linux-kernel - Re: [PATCH v5 01/18] cgroup/misc: Add per resource callbacks for CSS events

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Message-ID: <k4hvow3juyelizqrlwdjmuu57kscvcwanu3xhpeuqnppynzrdu@hmxuvgefqpo5>
Date:   Tue, 17 Oct 2023 20:55:02 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Haitao Huang <haitao.huang@...ux.intel.com>
Cc:     jarkko@...nel.org, dave.hansen@...ux.intel.com, tj@...nel.org,
        linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org,
        x86@...nel.org, cgroups@...r.kernel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        sohil.mehta@...el.com, zhiquan1.li@...el.com,
        kristen@...ux.intel.com, seanjc@...gle.com, zhanb@...rosoft.com,
        anakrish@...rosoft.com, mikko.ylinen@...ux.intel.com,
        yangjie@...rosoft.com
Subject: Re: [PATCH v5 01/18] cgroup/misc: Add per resource callbacks for CSS
 events

On Fri, Sep 22, 2023 at 08:06:40PM -0700, Haitao Huang <haitao.huang@...ux.intel.com> wrote:
> @@ -276,10 +276,13 @@ static ssize_t misc_cg_max_write(struct kernfs_open_file *of, char *buf,
>  
>  	cg = css_misc(of_css(of));
>  
> -	if (READ_ONCE(misc_res_capacity[type]))
> +	if (READ_ONCE(misc_res_capacity[type])) {
>  		WRITE_ONCE(cg->res[type].max, max);
> -	else
> +		if (cg->res[type].max_write)
> +			cg->res[type].max_write(cg);
> +	} else {
>  		ret = -EINVAL;
>
> +	}

Is it time for a misc_cg_mutex? This given no synchronization guarantees
to implementors of max_write. (Alternatively, document it that the
callback must implement own synchronization.)


Thanks,
Michal

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