Commit b4098bfc authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

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



Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190726161357.397880775@infradead.org
parent 9cc5b865

include/linux/sched/sysctl.h

+3 −0
Original line number Diff line number Diff line
@@ -61,6 +61,9 @@ int sched_proc_update_handler(struct ctl_table *table, int write, 
extern unsigned int sysctl_sched_rt_period;

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

extern unsigned int sysctl_sched_uclamp_util_min;

extern unsigned int sysctl_sched_uclamp_util_max;

kernel/sched/deadline.c

+21 −2
Original line number Diff line number Diff line
@@ -2634,6 +2634,14 @@ void __getparam_dl(struct task_struct *p, struct sched_attr *attr) 
	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.

 * 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)

{

	u64 period, max, min;



	/* special dl tasks don't actually use any parameter */

	if (attr->sched_flags & SCHED_FLAG_SUGOV)

		return true;
@@ -2669,12 +2679,21 @@ bool __checkparam_dl(const struct sched_attr *attr) 
	    attr->sched_period & (1ULL << 63))

		return false;



	period = attr->sched_period;

	if (!period)

		period = attr->sched_deadline;



	/* runtime <= deadline <= period (if period != 0) */

	if ((attr->sched_period != 0 &&

	     attr->sched_period < attr->sched_deadline) ||

	if (period < attr->sched_deadline ||

	    attr->sched_deadline < attr->sched_runtime)

		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;

}

kernel/sysctl.c

+14 −0
Original line number Diff line number Diff line
@@ -1779,6 +1779,20 @@ static struct ctl_table kern_table[] = { 
		.mode		= 0644,

		.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",

		.data		= &sysctl_sched_rr_timeslice,