From: Brian Silverman <[email protected]> 3.4.108-rc1 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 <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> [lizf: Backported to 3.4: adjust contest] Signed-off-by: Zefan Li <[email protected]> --- kernel/sched/core.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5701cb9..2f8363e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4031,10 +4031,13 @@ void rt_mutex_setprio(struct task_struct *p, int prio) if (running) p->sched_class->put_prev_task(rq, p); - if (rt_prio(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; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
