Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1672087

Re: [RFC PATCH-cgroup 5/6] cgroup: Skip dying css in cgroup_apply_control_{enable,disable}

Show all headers | View raw

Hello,

On Wed, Jun 14, 2017 at 11:05:36AM -0400, Waiman Long wrote:
> While constantly turning on and off controllers, it is possible to
> trigger the dying CSS warnings in cgroup_apply_control_enable() and
> cgroup_apply_control_disable(). The current code, however, proceeds
> after the warning leading to other secondary warnings and maybe even
> data corruption, like
> 
>   cgroup: cgroup_addrm_files: failed to add current, err=-17
> 
> To avoid the secondary errors, the dying CSS is now ignored or skipped
> so as not to cause other problem.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
>  kernel/cgroup/cgroup.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index f0bea32..2a5bd49 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -2846,12 +2846,24 @@ static int cgroup_apply_control_enable(struct cgroup *cgrp)
>  		for_each_subsys(ss, ssid) {
>  			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
>  
> -			WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
> -
>  			if (!(cgroup_ss_mask(dsct, false) & (1 << ss->id)) ||
>  			    (dsct->bypass_ss_mask & (1 << ss->id)))
>  				continue;
>  
> +			/*
> +			 * If the css is dying, we will just skip it after
> +			 * warning.
> +			 */
> +			if (css && (css->flags & CSS_DYING)) {
> +				char name[NAME_MAX+1];
> +
> +				cgroup_name(cgrp, name, NAME_MAX);
> +				pr_warn("%s: %s css of cgroup %s is dying!\n",
> +					__func__, ss->name, name);
> +				WARN_ON_ONCE(1);
> +				continue;
> +			}

Can you trigger this without your patches because this triggering
means that the code screwed up before it reached this point.  We
should be fixing that bug rather than masking it up here.

Thanks.

-- 
tejun

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [RFC PATCH-cgroup 5/6] cgroup: Skip dying css in  cgroup_apply_control_{enable,disable} Tejun Heo <tj@kernel.org> - 2017-06-21 23:50 +0200
  Re: [RFC PATCH-cgroup 5/6] cgroup: Skip dying css in  cgroup_apply_control_{enable,disable} Tejun Heo <tj@kernel.org> - 2017-06-22 00:10 +0200
    Re: [RFC PATCH-cgroup 5/6] cgroup: Skip dying css in  cgroup_apply_control_{enable,disable} Waiman Long <longman@redhat.com> - 2017-06-22 00:30 +0200
  Re: [RFC PATCH-cgroup 5/6] cgroup: Skip dying css in  cgroup_apply_control_{enable,disable} Waiman Long <longman@redhat.com> - 2017-06-22 00:10 +0200

csiph-web