Messages in this thread | | | Date | Tue, 21 Nov 2017 09:33:52 -0500 | From | joe.korty@concurre ... | Subject | Re: [PATCH] 4.4.86-rt99: fix sync breakage between nr_cpus_allowed and cpus_allowed |
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On Mon, Nov 20, 2017 at 11:57:51PM -0500, Steven Rostedt wrote: > On Mon, 20 Nov 2017 23:02:07 -0500 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > > Ideally, I would like to stay close to what upstream -rt does. Would > > you be able to backport the 4.11-rt patch? > > > > I'm currently working on releasing 4.9-rt and 4.4-rt with the latest > > backports. I could easily add this one too. > > Speaking of which. I just backported this patch to 4.4-rt. Is this what > you are talking about?
Yes it is. Thanks for finding that! Joe
> >From 1dc89be37874bfc7bb4a0ea7c45492d7db39f62b Mon Sep 17 00:00:00 2001 > From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > Date: Mon, 19 Jun 2017 09:55:47 +0200 > Subject: [PATCH] sched/migrate disable: handle updated task-mask mg-dis > section > > If task's cpumask changes while in the task is in a migrate_disable() > section then we don't react on it after a migrate_enable(). It matters > however if current CPU is no longer part of the cpumask. We also miss > the ->set_cpus_allowed() callback. > This patch fixes it by setting task->migrate_disable_update once we this > "delayed" hook. > This bug was introduced while fixing unrelated issue in > migrate_disable() in v4.4-rt3 (update_migrate_disable() got removed > during that). > > Cc: stable-rt@vger.kernel.org > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> > --- > include/linux/sched.h | 1 > kernel/sched/core.c | 59 ++++++++++++++++++++++++++++++++++++++++++++------ > 2 files changed, 54 insertions(+), 6 deletions(-) > > Index: stable-rt.git/include/linux/sched.h > =================================================================== > --- stable-rt.git.orig/include/linux/sched.h 2017-11-20 23:43:24.214077537 -0500 > +++ stable-rt.git/include/linux/sched.h 2017-11-20 23:43:24.154079278 -0500 > @@ -1438,6 +1438,7 @@ struct task_struct { > unsigned int policy; > #ifdef CONFIG_PREEMPT_RT_FULL > int migrate_disable; > + int migrate_disable_update; > # ifdef CONFIG_SCHED_DEBUG > int migrate_disable_atomic; > # endif > Index: stable-rt.git/kernel/sched/core.c > =================================================================== > --- stable-rt.git.orig/kernel/sched/core.c 2017-11-20 23:43:24.214077537 -0500 > +++ stable-rt.git/kernel/sched/core.c 2017-11-20 23:56:05.071687323 -0500 > @@ -1212,18 +1212,14 @@ void set_cpus_allowed_common(struct task > p->nr_cpus_allowed = cpumask_weight(new_mask); > } > > -void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) > +static void __do_set_cpus_allowed_tail(struct task_struct *p, > + const struct cpumask *new_mask) > { > struct rq *rq = task_rq(p); > bool queued, running; > > lockdep_assert_held(&p->pi_lock); > > - if (__migrate_disabled(p)) { > - cpumask_copy(&p->cpus_allowed, new_mask); > - return; > - } > - > queued = task_on_rq_queued(p); > running = task_current(rq, p); > > @@ -1246,6 +1242,20 @@ void do_set_cpus_allowed(struct task_str > enqueue_task(rq, p, ENQUEUE_RESTORE); > } > > +void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) > +{ > + if (__migrate_disabled(p)) { > + lockdep_assert_held(&p->pi_lock); > + > + cpumask_copy(&p->cpus_allowed, new_mask); > +#if defined(CONFIG_PREEMPT_RT_FULL) && defined(CONFIG_SMP) > + p->migrate_disable_update = 1; > +#endif > + return; > + } > + __do_set_cpus_allowed_tail(p, new_mask); > +} > + > static DEFINE_PER_CPU(struct cpumask, sched_cpumasks); > static DEFINE_MUTEX(sched_down_mutex); > static cpumask_t sched_down_cpumask; > @@ -3231,6 +3241,43 @@ void migrate_enable(void) > */ > p->migrate_disable = 0; > > + if (p->migrate_disable_update) { > + unsigned long flags; > + struct rq *rq; > + > + rq = task_rq_lock(p, &flags); > + update_rq_clock(rq); > + > + __do_set_cpus_allowed_tail(p, &p->cpus_allowed); > + task_rq_unlock(rq, p, &flags); > + > + p->migrate_disable_update = 0; > + > + WARN_ON(smp_processor_id() != task_cpu(p)); > + if (!cpumask_test_cpu(task_cpu(p), &p->cpus_allowed)) { > + const struct cpumask *cpu_valid_mask = cpu_active_mask; > + struct migration_arg arg; > + unsigned int dest_cpu; > + > + if (p->flags & PF_KTHREAD) { > + /* > + * Kernel threads are allowed on online && !active CPUs > + */ > + cpu_valid_mask = cpu_online_mask; > + } > + dest_cpu = cpumask_any_and(cpu_valid_mask, &p->cpus_allowed); > + arg.task = p; > + arg.dest_cpu = dest_cpu; > + > + unpin_current_cpu(); > + preempt_lazy_enable(); > + preempt_enable(); > + stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); > + tlb_migrate_finish(p->mm); > + return; > + } > + } > + > unpin_current_cpu(); > preempt_enable(); > preempt_lazy_enable();
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