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Date: Mon, 07 Jan 2013 11:39:37 +0100
From: Mike Galbraith <bitbucket@...ine.de>
To: Neil Zhang <zhangwm@...vell.com>
Cc: mingo@...nel.org, peterz@...radead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: remove redundant update_runtime notifier
On Fri, 2012-12-28 at 18:00 +0800, Neil Zhang wrote:
> migration_call() will do all the things that update_runtime() does.
> So it seems update_runtime() is a redundant notifier, remove it.
>
> Furthermore, there is potential risk that the current code will catch
> BUG_ON at line 687 of rt.c when do cpu hotplug while there are realtime
> threads running because of enable runtime twice.
Hm, box must be reading lkml behind my back.
PID: 14735 TASK: ffff880e75e86500 CPU: 4 COMMAND: "reboot"
#0 [ffff880e74b3d890] machine_kexec at ffffffff8102676e
#1 [ffff880e74b3d8e0] crash_kexec at ffffffff810a3a3a
#2 [ffff880e74b3d9b0] oops_end at ffffffff81446238
#3 [ffff880e74b3d9d0] do_invalid_op at ffffffff810035d4
#4 [ffff880e74b3da70] invalid_op at ffffffff8144d9bb
[exception RIP: __disable_runtime+494] <== BUG_ON(want);
RIP: ffffffff81045dae RSP: ffff880e74b3db28 RFLAGS: 00010082
RAX: 000000000000046a RBX: ffff880e7fcd1310 RCX: ffffffff81d88a90
RDX: 000000000000046a RSI: 0000000000000050 RDI: ffff880e7fcd19b0
RBP: ffff880e74b3db98 R8: 0000000000000010 R9: ffff88047f423408
R10: 0000000000000050 R11: ffffffff81250190 R12: 0000000000000050
R13: fffffffffde9f140 R14: ffff880e7fcd1310 R15: 000000000000122f
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#5 [ffff880e74b3dba0] rq_offline_rt at ffffffff8104b36a
#6 [ffff880e74b3dbc0] set_rq_offline at ffffffff81043c9e
#7 [ffff880e74b3dbe0] rq_attach_root at ffffffff8104c130
#8 [ffff880e74b3dc10] cpu_attach_domain at ffffffff81054f44
#9 [ffff880e74b3dc80] build_sched_domains at ffffffff81055525
#10 [ffff880e74b3dcd0] partition_sched_domains at ffffffff81055835
#11 [ffff880e74b3dd70] cpuset_cpu_inactive at ffffffff81055a0d
#12 [ffff880e74b3dd80] notifier_call_chain at ffffffff81448907
#13 [ffff880e74b3ddb0] _cpu_down at ffffffff8142b57b
#14 [ffff880e74b3de10] disable_nonboot_cpus at ffffffff8105ba23
#15 [ffff880e74b3de40] kernel_restart at ffffffff81071dde
#16 [ffff880e74b3de50] sys_reboot at ffffffff81071fc3
#17 [ffff880e74b3df80] system_call_fastpath at ffffffff8144ca12
RIP: 00007fed35778316 RSP: 00007fff23f7e198 RFLAGS: 00010202
RAX: 00000000000000a9 RBX: ffffffff8144ca12 RCX: 00007fed35771130
RDX: 0000000001234567 RSI: 0000000028121969 RDI: fffffffffee1dead
RBP: 0000000000000000 R8: 0000000000020fd0 R9: 000000000060d120
R10: 00007fff23f7df40 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
ORIG_RAX: 00000000000000a9 CS: 0033 SS: 002b
> Cc: bitbucket@...ine.de
> Signed-off-by: Neil Zhang <zhangwm@...vell.com>
> ---
> kernel/sched/core.c | 3 ---
> kernel/sched/rt.c | 40 ----------------------------------------
> kernel/sched/sched.h | 1 -
> 3 files changed, 0 insertions(+), 44 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 257002c..7b6a4d8 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6779,9 +6779,6 @@ void __init sched_init_smp(void)
> hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
> hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
>
> - /* RT runtime code needs to handle some hotplug events */
> - hotcpu_notifier(update_runtime, 0);
> -
> init_hrtick();
>
> /* Move init over to a non-isolated CPU */
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 418feb0..1a499d2 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -697,15 +697,6 @@ balanced:
> }
> }
>
> -static void disable_runtime(struct rq *rq)
> -{
> - unsigned long flags;
> -
> - raw_spin_lock_irqsave(&rq->lock, flags);
> - __disable_runtime(rq);
> - raw_spin_unlock_irqrestore(&rq->lock, flags);
> -}
> -
> static void __enable_runtime(struct rq *rq)
> {
> rt_rq_iter_t iter;
> @@ -730,37 +721,6 @@ static void __enable_runtime(struct rq *rq)
> }
> }
>
> -static void enable_runtime(struct rq *rq)
> -{
> - unsigned long flags;
> -
> - raw_spin_lock_irqsave(&rq->lock, flags);
> - __enable_runtime(rq);
> - raw_spin_unlock_irqrestore(&rq->lock, flags);
> -}
> -
> -int update_runtime(struct notifier_block *nfb, unsigned long action, void *hcpu)
> -{
> - int cpu = (int)(long)hcpu;
> -
> - switch (action) {
> - case CPU_DOWN_PREPARE:
> - case CPU_DOWN_PREPARE_FROZEN:
> - disable_runtime(cpu_rq(cpu));
> - return NOTIFY_OK;
> -
> - case CPU_DOWN_FAILED:
> - case CPU_DOWN_FAILED_FROZEN:
> - case CPU_ONLINE:
> - case CPU_ONLINE_FROZEN:
> - enable_runtime(cpu_rq(cpu));
> - return NOTIFY_OK;
> -
> - default:
> - return NOTIFY_DONE;
> - }
> -}
> -
> static int balance_runtime(struct rt_rq *rt_rq)
> {
> int more = 0;
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index fc88644..16d18a1 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -890,7 +890,6 @@ extern void sysrq_sched_debug_show(void);
> extern void sched_init_granularity(void);
> extern void update_max_interval(void);
> extern void update_group_power(struct sched_domain *sd, int cpu);
> -extern int update_runtime(struct notifier_block *nfb, unsigned long action, void *hcpu);
> extern void init_sched_rt_class(void);
> extern void init_sched_fair_class(void);
>
--
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