[3.16.y-ckt stable] Patch "sched: Fix RLIMIT_RTTIME when PI-boosting to RT" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Thu Apr 9 08:58:15 UTC 2015
This is a note to let you know that I have just added a patch titled
sched: Fix RLIMIT_RTTIME when PI-boosting to RT
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt10.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From e3483c8fd278c1d4f5385bdfd68105aa5cc0ff16 Mon Sep 17 00:00:00 2001
From: Brian Silverman <brian at peloton-tech.com>
Date: Wed, 18 Feb 2015 16:23:56 -0800
Subject: sched: Fix RLIMIT_RTTIME when PI-boosting to RT
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 at peloton-tech.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Cc: austin at peloton-tech.com
Link: http://lkml.kernel.org/r/1424305436-6716-1-git-send-email-brian@peloton-tech.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
kernel/sched/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 07f41f4fe4db..2eb2e7992970 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3012,6 +3012,8 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
} else {
if (dl_prio(oldprio))
p->dl.dl_boosted = 0;
+ if (rt_prio(oldprio))
+ p->rt.timeout = 0;
p->sched_class = &fair_sched_class;
}
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