[PATCH] sched/deadline: runtime overrun and deadline miss signals

[Claudio Scordino]

From: Juri Lelli <juri.lelli@xxxxxxxxx>

This patch adds the possibility to get the delivery of two signals
whenever there is a runtime overrun or a deadline miss, respectively.
The request is done through the sched_flags field within the sched_attr
structure.

Forward port of https://lkml.org/lkml/2009/10/16/170

Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxx>
Signed-off-by: Claudio Scordino <claudio@xxxxxxxxxxxxxxx>
Signed-off-by: Luca Abeni <luca.abeni@xxxxxxxxxxxxxxx>
Cc: Tommaso Cucinotta <tommaso.cucinotta@xxxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
---
 include/linux/sched.h          |  8 ++++++++
 include/uapi/linux/sched.h     |  2 ++
 kernel/sched/core.c            |  3 ++-
 kernel/sched/deadline.c        | 13 +++++++++++++
 kernel/time/posix-cpu-timers.c | 26 ++++++++++++++++++++++++++
 5 files changed, 51 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0f897df..285d1b4 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -473,11 +473,19 @@ struct sched_dl_entity {
 	 * has not been executed yet. This flag is useful to avoid race
 	 * conditions between the inactive timer handler and the wakeup
 	 * code.
+	 *
+	 * @dl_overrun tells if the task asked to be informed about budget
+	 * overruns.
+	 *
+	 * @dl_dmiss tells if the task asked to be informed about deadline
+	 * misses.
 	 */
 	int				dl_throttled      : 1;
 	int				dl_boosted        : 1;
 	int				dl_yielded        : 1;
 	int				dl_non_contending : 1;
+	int				dl_overrun	  : 1;
+	int				dl_dmiss	  : 1;
 
 	/*
 	 * Bandwidth enforcement timer. Each -deadline task has its
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index e2a6c7b..544be0c 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -48,5 +48,7 @@
  */
 #define SCHED_FLAG_RESET_ON_FORK	0x01
 #define SCHED_FLAG_RECLAIM		0x02
+#define SCHED_FLAG_DL_OVERRUN		0x04
+#define SCHED_FLAG_DL_DMISS		0x08
 
 #endif /* _UAPI_LINUX_SCHED_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 97227df..d79df7a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4041,7 +4041,8 @@ static int __sched_setscheduler(struct task_struct *p,
 	}
 
 	if (attr->sched_flags &
-		~(SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_RECLAIM))
+		~(SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_RECLAIM |
+			SCHED_FLAG_DL_OVERRUN | SCHED_FLAG_DL_DMISS))
 		return -EINVAL;
 
 	/*
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 8d1b946..8c1aa61 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1154,6 +1154,17 @@ static void update_curr_dl(struct rq *rq)
 throttle:
 	if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
 		dl_se->dl_throttled = 1;
+
+		/*
+		 * If requested, inform the user about deadline misses and/or
+		 * runtime overruns.
+		 */
+		if (unlikely(dl_se->flags & SCHED_FLAG_DL_DMISS &&
+			     dl_time_before(dl_se->deadline, rq_clock(rq))))
+			dl_se->dl_dmiss = 1;
+		if (dl_se->flags & SCHED_FLAG_DL_OVERRUN)
+			dl_se->dl_overrun = 1;
+
 		__dequeue_task_dl(rq, curr, 0);
 		if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
 			enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
@@ -2565,6 +2576,8 @@ void __dl_clear_params(struct task_struct *p)
 	dl_se->dl_throttled = 0;
 	dl_se->dl_yielded = 0;
 	dl_se->dl_non_contending = 0;
+	dl_se->dl_overrun = 0;
+	dl_se->dl_dmiss = 0;
 }
 
 bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 8585ad6..f3616c5 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -13,6 +13,7 @@
 #include <linux/tick.h>
 #include <linux/workqueue.h>
 #include <linux/compat.h>
+#include <linux/sched/deadline.h>
 
 #include "posix-timers.h"
 
@@ -790,6 +791,22 @@ check_timers_list(struct list_head *timers,
 	return 0;
 }
 
+static inline void check_dl_overrun(struct task_struct *tsk)
+{
+	if (tsk->dl.dl_overrun) {
+		tsk->dl.dl_overrun = 0;
+		pr_info("runtime overrun: %s[%d]\n",
+				tsk->comm, task_pid_nr(tsk));
+		__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
+	}
+	if (tsk->dl.dl_dmiss) {
+		tsk->dl.dl_dmiss = 0;
+		pr_info("scheduling deadline miss: %s[%d]\n",
+				tsk->comm, task_pid_nr(tsk));
+		__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
+	}
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them off
  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
@@ -803,6 +820,9 @@ static void check_thread_timers(struct task_struct *tsk,
 	u64 expires;
 	unsigned long soft;
 
+	if (dl_task(tsk))
+		check_dl_overrun(tsk);
+
 	/*
 	 * If cputime_expires is zero, then there are no active
 	 * per thread CPU timers.
@@ -905,6 +925,9 @@ static void check_process_timers(struct task_struct *tsk,
 	struct task_cputime cputime;
 	unsigned long soft;
 
+	if (dl_task(tsk))
+		check_dl_overrun(tsk);
+
 	/*
 	 * If cputimer is not running, then there are no active
 	 * process wide timers (POSIX 1.b, itimers, RLIMIT_CPU).
@@ -1110,6 +1133,9 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
 			return 1;
 	}
 
+	if (dl_task(tsk) && (tsk->dl.dl_overrun || tsk->dl.dl_dmiss))
+		return 1;
+
 	return 0;
 }
 
-- 
2.7.4