Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757450AbbEVJCU (ORCPT ); Fri, 22 May 2015 05:02:20 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35448 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757347AbbEVJAj (ORCPT ); Fri, 22 May 2015 05:00:39 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "Peter Zijlstra (Intel)" , Linus Torvalds , Mike Galbraith , Stefan Bader , Ingo Molnar , Luis Henriques Subject: [PATCH 3.16.y-ckt 127/129] sched/autogroup: Fix failure to set cpu.rt_runtime_us Date: Fri, 22 May 2015 09:58:32 +0100 Message-Id: <1432285114-9254-128-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1432285114-9254-1-git-send-email-luis.henriques@canonical.com> References: <1432285114-9254-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3355 Lines: 87 3.16.7-ckt12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit 1fe89e1b6d270aa0d3452c60d38461ea589594e3 upstream. Because task_group() uses a cache of autogroup_task_group(), whose output depends on sched_class, switching classes can generate problems. In particular, when started as fair, the cache points to the autogroup, so when switching to RT the tg_rt_schedulable() test fails for every cpu.rt_{runtime,period}_us change because now the autogroup has tasks and no runtime. Furthermore, going back to the previous semantics of varying task_group() with sched_class has the down-side that the sched_debug output varies as well, even though the task really is in the autogroup. Therefore add an autogroup exception to tg_has_rt_tasks() -- such that both (all) task_group() usages in sched/core now have one. And remove all the remnants of the variable task_group() output. Reported-by: Zefan Li Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Stefan Bader Fixes: 8323f26ce342 ("sched: Fix race in task_group()") Link: http://lkml.kernel.org/r/20150209112237.GR5029@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar [ luis: backported to 3.16: adjusted context ] Signed-off-by: Luis Henriques --- kernel/sched/auto_group.c | 6 +----- kernel/sched/core.c | 6 ++++++ 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c index e73efba98301..798e912842d5 100644 --- a/kernel/sched/auto_group.c +++ b/kernel/sched/auto_group.c @@ -87,8 +87,7 @@ static inline struct autogroup *autogroup_create(void) * so we don't have to move tasks around upon policy change, * or flail around trying to allocate bandwidth on the fly. * A bandwidth exception in __sched_setscheduler() allows - * the policy change to proceed. Thereafter, task_group() - * returns &root_task_group, so zero bandwidth is required. + * the policy change to proceed. */ free_rt_sched_group(tg); tg->rt_se = root_task_group.rt_se; @@ -115,9 +114,6 @@ bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) if (tg != &root_task_group) return false; - if (p->sched_class != &fair_sched_class) - return false; - /* * We can only assume the task group can't go away on us if * autogroup_move_group() can see us on ->thread_group list. diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 847922e4ba67..6356f644a47b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7348,6 +7348,12 @@ static inline int tg_has_rt_tasks(struct task_group *tg) { struct task_struct *g, *p; + /* + * Autogroups do not have RT tasks; see autogroup_create(). + */ + if (task_group_is_autogroup(tg)) + return 0; + do_each_thread(g, p) { if (rt_task(p) && task_rq(p)->rt.tg == tg) return 1; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/