lkml.org 
[lkml]   [2015]   [Mar]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH RESEND v10] sched/deadline: support dl task migration during cpu hotplug
    Hi Juri,
    On Tue, Mar 24, 2015 at 09:27:09AM +0000, Juri Lelli wrote:
    >Hi,
    >
    >On 23/03/2015 08:55, Peter Zijlstra wrote:
    >> On Mon, Mar 23, 2015 at 08:25:04AM +0100, Ingo Molnar wrote:
    >>>>>>>>>> + if (cpu >= nr_cpu_ids) {
    >>>>>>>>>> + if (dl_bandwidth_enabled()) {
    >>>>>>>>>> + /*
    >>>>>>>>>> + * Fail to find any suitable cpu.
    >>>>>>>>>> + * The task will never come back!
    >>>>>>>>>> + */
    >>>>>>>>>> + WARN_ON(1);
    >>>>>>>>>
    >>>>>>>>> Can this condition happen to users with a non-buggy kernel?
    >>
    >>> I still haven't seen a satisfactory answer to this question. Please
    >>> don't resend patches without clearing questions raised during review.
    >>
    >> So I had a look on Friday, it _should_ not happen, but it does due to a
    >> second bug Juri is currently chasing down.
    >>
    >
    >Right, it should not happen. It happens because hotplug operations are
    >destructive w.r.t. cpusets. Peter, how about we move the check you put
    >in sched_cpu_inactive() to cpuset_cpu_inactive()? This way, if we fail,
    >we don't need to destroy/rebuild the domains.

    I remember you mentioned that there is a bug through IRC last week, if this
    patch solve it?

    Regards,
    Wanpeng Li

    >
    >Thanks,
    >
    >- Juri
    >
    >>From 65e8033e05f8b70116747062d00d5a5c266699fb Mon Sep 17 00:00:00 2001
    >From: Juri Lelli <juri.lelli@gmail.com>
    >Date: Tue, 24 Mar 2015 07:47:03 +0000
    >Subject: [PATCH] sched/core: check for available -dl bandwidth in
    > cpuset_cpu_inactive
    >
    >Signed-off-by: Juri Lelli <juri.lelli@arm.com>
    >---
    > kernel/sched/core.c | 56 ++++++++++++++++++++++++++---------------------------
    > 1 file changed, 28 insertions(+), 28 deletions(-)
    >
    >diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    >index 50927eb..3723ad0 100644
    >--- a/kernel/sched/core.c
    >+++ b/kernel/sched/core.c
    >@@ -5318,36 +5318,13 @@ static int sched_cpu_active(struct notifier_block *nfb,
    > static int sched_cpu_inactive(struct notifier_block *nfb,
    > unsigned long action, void *hcpu)
    > {
    >- unsigned long flags;
    >- long cpu = (long)hcpu;
    >- struct dl_bw *dl_b;
    >-
    > switch (action & ~CPU_TASKS_FROZEN) {
    > case CPU_DOWN_PREPARE:
    >- set_cpu_active(cpu, false);
    >-
    >- /* explicitly allow suspend */
    >- if (!(action & CPU_TASKS_FROZEN)) {
    >- bool overflow;
    >- int cpus;
    >-
    >- rcu_read_lock_sched();
    >- dl_b = dl_bw_of(cpu);
    >-
    >- raw_spin_lock_irqsave(&dl_b->lock, flags);
    >- cpus = dl_bw_cpus(cpu);
    >- overflow = __dl_overflow(dl_b, cpus, 0, 0);
    >- raw_spin_unlock_irqrestore(&dl_b->lock, flags);
    >-
    >- rcu_read_unlock_sched();
    >-
    >- if (overflow)
    >- return notifier_from_errno(-EBUSY);
    >- }
    >+ set_cpu_active((long)hcpu, false);
    > return NOTIFY_OK;
    >+ default:
    >+ return NOTIFY_DONE;
    > }
    >-
    >- return NOTIFY_DONE;
    > }
    >
    > static int __init migration_init(void)
    >@@ -7001,7 +6978,6 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
    > */
    >
    > case CPU_ONLINE:
    >- case CPU_DOWN_FAILED:
    > cpuset_update_active_cpus(true);
    > break;
    > default:
    >@@ -7013,8 +6989,32 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
    > static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
    > void *hcpu)
    > {
    >- switch (action) {
    >+ unsigned long flags;
    >+ long cpu = (long)hcpu;
    >+ struct dl_bw *dl_b;
    >+
    >+ switch (action & ~CPU_TASKS_FROZEN) {
    > case CPU_DOWN_PREPARE:
    >+ /* explicitly allow suspend */
    >+ if (!(action & CPU_TASKS_FROZEN)) {
    >+ bool overflow;
    >+ int cpus;
    >+
    >+ rcu_read_lock_sched();
    >+ dl_b = dl_bw_of(cpu);
    >+
    >+ raw_spin_lock_irqsave(&dl_b->lock, flags);
    >+ cpus = dl_bw_cpus(cpu);
    >+ overflow = __dl_overflow(dl_b, cpus, 0, 0);
    >+ raw_spin_unlock_irqrestore(&dl_b->lock, flags);
    >+
    >+ rcu_read_unlock_sched();
    >+
    >+ if (overflow) {
    >+ trace_printk("hotplug failed for cpu %lu", cpu);
    >+ return notifier_from_errno(-EBUSY);
    >+ }
    >+ }
    > cpuset_update_active_cpus(false);
    > break;
    > case CPU_DOWN_PREPARE_FROZEN:
    >--
    >2.3.0


    \
     
     \ /
      Last update: 2015-03-24 10:41    [W:3.874 / U:0.488 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site