On 07/30/2014 10:55 PM, Christoph Lameter wrote:
> On Wed, 30 Jul 2014, Fengguang Wu wrote:
>
>> FYI, this commit seems to convert some kernel boot hang bug into
>> different BUG messages.
>
> Hmmm. Still a bit confused as to why these messages occur.. Does this
> patch do any good?
The vmstat bug can't propagate to scheduler.
I also hope the following patch to be tested earlier for the vmstat bug.
>
>
> Subject: vmstat ondemand: Fix online/offline races
>
> Do not allow onlining/offlining while the shepherd task is checking
> for vmstat threads.
>
> On offlining a processor do the right thing cancelling the vmstat
> worker thread if it exista and also exclude it from the shepherd
> process checks.
>
> Signed-off-by: Christoph Lameter <c...@linux.com>
>
> Index: linux/mm/vmstat.c
> ===================================================================
> --- linux.orig/mm/vmstat.c 2014-07-30 09:35:54.602662306 -0500
> +++ linux/mm/vmstat.c 2014-07-30 09:43:07.109037043 -0500
> @@ -1317,6 +1317,7 @@ static void vmstat_shepherd(struct work_
> {
> int cpu;
>
> + get_online_cpus();
> /* Check processors whose vmstat worker threads have been disabled */
> for_each_cpu(cpu, cpu_stat_off)
> if (need_update(cpu) &&
> @@ -1325,6 +1326,7 @@ static void vmstat_shepherd(struct work_
> schedule_delayed_work_on(cpu, &per_cpu(vmstat_work,
> cpu),
> __round_jiffies_relative(sysctl_stat_interval,
> cpu));
>
> + put_online_cpus();
>
> schedule_delayed_work(&shepherd,
> round_jiffies_relative(sysctl_stat_interval));
> @@ -1380,8 +1382,8 @@ static int vmstat_cpuup_callback(struct
> break;
> case CPU_DOWN_PREPARE:
> case CPU_DOWN_PREPARE_FROZEN:
> - if (!cpumask_test_and_set_cpu(cpu, cpu_stat_off))
> - cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
> + cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
> + cpumask_clear_cpu(cpu, cpu_stat_off);
> break;
> case CPU_DOWN_FAILED:
> case CPU_DOWN_FAILED_FROZEN:
> --
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