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From: nsaenzju@redhat.com
To: Marcelo Tosatti <mtosatti@redhat.com>, linux-kernel@vger.kernel.org
Cc: Nitesh Lal <nilal@redhat.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Christoph Lameter <cl@linux.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Alex Belits <abelits@belits.com>, Peter Xu <peterx@redhat.com>
Subject: Re: [patch V3 3/8] task isolation: sync vmstats on return to userspace
Date: Fri, 10 Sep 2021 15:49:42 +0200	[thread overview]
Message-ID: <92252a92c5fe45b3ef6d2627975d917e0e522e8f.camel@redhat.com> (raw)
In-Reply-To: <20210824152646.743604666@fuller.cnet>

Hi Marcelo,

On Tue, 2021-08-24 at 12:24 -0300, Marcelo Tosatti wrote:
> The logic to disable vmstat worker thread, when entering
> nohz full, does not cover all scenarios. For example, it is possible
> for the following to happen:
> 
> 1) enter nohz_full, which calls refresh_cpu_vm_stats, syncing the stats.
> 2) app runs mlock, which increases counters for mlock'ed pages.
> 3) start -RT loop
> 
> Since refresh_cpu_vm_stats from nohz_full logic can happen _before_
> the mlock, vmstat shepherd can restart vmstat worker thread on
> the CPU in question.
> 
> To fix this, use the task isolation prctl interface to quiesce 
> deferred actions when returning to userspace.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> ---

[...]

> Index: linux-2.6/kernel/entry/common.c
> ===================================================================
> --- linux-2.6.orig/kernel/entry/common.c
> +++ linux-2.6/kernel/entry/common.c
> @@ -6,6 +6,7 @@
>  #include <linux/livepatch.h>
>  #include <linux/audit.h>
>  #include <linux/tick.h>
> +#include <linux/task_isolation.h>
>  
>  #include "common.h"
>  
> @@ -287,6 +288,7 @@ static void syscall_exit_to_user_mode_pr
>  static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
>  {
>  	syscall_exit_to_user_mode_prepare(regs);
> +	isolation_exit_to_user_mode_prepare();

Are safe from migration at this stage?

-- 
Nicolás Sáenz


  reply	other threads:[~2021-09-10 13:49 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24 15:24 [patch V3 0/8] extensible prctl task isolation interface and vmstat sync Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 1/8] add basic task isolation prctl interface Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 2/8] add prctl task isolation prctl docs and samples Marcelo Tosatti
2021-08-26  9:59   ` Frederic Weisbecker
2021-08-26 12:11     ` Marcelo Tosatti
2021-08-26 19:15       ` Christoph Lameter
2021-08-26 20:37         ` Marcelo Tosatti
2021-08-27 13:08       ` Frederic Weisbecker
2021-08-27 14:44         ` Marcelo Tosatti
2021-08-30 11:38           ` Frederic Weisbecker
2021-09-01 13:11   ` Nitesh Lal
2021-09-01 17:34     ` Marcelo Tosatti
2021-09-01 17:49       ` Nitesh Lal
2021-08-24 15:24 ` [patch V3 3/8] task isolation: sync vmstats on return to userspace Marcelo Tosatti
2021-09-10 13:49   ` nsaenzju [this message]
2021-08-24 15:24 ` [patch V3 4/8] procfs: add per-pid task isolation state Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 5/8] task isolation: sync vmstats conditional on changes Marcelo Tosatti
2021-08-25  9:46   ` Christoph Lameter
2021-08-24 15:24 ` [patch V3 6/8] KVM: x86: call isolation prepare from VM-entry code path Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 7/8] mm: vmstat: move need_update Marcelo Tosatti
2021-08-24 15:24 ` [patch V3 8/8] mm: vmstat_refresh: avoid queueing work item if cpu stats are clean Marcelo Tosatti
2021-08-25  9:30   ` Christoph Lameter
2021-09-01 13:05   ` Nitesh Lal
2021-09-01 17:32     ` Marcelo Tosatti
2021-09-01 18:33       ` Marcelo Tosatti
2021-09-03 17:38         ` Nitesh Lal
2021-08-25 10:02 ` [patch V3 0/8] extensible prctl task isolation interface and vmstat sync Marcelo Tosatti

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