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

diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 660ac49f2b531de7ccc7324929273da90477b9a0..24be30a4081450e422cd7c038771f0adb31aea1e 100644 (file)
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -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;

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 504d2f51b0d6300d953a86cadf6922fcf30a57e9..f31964ad9c2efbbf17a4db431451ea50e462e62e 100644 (file)
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -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;
 }
 

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index db1ce7af25632d72f116f16f82c83fca090b82d4..4aea67d3d55263981fdb558b4ec0d6f92e893e54 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -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,