From: Brian Silverman <brian@xxxxxxxxxxxxxxxx> 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 746db9443ea57fd9c059f62c4bfbf41cf224fe13 upstream. When non-realtime tasks get priority-inheritance boosted to a realtime scheduling class, RLIMIT_RTTIME starts to apply to them. However, the counter used for checking this (the same one used for SCHED_RR timeslices) was not getting reset. This meant that tasks running with a non-realtime scheduling class which are repeatedly boosted to a realtime one, but never block while they are running realtime, eventually hit the timeout without ever running for a time over the limit. This patch resets the realtime timeslice counter when un-PI-boosting from an RT to a non-RT scheduling class. I have some test code with two threads and a shared PTHREAD_PRIO_INHERIT mutex which induces priority boosting and spins while boosted that gets killed by a SIGXCPU on non-fixed kernels but doesn't with this patch applied. It happens much faster with a CONFIG_PREEMPT_RT kernel, and does happen eventually with PREEMPT_VOLUNTARY kernels. Signed-off-by: Brian Silverman <brian@xxxxxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: austin@xxxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/1424305436-6716-1-git-send-email-brian@xxxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- kernel/sched/core.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f09e22163be3..0030db473c99 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3060,8 +3060,11 @@ void rt_mutex_setprio(struct task_struct *p, int prio) if (rt_prio(prio)) p->sched_class = &rt_sched_class; - else + else { + if (rt_prio(oldprio)) + p->rt.timeout = 0; p->sched_class = &fair_sched_class; + } p->prio = prio; -- 2.3.5 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html