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sched/deadline: Impose global limits on sched_attr::sched_period 

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190726161357.397880775@infradead.org
This commit is contained in:
Peter Zijlstra 2019-07-26 16:54:10 +02:00
parent 9cc5b86568
commit b4098bfc5e
3 changed files with 38 additions and 2 deletions
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3
include/linux/sched/sysctl.h
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@ -61,6 +61,9 @@ int sched_proc_update_handler(struct ctl_table *table, int write,
extern unsigned int sysctl_sched_rt_period; extern unsigned int sysctl_sched_rt_period;
extern int sysctl_sched_rt_runtime; extern int sysctl_sched_rt_runtime;
extern unsigned int sysctl_sched_dl_period_max;
extern unsigned int sysctl_sched_dl_period_min;
#ifdef CONFIG_UCLAMP_TASK #ifdef CONFIG_UCLAMP_TASK
extern unsigned int sysctl_sched_uclamp_util_min; extern unsigned int sysctl_sched_uclamp_util_min;
extern unsigned int sysctl_sched_uclamp_util_max; extern unsigned int sysctl_sched_uclamp_util_max;

23
kernel/sched/deadline.c
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@ -2634,6 +2634,14 @@ void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
attr->sched_flags = dl_se->flags; attr->sched_flags = dl_se->flags;
} }
/*
* Default limits for DL period; on the top end we guard against small util
* tasks still getting rediculous long effective runtimes, on the bottom end we
* guard against timer DoS.
*/
unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */
unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */
/* /*
* This function validates the new parameters of a -deadline task. * This function validates the new parameters of a -deadline task.
* We ask for the deadline not being zero, and greater or equal * We ask for the deadline not being zero, and greater or equal
@ -2646,6 +2654,8 @@ void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
*/ */
bool __checkparam_dl(const struct sched_attr *attr) bool __checkparam_dl(const struct sched_attr *attr)
{ {
u64 period, max, min;
/* special dl tasks don't actually use any parameter */ /* special dl tasks don't actually use any parameter */
if (attr->sched_flags & SCHED_FLAG_SUGOV) if (attr->sched_flags & SCHED_FLAG_SUGOV)
return true; return true;
@ -2669,12 +2679,21 @@ bool __checkparam_dl(const struct sched_attr *attr)
attr->sched_period & (1ULL << 63)) attr->sched_period & (1ULL << 63))
return false; return false;
period = attr->sched_period;
if (!period)
period = attr->sched_deadline;
/* runtime <= deadline <= period (if period != 0) */ /* runtime <= deadline <= period (if period != 0) */
if ((attr->sched_period != 0 && if (period < attr->sched_deadline ||
attr->sched_period < attr->sched_deadline) ||
attr->sched_deadline < attr->sched_runtime) attr->sched_deadline < attr->sched_runtime)
return false; return false;
max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
if (period < min || period > max)
return false;
return true; return true;
} }

14
kernel/sysctl.c
View File

@ -1779,6 +1779,20 @@ static struct ctl_table kern_table[] = {
.mode = 0644, .mode = 0644,
.proc_handler = sched_rt_handler, .proc_handler = sched_rt_handler,
}, },
{
.procname = "sched_deadline_period_max_us",
.data = &sysctl_sched_dl_period_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "sched_deadline_period_min_us",
.data = &sysctl_sched_dl_period_min,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{ {
.procname = "sched_rr_timeslice_ms", .procname = "sched_rr_timeslice_ms",
.data = &sysctl_sched_rr_timeslice, .data = &sysctl_sched_rr_timeslice,