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 <mi...@redhat.com> > >> Cc: Peter Zijlstra <pet...@infradead.org> > >> Signed-off-by: Juri Lelli <juri.le...@gmail.com> > >> --- > >> 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
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