The below patch is an idea proposed by tglx and depends on sched-devel +
the hrtick patch previously posted.
The current watchdog action is to demote the task to SCHED_NORMAL,
however it might be wanted to deliver a signal instead (or have more per
task configuration state). Which is why I added Lennart to the CC list
as I gathered he would like something like this for PulseAudio.
---
Subject: sched: SCHED_FIFO watchdog timer
Set a per task (rlimit based) limit on SCHED_FIFO runtime. When the
limit is exceeded the task is demoted back to SCHED_NORMAL.
Signed-off-by: Peter Zijlstra <[email protected]>
---
include/asm-generic/resource.h | 5 +++--
kernel/sched.c | 5 +++++
kernel/sched_rt.c | 36 ++++++++++++++++++++++++++++++++++++
3 files changed, 44 insertions(+), 2 deletions(-)
Index: linux-2.6/include/asm-generic/resource.h
===================================================================
--- linux-2.6.orig/include/asm-generic/resource.h
+++ linux-2.6/include/asm-generic/resource.h
@@ -44,8 +44,8 @@
#define RLIMIT_NICE 13 /* max nice prio allowed to raise to
0-39 for nice level 19 .. -20 */
#define RLIMIT_RTPRIO 14 /* maximum realtime priority */
-
-#define RLIM_NLIMITS 15
+#define RLIMIT_FIFOTIME 15 /* timeout for fifo slices in us */
+#define RLIM_NLIMITS 16
/*
* SuS says limits have to be unsigned.
@@ -86,6 +86,7 @@
[RLIMIT_MSGQUEUE] = { MQ_BYTES_MAX, MQ_BYTES_MAX }, \
[RLIMIT_NICE] = { 0, 0 }, \
[RLIMIT_RTPRIO] = { 0, 0 }, \
+ [RLIMIT_FIFOTIME] = { RLIM_INFINITY, RLIM_INFINITY }, \
}
#endif /* __KERNEL__ */
Index: linux-2.6/kernel/sched_rt.c
===================================================================
--- linux-2.6.orig/kernel/sched_rt.c
+++ linux-2.6/kernel/sched_rt.c
@@ -89,6 +89,14 @@ static struct task_struct *pick_next_tas
next->se.exec_start = rq->clock;
+ if (next->policy == SCHED_FIFO) {
+ unsigned long fifotime;
+
+ fifotime = rq->curr->signal->rlim[RLIMIT_FIFOTIME].rlim_cur;
+ if (fifotime != RLIM_INFINITY)
+ hrtick_start(rq, (u64)fifotime * 1000, 0);
+ }
+
return next;
}
@@ -194,8 +202,36 @@ load_balance_rt(struct rq *this_rq, int
return load_moved;
}
+#ifdef CONFIG_SCHED_HRT_TICK
+static int fifo_watchdog(struct rq *rq, struct task_struct *p, int queued)
+{
+ if (likely(!queued || p->policy != SCHED_FIFO))
+ return 0;
+
+ /*
+ * task has been naughty, turn into SCHED_NORMAL
+ */
+ printk(KERN_INFO "SCHED_FIFO task %s/%d exceeded his runtime quota,"
+ " demoting to regular task\n", p->comm, task_pid_nr(p));
+ deactivate_task(rq, p, 0);
+ __setscheduler(rq, p, SCHED_NORMAL, 0);
+ activate_task(rq, p, 0);
+ resched_task(p);
+
+ return 1;
+}
+#else
+static inline int fifo_watchdog(struct rq *rq, struct task_struct *p, int queued)
+{
+ return 0;
+}
+#endif
+
static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
{
+ if (fifo_watchdog(rq, p, queued))
+ return;
+
/*
* RR tasks need a special form of timeslice management.
* FIFO tasks have no timeslices.
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -132,6 +132,11 @@ static inline void sg_inc_cpu_power(stru
}
#endif
+static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
+static void activate_task(struct rq *rq, struct task_struct *p, int wakeup);
+static void
+__setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio);
+
static inline int rt_policy(int policy)
{
if (unlikely(policy == SCHED_FIFO) || unlikely(policy == SCHED_RR))
-
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