wrote:
> Don't compare sysctl_sched_rt_runtime against sysctl_sched_rt_period if
> the former is equal to RUNTIME_INF, otherwise disabling -rt bandwidth
> management always fails.
>
> Cc: Ingo Molnar <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Signed-off-by: Juri Lelli <[email protected]>
> ---
> kernel/sched/core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 210a12a..5c0a304 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7477,7 +7477,8 @@ static int sched_rt_global_validate(void)
> if (sysctl_sched_rt_period <= 0)
> return -EINVAL;
>
> - if (sysctl_sched_rt_runtime > sysctl_sched_rt_period)
> + if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
> + (sysctl_sched_rt_runtime > sysctl_sched_rt_period))
> return -EINVAL;
Won't this be caught by the test above?
#define RUNTIME_INF ((u64)~0ULL)
which means that if sysctl_sched_rt_runtime is set to RUNTIME_INF, it will
trigger on the previous test, and the first part of this test will always
be true.
Or have I suffered catastrophic monday-morning braindamage?
--
Henrik Austad
On 02/03/2014 10:53 AM, Henrik Austad wrote:
> On Fri, Jan 31, 2014 at 05:43:27PM +0100, Juri Lelli wrote:
>> Don't compare sysctl_sched_rt_runtime against sysctl_sched_rt_period if
>> the former is equal to RUNTIME_INF, otherwise disabling -rt bandwidth
>> management always fails.
>>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: Peter Zijlstra <[email protected]>
>> Signed-off-by: Juri Lelli <[email protected]>
>> ---
>> kernel/sched/core.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 210a12a..5c0a304 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -7477,7 +7477,8 @@ static int sched_rt_global_validate(void)
>> if (sysctl_sched_rt_period <= 0)
>> return -EINVAL;
>>
>> - if (sysctl_sched_rt_runtime > sysctl_sched_rt_period)
>> + if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
>> + (sysctl_sched_rt_runtime > sysctl_sched_rt_period))
>> return -EINVAL;
>
> Won't this be caught by the test above?
>
> #define RUNTIME_INF ((u64)~0ULL)
>
> which means that if sysctl_sched_rt_runtime is set to RUNTIME_INF, it will
> trigger on the previous test, and the first part of this test will always
> be true.
>
> Or have I suffered catastrophic monday-morning braindamage?
>
As I understand it. When you do
echo -1 > /proc/sys/kernel/sched_rt_runtime_us
sysctl_sched_rt_runtime is actually set to -1 (being an int).
But then you compare it against and unsigned int, so the cast converts it to
actually be RUNTIME_INF, and thus greater than sysctl_sched_rt_period (so the
function returns -EINVAL, while you'd want it to return 0, as you are disabling
-rt throttling).
Makes sense?
Thanks,
- Juri
On Mon, Feb 03, 2014 at 11:14:05AM +0100, Juri Lelli wrote:
> On 02/03/2014 10:53 AM, Henrik Austad wrote:
> > On Fri, Jan 31, 2014 at 05:43:27PM +0100, Juri Lelli wrote:
> >> Don't compare sysctl_sched_rt_runtime against sysctl_sched_rt_period if
> >> the former is equal to RUNTIME_INF, otherwise disabling -rt bandwidth
> >> management always fails.
> >>
> >> Cc: Ingo Molnar <[email protected]>
> >> Cc: Peter Zijlstra <[email protected]>
> >> Signed-off-by: Juri Lelli <[email protected]>
> >> ---
> >> kernel/sched/core.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> >> index 210a12a..5c0a304 100644
> >> --- a/kernel/sched/core.c
> >> +++ b/kernel/sched/core.c
> >> @@ -7477,7 +7477,8 @@ static int sched_rt_global_validate(void)
> >> if (sysctl_sched_rt_period <= 0)
> >> return -EINVAL;
> >>
> >> - if (sysctl_sched_rt_runtime > sysctl_sched_rt_period)
> >> + if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
> >> + (sysctl_sched_rt_runtime > sysctl_sched_rt_period))
> >> return -EINVAL;
> >
> > Won't this be caught by the test above?
> >
> > #define RUNTIME_INF ((u64)~0ULL)
> >
> > which means that if sysctl_sched_rt_runtime is set to RUNTIME_INF, it will
> > trigger on the previous test, and the first part of this test will always
> > be true.
> >
> > Or have I suffered catastrophic monday-morning braindamage?
> >
>
> As I understand it. When you do
>
> echo -1 > /proc/sys/kernel/sched_rt_runtime_us
>
> sysctl_sched_rt_runtime is actually set to -1 (being an int).
Yes.
> But then you compare it against and unsigned int, so the cast converts it to
> actually be RUNTIME_INF, and thus greater than sysctl_sched_rt_period (so the
> function returns -EINVAL, while you'd want it to return 0, as you are disabling
> -rt throttling).
Ah, yes, it comes down to my early-monday brain hemorrhage, mixing up
rt_period and rt_runtime. My apologies!
> Makes sense?
Yes it does.
--
Henrik Austad